8 S. Ct. 2206
Supreme Court of the United States
Timothy Ivory CARPENTER
v.
UNITED STATES
June 22, 2018
Roberts, C. J., delivered the opinion of the Court, in which Ginsburg, Breyer, Sotomayor, and Kagan, JJ., joined. Kennedy, J., filed a dissenting opinion, in which Thomas and Alito, JJ., joined. Thomas, J., filed a dissenting opinion. Alito, J., filed a dissenting opinion, in which Thomas, J., joined. Gorsuch, J., filed a dissenting opinion.
Chief Justice Roberts delivered the opinion of the Court.
This case presents the question whether the Government conducts a search under the Fourth Amendment when it accesses historical cell phone records that provide a comprehensive chronicle of the user’s past movements.
There are 396 million cell phone service accounts in the United States—for a Nation of 326 million people. Cell phones perform their wide and growing variety of functions by connecting to a set of radio antennas called “cell sites.” Although cell sites are usually mounted on a tower, they can also be found on light posts, flagpoles, church steeples, or the sides of buildings. Cell sites typically have several directional antennas that divide [***8] the covered area into sectors.
Cell phones continuously scan their environment looking for the best signal, which generally comes from the closest cell site. Most modern devices, such as smartphones, tap into the wireless network several times a minute whenever their signal is on, even if the owner is not using one of the phone’s features. Each time the phone connects to a cell site, it generates a time-stamped record known as cell-site location information (CSLI). The precision of this information depends on the size of the geographic area covered by the cell site. The greater the concentration of cell sites, the smaller the coverage area. As data usage from cell phones has increased, [*2212] wireless carriers have installed more cell sites to handle the traffic. That has led to increasingly compact coverage areas, especially in urban areas.
Wireless carriers collect and store CSLI for their own business purposes, including finding weak spots in their network and applying “roaming” charges when another carrier routes data through their cell sites. In addition, wireless carriers often sell aggregated location records to data brokers, without individual identifying information of the sort at [***9] issue here. While carriers have long retained CSLI for the start and end of incoming calls, in recent years phone companies have also collected location information from the transmission of text messages and routine data connections. Accordingly, modern cell phones generate increasingly vast amounts of increasingly precise CSLI.
In 2011, police officers arrested four men suspected of robbing a series of Radio Shack and (ironically enough) T-Mobile stores in Detroit. One of the men confessed that, over the previous four months, the group (along with a rotating cast of getaway drivers and lookouts) had robbed nine different stores in Michigan and Ohio. The suspect identified 15 accomplices who had participated in the heists and gave the FBI some of their cell phone numbers; the FBI then reviewed his call records to identify additional numbers that he had called around the time of the robberies.
Based on that information, the prosecutors applied for court orders under the Stored Communications Act to obtain cell phone records for petitioner Timothy Carpenter and [**516] several other suspects. That statute, as amended in 1994, permits the Government to compel the disclosure of certain telecommunications [***10] records when it “offers specific and articulable facts showing that there are reasonable grounds to believe” that the records sought “are relevant and material to an ongoing criminal investigation.” 18 U. S. C. §2703(d). Federal Magistrate Judges issued two orders directing Carpenter’s wireless carriers—MetroPCS and Sprint—to disclose “cell/site sector [information] for [Carpenter’s] telephone[ ] at call origination and at call termination for incoming and outgoing calls” during the four-month period when the string of robberies occurred. App. to Pet. for Cert. 60a, 72a. The first order sought 152 days of cell-site records from MetroPCS, which produced records spanning 127 days. The second order requested seven days of CSLI from Sprint, which produced two days of records covering the period when Carpenter’s phone was “roaming” in northeastern Ohio. Altogether the Government obtained 12,898 location points cataloging Carpenter’s movements—an average of 101 data points per day.
Carpenter was charged with six counts of robbery and an additional six counts of carrying a firearm during a federal crime of violence. See 18 U. S. C. §§924(c), 1951(a). Prior to trial, Carpenter moved to suppress the cell-site data provided by the wireless [***11] carriers. He argued that the Government’s seizure of the records violated the Fourth Amendment because they had been obtained without a warrant supported by probable cause. The District Court denied the motion. App. to Pet. for Cert. 38a-39a.
At trial, seven of Carpenter’s confederates pegged him as the leader of the operation. In addition, FBI agent Christopher Hess offered expert testimony about the cell-site data. Hess explained that each time a cell phone taps into the wireless network, the carrier logs a time-stamped record of the cell site and particular sector that were used. With this information, [*2213] Hess produced maps that placed Carpenter’s phone near four of the charged robberies. In the Government’s view, the location records clinched the case: They confirmed that Carpenter was “right where the . . . robbery was at the exact time of the robbery.” App. 131 (closing argument). Carpenter was convicted on all but one of the firearm counts and sentenced to more than 100 years in prison.
The Court of Appeals for the Sixth Circuit affirmed. 819 F. 3d 880 (2016). The court held that Carpenter lacked a reasonable expectation of privacy in the location information collected by the FBI because he had shared that information [***12] with his wireless carriers. Given that cell phone users voluntarily convey cell-site data to their carriers as “a means of establishing communication,” the court concluded that the resulting business records are not entitled to Fourth Amendment protection. Id., at 888 (quoting Smith v. Maryland, 442 U. S. 735, 741, 99 S. Ct. 2577, 61 L. Ed. 2d 220 (1979)).
We granted certiorari. 582 U. S. ___, 137 S. Ct. 2211, 198 L. Ed. 2d 657 (2017).
[1] The Fourth Amendment protects “[t]he right of the people to be secure [**517] in their persons, houses, papers, and effects, against unreasonable searches and seizures.” The “basic purpose of this Amendment,” our cases have recognized, “is to safeguard the privacy and security of individuals against arbitrary invasions by governmental officials.” Camara v. Municipal Court of City and County of San Francisco, 387 U. S. 523, 528, 87 S. Ct. 1727, 18 L. Ed. 2d 930 (1967). The Founding generation crafted the Fourth Amendment as a “response to the reviled ‘general warrants’ and ‘writs of assistance’ of the colonial era, which allowed British officers to rummage through homes in an unrestrained search for evidence of criminal activity.” Riley v. California, 573 U. S. ___, ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 452 (2014). In fact, as John Adams recalled, the patriot James Otis’s 1761 speech condemning writs of assistance was “the first act of opposition to the arbitrary claims of Great Britain” and helped spark the Revolution itself. Id., at ___-___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 452 (quoting 10 Works of John Adams 248 (C. Adams ed. 1856)).
[2] For much of our history, Fourth Amendment search doctrine was “tied to common-law [***13] trespass” and focused on whether the Government “obtains information by physically intruding on a constitutionally protected area.” United States v. Jones, 565 U. S. 400, 405, 406, n. 3, 132 S. Ct. 945, 181 L. Ed. 2d 911 (2012). More recently, the Court has recognized that “property rights are not the sole measure of Fourth Amendment violations.” Soldal v. Cook County, 506 U. S. 56, 64, 113 S. Ct. 538, 121 L. Ed. 2d 450 (1992). In Katz v. United States, 389 U. S. 347, 351, 88 S. Ct. 507, 19 L. Ed. 2d 576 (1967), we established that “the Fourth Amendment protects people, not places,” and expanded our conception of the Amendment to protect certain expectations of privacy as well. When an individual “seeks to preserve something as private,” and his expectation of privacy is “one that society is prepared to recognize as reasonable,” we have held that official intrusion into that private sphere generally qualifies as a search and requires a warrant supported by probable cause. Smith, 442 U. S., at 740, 99 S. Ct. 2577, 61 L. Ed. 2d 220 (internal quotation marks and alterations omitted).
[3] Although no single rubric definitively resolves which expectations of privacy [*2214] are entitled to protection,1 the analysis is informed by historical understandings “of what was deemed an [**518] unreasonable search and seizure when [the Fourth Amendment] was adopted.” Carroll v. United States, 267 U. S. 132, 149, 45 S. Ct. 280, 69 L. Ed. 543, T.D. 3686 (1925). On this score, our cases have recognized some basic guideposts. First, that the Amendment seeks to secure “the privacies of life” against “arbitrary power.” Boyd v. United States, 116 U. S. 616, 630, 6 S. Ct. 524, 29 L. Ed. 746 (1886). Second, and relatedly, that a central aim of the [***14] Framers was “to place obstacles in the way of a too permeating police surveillance.” United States v. Di Re, 332 U. S. 581, 595, 68 S. Ct. 222, 92 L. Ed. 210 (1948).
We have kept this attention to Founding-era understandings in mind when applying the Fourth Amendment to innovations in surveillance tools. [4] As technology has enhanced the Government’s capacity to encroach upon areas normally guarded from inquisitive eyes, this Court has sought to “assure[ ] preservation of that degree of privacy against government that existed when the Fourth Amendment was adopted.” Kyllo v. United States, 533 U. S. 27, 34, 121 S. Ct. 2038, 150 L. Ed. 2d 94 (2001). For that reason, we rejected in Kyllo a “mechanical interpretation” of the Fourth Amendment and held that use of a thermal imager to detect heat radiating from the side of the defendant’s home was a search. Id., at 35, 121 S. Ct. 2038, 150 L. Ed. 2d 94. Because any other conclusion would leave homeowners “at the mercy of advancing technology,” we determined that the Government—absent a warrant—could not capitalize on such new sense-enhancing technology to explore what was happening within the home. Ibid.
Likewise in Riley, the Court recognized the “immense storage capacity” of modern cell phones in holding that police officers must generally obtain a warrant before searching the contents of a phone. 573 U. S., at ___, 34 S. Ct. 2473, 189 L. Ed. 2d 430, 442. We explained that while the general rule allowing warrantless [***15] searches incident to arrest “strikes the appropriate balance in the context of physical objects, neither of its rationales has much force with respect to” the vast store of sensitive information on a cell phone. Id., at ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 441.
The case before us involves the Government’s acquisition of wireless carrier cell-site records revealing the location of Carpenter’s cell phone whenever it made or received calls. This sort of digital data—personal location information maintained by a third party—does not fit neatly under existing precedents. Instead, requests for cell-site records lie at the intersection of two lines of cases, both of which inform [*2215] our understanding of the privacy interests at stake.
The first set of cases addresses a person’s expectation of privacy in his physical location and movements. In United States v. Knotts, 460 U. S. 276, 103 S. Ct. 1081, 75 L. Ed. 2d 55 (1983), we considered the Government’s use of a “beeper” to aid in tracking a vehicle through traffic. Police officers in that case planted a beeper in a container of chloroform before it was purchased by one of Knotts’s co-conspirators. The officers (with intermittent aerial assistance) then followed the automobile carrying the container from Minneapolis to Knotts’s cabin in Wisconsin, relying on the beeper’s [***16] signal to help keep the [**519] vehicle in view. The Court concluded that the “augment[ed]” visual surveillance did not constitute a search because “[a] person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another.” Id., at 281, 282, 103 S. Ct. 1081, 75 L. Ed. 2d 55. Since the movements of the vehicle and its final destination had been “voluntarily conveyed to anyone who wanted to look,” Knotts could not assert a privacy interest in the information obtained. Id., at 281, 103 S. Ct. 1081, 75 L. Ed. 2d 55.
This Court in Knotts, however, was careful to distinguish between the rudimentary tracking facilitated by the beeper and more sweeping modes of surveillance. The Court emphasized the “limited use which the government made of the signals from this particular beeper” during a discrete “automotive journey.” Id., at 284, 285, 103 S. Ct. 1081, 75 L. Ed. 2d 55. Significantly, the Court reserved the question whether “different constitutional principles may be applicable” if “twenty-four hour surveillance of any citizen of this country [were] possible.” Id., at 283-284, 103 S. Ct. 1081, 75 L. Ed. 2d 55.
Three decades later, the Court considered more sophisticated surveillance of the sort envisioned in Knotts and found that different principles did indeed apply. In United States v. Jones, FBI agents installed a [***17] GPS tracking device on Jones’s vehicle and remotely monitored the vehicle’s movements for 28 days. The Court decided the case based on the Government’s physical trespass of the vehicle. 565 U. S., at 404-405, 132 S. Ct. 945, 181 L. Ed. 2d 911. At the same time, five Justices agreed that related privacy concerns would be raised by, for example, “surreptitiously activating a stolen vehicle detection system” in Jones’s car to track Jones himself, or conducting GPS tracking of his cell phone. Id., at 426, 428, 132 S. Ct. 945, 181 L. Ed. 2d 911 (Alito, J., concurring in judgment); id., at 415, 132 S. Ct. 945, 181 L. Ed. 2d 911 (Sotomayor, J., concurring). [5] Since GPS monitoring of a vehicle tracks “every movement” a person makes in that vehicle, the concurring Justices concluded that “longer term GPS monitoring in investigations of most offenses impinges on expectations of privacy”—regardless whether those movements were disclosed to the public at large. Id., at 430, 132 S. Ct. 945, 181 L. Ed. 2d 911 (opinion of Alito, J.); id., at 415, 132 S. Ct. 945, 181 L. Ed. 2d 911 (opinion of Sotomayor, J.). 2
[*2216] In a second set of decisions, the Court has drawn a line between what a person keeps to himself and what he shares with others. We have previously held that “a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties.” Smith, 442 U. S., at [**520] 743-744, 99 S. Ct. 2577, 61 L. Ed. 2d 220. That remains true “even if the information [***18] is revealed on the assumption that it will be used only for a limited purpose.” United States v. Miller, 425 U. S. 435, 443, 96 S. Ct. 1619, 48 L. Ed. 2d 71 (1976). As a result, the Government is typically free to obtain such information from the recipient without triggering Fourth Amendment protections.
This third-party doctrine largely traces its roots to Miller. While investigating Miller for tax evasion, the Government subpoenaed his banks, seeking several months of canceled checks, deposit slips, and monthly statements. The Court rejected a Fourth Amendment challenge to the records collection. For one, Miller could “assert neither ownership nor possession” of the documents; they were “business records of the banks.” Id., at 440, 96 S. Ct. 1619, 48 L. Ed. 2d 71. For another, the nature of those records confirmed Miller’s limited expectation of privacy, because the checks were “not confidential communications but negotiable instruments to be used in commercial transactions,” and the bank statements contained information “exposed to [bank] employees in the ordinary course of business.” Id., at 442, 96 S. Ct. 1619, 48 L. Ed. 2d 71. The Court thus concluded that Miller had “take[n] the risk, in revealing his affairs to another, that the information [would] be conveyed by that person to the Government.” Id., at 443, 96 S. Ct. 1619, 48 L. Ed. 2d 71.
Three years later, Smith applied the same principles in the context of information [***19] conveyed to a telephone company. The Court ruled that the Government’s use of a pen register—a device that recorded the outgoing phone numbers dialed on a landline telephone—was not a search. Noting the pen register’s “limited capabilities,” the Court “doubt[ed] that people in general entertain any actual expectation of privacy in the numbers they dial.” 442 U. S., at 742, 99 S. Ct. 2577, 61 L. Ed. 2d 220. Telephone subscribers know, after all, that the numbers are used by the telephone company “for a variety of legitimate business purposes,” including routing calls. Id., at 743, 99 S. Ct. 2577, 61 L. Ed. 2d 220. And at any rate, the Court explained, such an expectation “is not one that society is prepared to recognize as reasonable.” Ibid. (internal quotation marks omitted). When Smith placed a call, he “voluntarily conveyed” the dialed numbers to the phone company by “expos[ing] that information to its equipment in the ordinary course of business.” Id., at 744, 99 S. Ct. 2577, 61 L. Ed. 2d 220 (internal quotation marks omitted). Once again, we held that the defendant “assumed the risk” that the company’s records “would be divulged to police.” Id., at 745, 99 S. Ct. 2577, 61 L. Ed. 2d 220.
The question we confront today is how to apply the Fourth Amendment to a new phenomenon: the ability to chronicle a person’s past movements through the record of his cell phone signals. Such [***20] tracking partakes of many of the qualities of the GPS monitoring we considered in Jones. Much like GPS tracking of a vehicle, cell phone location information is detailed, encyclopedic, and effortlessly compiled.
At the same time, the fact that the individual continuously reveals his location to his wireless carrier implicates the third-party principle of [**521] Smith and Miller. But while the third-party doctrine applies to telephone numbers and bank records, it is not clear whether its logic extends to the qualitatively different category of cell-site [*2217] records. After all, when Smith was decided in 1979, few could have imagined a society in which a phone goes wherever its owner goes, conveying to the wireless carrier not just dialed digits, but a detailed and comprehensive record of the person’s movements.
We decline to extend Smith and Miller to cover these novel circumstances. [6] Given the unique nature of cell phone location records, the fact that the information is held by a third party does not by itself overcome the user’s claim to Fourth Amendment protection. Whether the Government employs its own surveillance technology as in Jones or leverages the technology of a wireless carrier, we hold that an individual [***21] maintains a legitimate expectation of privacy in the record of his physical movements as captured through CSLI. The location information obtained from Carpenter’s wireless carriers was the product of a search. 3
[7] A person does not surrender all Fourth Amendment protection by venturing into the public sphere. To the contrary, “what [one] seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.” Katz, 389 U. S., at 351-352, 88 S. Ct. 507, 19 L. Ed. 2d 576. A majority of this Court has already recognized that individuals have a reasonable expectation of privacy in the whole of their physical movements. Jones, 565 U. S., at 430, 132 S. Ct. 945, 181 L. Ed. 2d 911 (Alito, J., concurring in judgment); id., at 415, 132 S. Ct. 945, 181 L. Ed. 2d 911 (Sotomayor, J., concurring). Prior to the digital age, law enforcement might have pursued a suspect for a brief stretch, but doing so “for any extended period of time was difficult and costly and therefore rarely undertaken.” Id., at 429, 132 S. Ct. 945, 181 L. Ed. 2d 911 (opinion of Alito, J.). For that reason, “society’s expectation has been that law enforcement agents and others would not—and indeed, in the main, simply could not—secretly monitor and catalogue every single movement of an individual’s car for a very long period.” Id., at 430, 132 S. Ct. 945, 181 L. Ed. 2d 911.
Allowing government access to cell-site records contravenes that expectation. Although [***22] such records are generated for commercial purposes, that distinction does not negate Carpenter’s anticipation of privacy in his physical location. Mapping a cell phone’s location over the course of 127 days provides an all-encompassing record of the holder’s whereabouts. As [**522] with GPS information, the time-stamped data provides an intimate window into a person’s life, revealing not only his particular movements, but through them his “familial, political, professional, religious, and sexual associations.” Id., at 415, 132 S. Ct. 945, 181 L. Ed. 2d 911 (opinion of Sotomayor, J.). These location records “hold for many Americans the ‘privacies of life.’” Riley, 573 U. S., at ___,134 S. Ct. 2473, 189 L. Ed. 2d 430, 452 (quoting Boyd, 116 U. S., at 630, 6 S. Ct. 524, 29 L. Ed. 746). And like GPS monitoring, cell phone [*2218] tracking is remarkably easy, cheap, and efficient compared to traditional investigative tools. With just the click of a button, the Government can access each carrier’s deep repository of historical location information at practically no expense.
In fact, historical cell-site records present even greater privacy concerns than the GPS monitoring of a vehicle we considered in Jones. Unlike the bugged container in Knotts or the car in Jones, a cell phone—almost a “feature of human anatomy,” Riley, 573 U. S., at ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 441—tracks nearly exactly the movements of its owner. [***23] While individuals regularly leave their vehicles, they compulsively carry cell phones with them all the time. A cell phone faithfully follows its owner beyond public thoroughfares and into private residences, doctor’s offices, political headquarters, and other potentially revealing locales. See id., at ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 447 (noting that “nearly three-quarters of smart phone users report being within five feet of their phones most of the time, with 12% admitting that they even use their phones in the shower”); contrast Cardwell v. Lewis, 417 U. S. 583, 590, 94 S. Ct. 2464, 41 L. Ed. 2d 325 (1974) (plurality opinion) (“A car has little capacity for escaping public scrutiny.”). Accordingly, when the Government tracks the location of a cell phone it achieves near perfect surveillance, as if it had attached an ankle monitor to the phone’s user.
Moreover, the retrospective quality of the data here gives police access to a category of information otherwise unknowable. In the past, attempts to reconstruct a person’s movements were limited by a dearth of records and the frailties of recollection. With access to CSLI, the Government can now travel back in time to retrace a person’s whereabouts, subject only to the retention polices of the wireless carriers, which currently maintain records [***24] for up to five years. Critically, because location information is continually logged for all of the 400 million devices in the United States—not just those belonging to persons who might happen to come under investigation—this newfound tracking capacity runs against everyone. Unlike with the GPS device in Jones, police need not even know in advance whether they want to follow a particular individual, or when.
Whoever the suspect turns out to be, he has effectively been tailed every moment of every day for five years, and the police may—in the Government’s view—call upon the results of that surveillance without regard to the constraints of the Fourth Amendment. Only the few without cell phones could escape this tireless and absolute surveillance.
The Government and Justice Kennedy contend, however, that the collection of CSLI should be permitted because the data is less precise than [**523] GPS information. Not to worry, they maintain, because the location records did “not on their own suffice to place [Carpenter] at the crime scene”; they placed him within a wedge-shaped sector ranging from one-eighth to four square miles. Brief for United States 24; see post, at ___ - ___, 201 L. Ed. 2d, at 538-539. Yet [8] the Court has already rejected the [***25] proposition that “inference insulates a search.” Kyllo, 533 U. S., at 36, 121 S. Ct. 2038, 150 L. Ed. 2d 94. From the 127 days of location data it received, the Government could, in combination with other information, deduce a detailed log of Carpenter’s movements, including when he was at the site of the robberies. And the Government thought the CSLI accurate enough to highlight it during the closing argument of his trial. App. 131.
At any rate, the rule the Court adopts “must take account of more sophisticated systems that are already in use or in development.” [*2219] Kyllo, 533 U. S., at 36, 121 S. Ct. 2038, 150 L. Ed. 2d 94. While the records in this case reflect the state of technology at the start of the decade, the accuracy of CSLI is rapidly approaching GPS-level precision. As the number of cell sites has proliferated, the geographic area covered by each cell sector has shrunk, particularly in urban areas. In addition, with new technology measuring the time and angle of signals hitting their towers, wireless carriers already have the capability to pinpoint a phone’s location within 50 meters. Brief for Electronic Frontier Foundation et al. as Amici Curiae 12 (describing triangulation methods that estimate a device’s location inside a given cell sector).
Accordingly, when the Government accessed CSLI [***26] from the wireless carriers, it invaded Carpenter’s reasonable expectation of privacy in the whole of his physical movements.
The Government’s primary contention to the contrary is that the third-party doctrine governs this case. In its view, cell-site records are fair game because they are “business records” created and maintained by the wireless carriers. The Government (along with Justice Kennedy) recognizes that this case features new technology, but asserts that the legal question nonetheless turns on a garden-variety request for information from a third-party witness. Brief for United States 32-34; post, at ___ - ___, 201 L. Ed. 2d, at 535-536.
The Government’s position fails to contend with the seismic shifts in digital technology that made possible the tracking of not only Carpenter’s location but also everyone else’s, not for a short period but for years and years. Sprint Corporation and its competitors are not your typical witnesses. Unlike the nosy neighbor who keeps an eye on comings and goings, they are ever alert, and their memory is nearly infallible. There is a world of difference between the limited types of personal information addressed in Smith and Miller and the exhaustive chronicle of location [***27] information casually collected by wireless carriers today. The Government thus is not asking for a straightforward application of the third-party doctrine, but instead a significant extension of it to a distinct category of information.
[9] The third-party doctrine partly stems from the notion that an individual has a reduced expectation of [**524] privacy in information knowingly shared with another. But the fact of “diminished privacy interests does not mean that the Fourth Amendment falls out of the picture entirely.” Riley, 573 U. S., at ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 445. Smith and Miller, after all, did not rely solely on the act of sharing. Instead, they considered “the nature of the particular documents sought” to determine whether “there is a legitimate ‘expectation of privacy’ concerning their contents.” Miller, 425 U. S., at 442, 96 S. Ct. 1619, 48 L. Ed. 2d 71. Smith pointed out the limited capabilities of a pen register; as explained in Riley, telephone call logs reveal little in the way of “identifying information.” Smith, 442 U. S., at 742, 99 S. Ct. 2577, 61 L. Ed. 2d 220; Riley, 573 U. S., at ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 450. Miller likewise noted that checks were “not confidential communications but negotiable instruments to be used in commercial transactions.” 425 U. S., at 442, 96 S. Ct. 1619, 48 L. Ed. 2d 71. In mechanically applying the third-party doctrine to this case, the Government fails to appreciate that there are no comparable limitations on the revealing [***28] nature of CSLI.
The Court has in fact already shown special solicitude for location information in the third-party context. In Knotts, the Court relied on Smith to hold that an individual has no reasonable expectation of privacy in public movements that he “voluntarily [*2220] conveyed to anyone who wanted to look.” Knotts, 460 U. S., at 281, 103 S. Ct. 1081, 75 L. Ed. 2d 55; see id., at 283, 103 S. Ct. 1081, 75 L. Ed. 2d 55 (discussing Smith). But when confronted with more pervasive tracking, five Justices agreed that longer term GPS monitoring of even a vehicle traveling on public streets constitutes a search. Jones, 565 U. S., at 430, 132 S. Ct. 945, 181 L. Ed. 2d 911 (Alito, J., concurring in judgment); id., at 415, 132 S. Ct. 945, 181 L. Ed. 2d 911 (Sotomayor, J., concurring). Justice Gorsuch wonders why “someone’s location when using a phone” is sensitive, post, at ___, 201 L. Ed. 2d, at 571, and Justice Kennedy assumes that a person’s discrete movements “are not particularly private,” post, at ___, 201 L. Ed. 2d, at 538. Yet this case is not about “using a phone” or a person’s movement at a particular time. It is about a detailed chronicle of a person’s physical presence compiled every day, every moment, over several years. Such a chronicle implicates privacy concerns far beyond those considered in Smith and Miller.
Neither does the second rationale underlying the third-party doctrine—voluntary exposure—hold up when it comes to CSLI. Cell [***29] phone location information is not truly “shared” as one normally understands the term. In the first place, cell phones and the services they provide are “such a pervasive and insistent part of daily life” that carrying one is indispensable to participation in modern society. Riley, 573 U. S., at ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 441. Second, a cell phone logs a cell-site record by dint of its operation, without any affirmative act on the part of the user beyond powering up. Virtually any activity on the phone generates CSLI, including incoming calls, texts, or e-mails and countless other data connections that a phone automatically makes when checking for news, weather, or social media updates. Apart from disconnecting the phone from the network, there is no way to avoid leaving behind [**525] a trail of location data. As a result, in no meaningful sense does the user voluntarily “assume[ ] the risk” of turning over a comprehensive dossier of his physical movements. Smith, 442 U. S., at 745, 99 S. Ct. 2577, 61 L. Ed. 2d 220.
We therefore decline to extend Smith and Miller to the collection of CSLI. Given the unique nature of cell phone location information, the fact that the Government obtained the information from a third party does not overcome Carpenter’s claim to Fourth Amendment protection. The Government’s acquisition [***30] of the cell-site records was a search within the meaning of the Fourth Amendment.
***
Our decision today is a narrow one. We do not express a view on matters not before us: real-time CSLI or “tower dumps” (a download of information on all the devices that connected to a particular cell site during a particular interval). We do not disturb the application of Smith and Miller or call into question conventional surveillance techniques and tools, such as security cameras. Nor do we address other business records that might incidentally reveal location information. Further, our opinion does not consider other collection techniques involving foreign affairs or national security. As Justice Frankfurter noted when considering new innovations in airplanes and radios, the Court must tread carefully in such cases, to ensure that we do not “embarrass the future.” Northwest Airlines, Inc. v. Minnesota, 322 U. S. 292, 300, 64 S. Ct. 950, 88 L. Ed. 1283 (1944).4 [*2221]
Having found that the acquisition of Carpenter’s CSLI was a search, we also conclude that [10] the Government must generally obtain a warrant supported by probable cause before acquiring such records. Although the “ultimate measure of the constitutionality of a governmental search is ‘reasonableness,’” our cases establish that warrantless searches [***31] are typically unreasonable where “a search is undertaken by law enforcement officials to discover evidence of criminal wrongdoing.” Vernonia School Dist. 47J v. Acton, 515 U. S. 646, 652-653, 115 S. Ct. 2386, 132 L. Ed. 2d 564 (1995). Thus, “[i]n the absence of a warrant, a search is reasonable only if it falls within a specific exception to the warrant requirement.” Riley, 573 U. S., at ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 439.
The Government acquired the cell-site records pursuant to a court order issued under [11] the Stored Communications Act, which required the Government to show “reasonable grounds” for believing that the records were “relevant and material to an ongoing investigation.” 18 U. S. C. §2703(d). That showing falls well short of the probable cause required for a warrant. The Court usually requires “some quantum of individualized suspicion” before a search or seizure may take place. United States v. Martinez-Fuerte, 428 U. S. 543, 560-561, [**526] 96 S. Ct. 3074, 49 L. Ed. 2d 1116 (1976). Under the standard in the Stored Communications Act, however, law enforcement need only show that the cell-site evidence might be pertinent to an ongoing investigation—a “gigantic” departure from the probable cause rule, as the Government explained below. App. 34. Consequently, an order issued under Section 2703(d) of the Act is not a permissible mechanism for accessing historical cell-site records. Before compelling a wireless carrier to turn over a subscriber’s [***32] CSLI, the Government’s obligation is a familiar one—get a warrant.
Justice Alito contends that the warrant requirement simply does not apply when the Government acquires records using compulsory process. Unlike an actual search, he says, subpoenas for documents do not involve the direct taking of evidence; they are at most a “constructive search” conducted by the target of the subpoena. Post, at ___, 201 L. Ed. 2d, at 561. Given this lesser intrusion on personal privacy, Justice Alito argues that the compulsory production of records is not held to the same probable cause standard. In his view, this Court’s precedents set forth a categorical rule—separate and distinct from the third-party doctrine—subjecting subpoenas to lenient scrutiny without regard to the suspect’s expectation of privacy in the records. Post, at ___ - ___, 201 L. Ed. 2d, at 558-565.
But [12] this Court has never held that the Government may subpoena third parties for records in which the suspect has a reasonable expectation of privacy. Almost all of the examples Justice Alito cites, see post, at ___ - ___, 201 L. Ed. 2d, at 562-563, contemplated requests for evidence implicating diminished privacy interests or for a corporation’s own books.5 The lone exception, of course, is [*2222] Miller, where the Court’s analysis of the third-party [***33] subpoena merged with the application of the third-party doctrine. 425 U. S., at 444, 96 S. Ct. 1619, 48 L. Ed. 2d 71 (concluding that Miller lacked the necessary privacy interest to contest the issuance of a subpoena to his bank).
Justice Alito overlooks the critical issue. At some point, the dissent should recognize that [13] CSLI is an entirely different species of business record—something that implicates basic Fourth Amendment concerns about arbitrary government power much more directly than corporate tax or payroll ledgers. When confronting new concerns wrought by digital technology, this Court has been careful not to uncritically extend existing precedents. See Riley, 573 U. S., at ___, [**527] 134 S. Ct. 2473, 189 L. Ed. 2d 430, 442 (“A search of the information on a cell phone bears little resemblance to the type of brief physical search considered [in prior precedents].”).
If the choice to proceed by subpoena provided a categorical limitation on Fourth Amendment protection, no type of record would ever be protected by the warrant requirement. Under Justice Alito’s view, private letters, digital contents of a cell phone—any personal information reduced to document form, in fact—may be collected by subpoena for no reason other than “official curiosity.” United States v. Morton Salt Co., 338 U. S. 632, 652, 70 S. Ct. 357, 94 L. Ed. 401, 46 F.T.C. 1436 (1950). Justice Kennedy declines to adopt the radical implications of this theory, [***34] leaving open the question whether the warrant requirement applies “when the Government obtains the modern-day equivalents of an individual’s own ‘papers’ or ‘effects,’ even when those papers or effects are held by a third party. “ Post, at ___, 201 L. Ed. 2d, at 535 (citing United States v. Warshak, 631 F. 3d 266, 283-288 (CA6 2010)). That would be a sensible exception, because it would prevent the subpoena doctrine from overcoming any reasonable expectation of privacy. If the third-party doctrine does not apply to the “modern-day equivalents of an individual’s own ‘papers’ or ‘effects,’” then the clear implication is that the documents should receive full Fourth Amendment protection. We simply think that such protection should extend as well to a detailed log of a person’s movements over several years.
[14] This is certainly not to say that all orders compelling the production of documents will require a showing of probable cause. The Government will be able to use subpoenas to acquire records in the overwhelming majority of investigations. We hold only that a warrant is required in the rare case where the suspect has a legitimate privacy interest in records held by a third party.
Further, [15] even though the Government will generally need a warrant to access CSLI, case-specific exceptions may support [***35] a warrantless search of an individual’s cell-site records under certain circumstances. “One well-recognized exception applies when ‘ “the exigencies of the situation” make the needs of law enforcement so compelling that [a] warrantless search is objectively reasonable under the Fourth Amendment.’” Kentucky v. King, 563 U. S. 452, 460, 131 S. Ct. 1849, 179 L. Ed. 2d 865 (2011) (quoting [*2223] Mincey v. Arizona, 437 U. S. 385, 394, 98 S. Ct. 2408, 57 L. Ed. 2d 290 (1978)). Such exigencies include the need to pursue a fleeing suspect, protect individuals who are threatened with imminent harm, or prevent the imminent destruction of evidence. 563 U. S., at 460, and n. 3, 131 S. Ct. 1849, 179 L. Ed. 2d 865.
As a result, if law enforcement is confronted with an urgent situation, such fact-specific threats will likely justify the warrantless collection of CSLI. Lower courts, for instance, have approved warrantless searches related to bomb threats, active shootings, and child abductions. Our decision today does not call into doubt warrantless access to CSLI in such circumstances. While police must get a warrant when collecting CSLI to assist in the mine-run criminal investigation, the rule we set forth does not limit their ability to respond to an ongoing emergency.
[**528] ***
As Justice Brandeis explained in his famous dissent, [16] the Court is obligated—as “[s]ubtler and more far-reaching means of invading privacy have become available [***36] to the Government”—to ensure that the “progress of science” does not erode Fourth Amendment protections. Olmstead v. United States, 277 U. S. 438, 473-474, 48 S. Ct. 564, 72 L. Ed. 944 (1928). Here the progress of science has afforded law enforcement a powerful new tool to carry out its important responsibilities. At the same time, this tool risks Government encroachment of the sort the Framers, “after consulting the lessons of history,” drafted the Fourth Amendment to prevent. Di Re, 332 U. S., at 595, 68 S. Ct. 222, 92 L. Ed. 210.
[17] We decline to grant the state unrestricted access to a wireless carrier’s database of physical location information. In light of the deeply revealing nature of CSLI, its depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection, the fact that such information is gathered by a third party does not make it any less deserving of Fourth Amendment protection. The Government’s acquisition of the cell-site records here was a search under that Amendment.
The judgment of the Court of Appeals is reversed, and the case is remanded for further proceedings consistent with this opinion.
Justice Kennedy, with whom Justice Thomas and Justice Alito join, dissenting.
This case involves new technology, but the Court’s stark departure from relevant Fourth Amendment precedents and principles [***37] is, in my submission, unnecessary and incorrect, requiring this respectful dissent.
The new rule the Court seems to formulate puts needed, reasonable, accepted, lawful, and congressionally authorized criminal investigations at serious risk in serious cases, often when law enforcement seeks to prevent the threat of violent crimes. And it places undue restrictions on the lawful and necessary enforcement powers exercised not only by the Federal Government, but also by law enforcement in every State and locality throughout the Nation. Adherence to this Court’s longstanding precedents and analytic framework would have been the proper and prudent way to resolve this case.
The Court has twice held that individuals have no Fourth Amendment interests in business records which are possessed, owned, and controlled by a third party. United States v. Miller, 425 U. S. 435, 96 S. Ct. 1619, 48 L. Ed. 2d 71 (1976); Smith v. Maryland, 442 U. S. 735, 99 S. Ct. 2577, 61 L. Ed. 2d 220 (1979). This is true even when the records contain personal and sensitive information. So when the Government uses a subpoena to obtain, for [*2224] example, bank records, telephone records, and credit card statements from the businesses that create and keep these records, the Government does not engage in a search of the business’s customers within the meaning of the Fourth Amendment.
[**529] In this case petitioner challenges [***38] the Government’s right to use compulsory process to obtain a now-common kind of business record: cell-site records held by cell phone service providers. The Government acquired the records through an investigative process enacted by Congress. Upon approval by a neutral magistrate, and based on the Government’s duty to show reasonable necessity, it authorizes the disclosure of records and information that are under the control and ownership of the cell phone service provider, not its customer. Petitioner acknowledges that the Government may obtain a wide variety of business records using compulsory process, and he does not ask the Court to revisit its precedents. Yet he argues that, under those same precedents, the Government searched his records when it used court-approved compulsory process to obtain the cell-site information at issue here.
Cell-site records, however, are no different from the many other kinds of business records the Government has a lawful right to obtain by compulsory process. Customers like petitioner do not own, possess, control, or use the records, and for that reason have no reasonable expectation that they cannot be disclosed pursuant to lawful compulsory process. [***39]
The Court today disagrees. It holds for the first time that by using compulsory process to obtain records of a business entity, the Government has not just engaged in an impermissible action, but has conducted a search of the business’s customer. The Court further concludes that the search in this case was unreasonable and the Government needed to get a warrant to obtain more than six days of cell-site records.
In concluding that the Government engaged in a search, the Court unhinges Fourth Amendment doctrine from the property-based concepts that have long grounded the analytic framework that pertains in these cases. In doing so it draws an unprincipled and unworkable line between cell-site records on the one hand and financial and telephonic records on the other. According to today’s majority opinion, the Government can acquire a record of every credit card purchase and phone call a person makes over months or years without upsetting a legitimate expectation of privacy. But, in the Court’s view, the Government crosses a constitutional line when it obtains a court’s approval to issue a subpoena for more than six days of cell-site records in order to determine whether a person was within several hundred [***40] city blocks of a crime scene. That distinction is illogical and will frustrate principled application of the Fourth Amendment in many routine yet vital law enforcement operations.
It is true that the Cyber Age has vast potential both to expand and restrict individual freedoms in dimensions not contemplated in earlier times. See Packingham v. North Carolina, 582 U. S. ___, ___-___, 137 S. Ct. 1730, 198 L. Ed. 2d 273, 280 (2017). For the reasons that follow, however, there is simply no basis here for concluding that the Government interfered with information that the cell phone customer, either from a legal or commonsense standpoint, should have thought the law would deem owned or controlled by him.
Before evaluating the question presented it is helpful to understand the [**530] nature of cell-site records, how they are commonly [*2225] used by cell phone service providers, and their proper use by law enforcement.
Here the only question necessary to decide is whether the Government searched anything of Carpenter’s when it used compulsory process [***46] to obtain cell-site records from Carpenter’s cell phone service providers. This Court’s decisions in Miller and Smith dictate that the answer is no, as every Court of Appeals to have considered the question has recognized. See United States v. Thompson, 866 F. 3d 1149 (CA10 2017); United States v. Graham, 824 F. 3d 421 (CA4 2016) (en banc); Carpenter v. United States, 819 F. 3d 880 (CA6 2016); United States v. Davis, 785 F. 3d 498 (CA11 2015) (en banc); In re Application of U. S. for Historical Cell Site Data, 724 F. 3d 600 (CA5 2013).
Miller and Smith [***47] have been criticized as being based on too narrow a view of reasonable expectations of privacy. See, e.g., Ashdown, The Fourth Amendment and the “Legitimate Expectation of Privacy,” 34 Vand. L. Rev. 1289, 1313-1316 (1981). Those criticisms, however, are unwarranted. The principle established in Miller and Smith is correct for two reasons, the first relating to a defendant’s attenuated interest in property owned by another, and the second relating to the safeguards inherent in the use of compulsory process.
First, Miller and Smith placed necessary limits on the ability of individuals to assert Fourth Amendment interests in property to which they lack a “requisite connection.” Minnesota v. Carter, 525 U. S. 83, 99, 119 S. Ct. 469, 142 L. Ed. 2d 373 (1998) (Kennedy, J., concurring). Fourth Amendment rights, after all, are personal. The Amendment protects “[t]he right of the people to be secure in their . . . persons, houses, papers, and effects”—not the persons, houses, papers, and effects of others. (Emphasis added.)
Miller [***49] and Smith set forth an important and necessary limitation on the Katz framework. They rest upon the commonsense principle that the absence of property law analogues can be dispositive of privacy expectations. The defendants in those cases could expect that the third-party businesses could use the records the companies collected, stored, and classified as their own for any number of business and commercial purposes. The businesses were not bailees or custodians of the records, with a duty to hold the records for the defendants’ use. The defendants could make no argument that the records were their own papers or effects. See Miller, supra, at 440, 96 S. Ct. 1619, 48 L. Ed. 2d 71 (“the documents subpoenaed here are not respondent’s ‘private papers’”); Smith, supra, at 741, 99 S. Ct. 2577, 61 L. Ed. 2d 220 (“petitioner obviously cannot claim that his ‘property’ was invaded”). The records were the business entities’ records, plain and simple. The defendants had no reason to believe the records were owned or controlled by them and so could not assert a reasonable expectation of privacy in the records.
The second principle supporting Miller and Smith is the longstanding rule that the Government may use compulsory process to compel persons to disclose documents and other evidence within their possession [***50] and [**534] control. See United States v. Nixon, 418 U. S. 683, 709, 94 S. Ct. 3090, 41 L. Ed. 2d 1039 (1974) (it is an “ancient proposition of law” that “the public has a right to every man’s evidence” (internal quotation marks and alterations omitted)). A subpoena is different from a warrant in its force and intrusive power. While a warrant allows the Government to enter and seize and make the examination itself, a subpoena simply requires the person to whom it is directed to make the disclosure. A subpoena, moreover, provides the recipient the “opportunity to present objections” before complying, which further mitigates the intrusion. Oklahoma Press Publishing Co. v. Walling, 327 U. S. 186, 195, 66 S. Ct. 494, 90 L. Ed. 614 (1946).
For those reasons this Court has held that a subpoena for records, although a “constructive” search subject to Fourth Amendment constraints, need not comply with the procedures applicable to warrants—even when challenged by the person to whom the records belong. Id., at 202, 208, 66 S. Ct. 494, 90 L. Ed. 614. Rather, a subpoena complies with the Fourth Amendment’s reasonableness requirement so long as it is “‘sufficiently limited in scope, relevant in purpose, and specific in directive so that compliance will not be unreasonably burdensome.’” Donovan v. Lone Steer, Inc., 464 U. S. 408, 415, 104 S. Ct. 769, 78 L. Ed. 2d 567 (1984). Persons with no meaningful interests in the records sought by a subpoena, like the defendants in Miller and Smith, have no rights to object to the records’ disclosure—much [***51] less to assert that the Government must obtain a warrant to compel disclosure of the records. See Miller, 425 U. S., at 444-446, 96 S. Ct. 1619, 48 L. Ed. 2d 71; SEC v. Jerry T. O’Brien, Inc., 467 U. S. 735, 742-743, 104 S. Ct. 2720, 81 L. Ed. 2d 615 (1984).
Based on Miller and Smith and the principles underlying those cases, it is well established that subpoenas may be used to [*2229] obtain a wide variety of records held by businesses, even when the records contain private information. See 2 W. LaFave, Search and Seizure §4.13 (5th ed. 2012). Credit cards are a prime example. State and federal law enforcement, for instance, often subpoena credit card statements to develop probable cause to prosecute crimes ranging from drug trafficking and distribution to healthcare fraud to tax evasion. See United States v. Phibbs, 999 F. 2d 1053 (CA6 1993) (drug distribution); McCune v. DOJ, 592 Fed. Appx. 287 (CA5 2014) (healthcare fraud); United States v. Green, 305 F. 3d 422 (CA6 2002) (drug trafficking and tax evasion); see also 12 U. S. C. §§3402(4), 3407 (allowing the Government to subpoena financial records if “there is reason to believe that the records sought are relevant to a legitimate law enforcement inquiry”). Subpoenas also may be used to obtain vehicle registration records, hotel records, employment records, and records of utility usage, to name just a few other examples. See 1 LaFave, supra, §2.7(c).
Carpenter does not question these traditional investigative practices. And he does not ask the Court to reconsider Miller and Smith. Carpenter argues only that, under Miller and Smith, the Government may not use compulsory process to acquire cell-site records from cell phone service providers.
There is no merit in this argument. Cell-site records, like all the examples just discussed, are created, kept, classified, owned, and controlled by cell phone service providers, which aggregate and sell this information to third parties. As in Miller, Carpenter can “assert neither ownership nor possession” of the records and has no control over them. 425 U. S., at 440, 96 S. Ct. 1619, 48 L. Ed. 2d 71.
Carpenter argues that he has Fourth Amendment interests in the cell-site records because they are in essence his personal papers by operation of 47 U. S. C. §222. That statute imposes certain restrictions on how providers may use “customer proprietary network information”—a term that encompasses cell-site records. §§222(c), (h)(1)(A). The statute in general prohibits providers from disclosing personally identifiable cell-site [***53] records to private third parties. §222(c)(1). And it allows customers to request cell-site records from the provider. §222(c)(2).
Carpenter’s argument is unpersuasive, however, for §222 does not grant cell phone customers any meaningful interest in cell-site records. The statute’s confidentiality protections may be overridden by the interests of the providers or the Government. The providers may disclose the records “to protect the[ir] rights or property” or to “initiate, render, bill, and collect for telecommunications services.” §§222(d)(1), (2). They also may disclose the records “as required by law”—which, of course, is how they were disclosed in this case. §222(c)(1). Nor does the statute provide customers any practical control over the records. Customers do not create the records; they have no say in whether or for how long the records are stored; and they cannot require the records to be modified or destroyed. Even [*2230] their right to request access to the records is limited, for the statute “does not preclude a carrier from being reimbursed by the customers . . . for the costs associated with making such disclosures.” H. R. Rep. No. 104-204, pt. 1, p. 90 (1995). So in every legal and practical sense the “network information” regulated [***54] by §222 is, under that statute, “proprietary” to the service providers, not Carpenter. The Court does not argue otherwise.
Because Carpenter lacks a requisite connection to the cell-site records, he also may not claim a reasonable expectation of privacy in them. He could expect that a third party—the cell phone service provider—could use the information it collected, stored, and classified as its own for a variety of business and commercial purposes.
All this is not to say that Miller and Smith are without limits. Miller and Smith may not apply when the Government obtains the modern-day equivalents of an individual’s own “papers” or “effects,” even when those papers or effects are held by a third party. See Ex parte Jackson, 96 U. S. 727, 733, [**536] 24 L. Ed. 877 (1878) (letters held by mail carrier); United States v. Warshak, 631 F. 3d 266, 283-288 (CA6 2010) (e-mails held by Internet service provider). As already discussed, however, this case does not involve property or a bailment of that sort. Here the Government’s acquisition of cell-site records falls within the heartland of Miller and Smith.
In fact, Carpenter’s Fourth Amendment objection is even weaker than those of the defendants in Miller and Smith. Here the Government did not use a mere subpoena to obtain the cell-site records. It acquired the records only after [***55] it proved to a Magistrate Judge reasonable grounds to believe that the records were relevant and material to an ongoing criminal investigation. See 18 U. S. C. §2703(d). So even if §222 gave Carpenter some attenuated interest in the records, the Government’s conduct here would be reasonable under the standards governing subpoenas. See Donovan, 464 U. S., at 415, 104 S. Ct. 769, 78 L. Ed. 2d 567.
Under Miller and Smith, then, a search of the sort that requires a warrant simply did not occur when the Government used court-approved compulsory process, based on a finding of reasonable necessity, to compel a cell phone service provider, as owner, to disclose cell-site records.
The Court rejects a straightforward application of Miller and Smith. It concludes instead that applying those cases to cell-site records would work a “significant extension” of the principles underlying them, ante, at ___, 201 L. Ed. 2d, at 523, and holds that the acquisition of more than six days of cell-site records constitutes a search, ante, at ___, n. 3, 201 L. Ed. 2d, at 520.
In my respectful view the majority opinion misreads this Court’s precedents, old and recent, and transforms Miller and Smith into an unprincipled and unworkable doctrine. The Court’s newly conceived constitutional standard will cause confusion; will undermine traditional [***56] and important law enforcement practices; and will allow the cell phone to become a protected medium that dangerous persons will use to commit serious crimes.
The Court errs at the outset by attempting to sidestep Miller and Smith. The Court frames this case as following instead from United States v. Knotts, 460 U. S. 276, 103 S. Ct. 1081, 75 L. Ed. 2d 55 (1983), and United States v. Jones, 565 U. S. 400, 132 S. Ct. 945, 181 L. Ed. 2d 911 (2012). Those cases, the Court suggests, establish that [*2231] “individuals have a reasonable expectation of privacy in the whole of their physical movements.” Ante, at ___ - ___, ___, 201 L. Ed. 2d, at 518-520, 521.
Knotts held just the opposite: “A person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another.” 460 U. S., at 281, 103 S. Ct. 1081, 75 L. Ed. 2d 55. True, the Court in Knotts also suggested that “different constitutional principles may be applicable” to “dragnet-type law enforcement practices.” Id., at 284, 103 S. Ct. 1081, 75 L. Ed. 2d 55. But by dragnet practices the Court was referring to “‘twenty-four hour surveillance [**537] of any citizen of this country . . . without judicial knowledge or supervision.’” Id., at 283, 103 S. Ct. 1081, 75 L. Ed. 2d 55.
Those “different constitutional principles” mentioned in Knotts, whatever they may be, do not apply in this case. Here the Stored Communications Act requires a neutral judicial officer to confirm in each case that the Government has “reasonable grounds [***57] to believe” the cell-site records “are relevant and material to an ongoing criminal investigation.” 18 U. S. C. §2703(d). This judicial check mitigates the Court’s concerns about “‘a too permeating police surveillance.’” Ante, at ___, 201 L. Ed. 2d, at 518 (quoting United States v. Di Re, 332 U. S. 581, 595, 68 S. Ct. 222, 92 L. Ed. 210 (1948)). Here, even more so than in Knotts, “reality hardly suggests abuse.” 460 U. S., at 284, 103 S. Ct. 1081, 75 L. Ed. 2d 55.
The Court’s reliance on Jones fares no better. In Jones the Government installed a GPS tracking device on the defendant’s automobile. The Court held the Government searched the automobile because it “physically occupied private property [of the defendant] for the purpose of obtaining information.” 565 U. S., at 404, 132 S. Ct. 945, 181 L. Ed. 2d 911. So in Jones it was “not necessary to inquire about the target’s expectation of privacy in his vehicle’s movements.” Grady v. North Carolina, 575 U. S. ___, ___, 135 S. Ct. 1368, 191 L. Ed. 2d 459, 461 (2015) (per curiam).
But suppose the Court were correct to say that Miller and Smith rest on so imprecise a foundation. Still the Court errs, in my submission, when it concludes that cell-site records implicate greater privacy interests—and thus deserve greater Fourth Amendment protection—than financial records and telephone records.
Indeed, the opposite is true. A person’s movements are not particularly private. As the Court recognized in Knotts, when the defendant there “traveled over the public streets he voluntarily conveyed to anyone who wanted to look the fact that he was traveling over particular roads in a particular direction, the fact of whatever stops he made, and the fact of his final destination.” 460 U. S., at 281-282, 103 S. Ct. 1081, 75 L. Ed. 2d 55. Today expectations of privacy in one’s location are, if anything, even less reasonable than when the Court decided Knotts over 30 years ago. Millions [***60] of Americans choose to share their location on a daily basis, whether by using a variety of location-based services on their phones, or by sharing their location with friends and the public at large via social media.
And cell-site records, as already discussed, disclose a person’s location only in a general area. The records at issue here, for example, revealed Carpenter’s location within an area covering between around a dozen and several hundred city blocks. “Areas of this scale might encompass bridal stores and Bass Pro Shops, gay bars and straight ones, a Methodist church and the local mosque.” 819 F. 3d 880, 889 (CA6 2016). These records could not reveal where Carpenter lives and works, much less his “‘familial, political, professional, religious, and sexual associations.’” Ante, at ___, 201 L. Ed. 2d, at 522 (quoting Jones, supra, at 415, 132 S. Ct. 945, 181 L. Ed. 2d 911 (Sotomayor, J., concurring)).
By contrast, financial records and telephone records do “‘revea[l] . . . personal affairs, opinions, habits and associations.’” Miller, 425 U. S., at 451, 96 S. Ct. 1619, 48 L. Ed. 2d 71 (Brennan, J., dissenting); see Smith, 442 U. S., at 751, 99 S. Ct. 2577, 61 L. Ed. 2d 220 (Marshall, J., dissenting). What persons purchase and to whom they talk might disclose how much money they make; the political and religious organizations to which they donate; whether they have visited a psychiatrist, plastic surgeon, [***61] abortion clinic, or AIDS treatment center; whether they go to gay bars or straight ones; and who are their closest friends and family members. The troves of intimate information the Government can and does obtain using financial records and telephone records dwarfs what can be gathered from cell-site records.
Still, the Court maintains, cell-site records are “unique” because they are “comprehensive” in their reach; allow for retrospective collection; are “easy, cheap, and efficient compared to traditional [**539] investigative tools”; and are not exposed to cell phone service providers in a meaningfully voluntary manner. Ante, at ___ - ___, ___, ___, 201 L. Ed. 2d, at 520-522, 524, 527. But many other kinds of business records can be so described. Financial records are of vast scope. Banks and credit card companies keep a comprehensive account of almost every transaction an individual makes on a daily basis. “With [*2233] just the click of a button, the Government can access each [company’s] deep repository of historical [financial] information at practically no expense.” Ante, at ___ - ___, 201 L. Ed. 2d, at 522. And the decision whether to transact with banks and credit card companies is no more or less voluntary than the decision whether to use a cell phone. Today, [***62] just as when Miller was decided, “‘it is impossible to participate in the economic life of contemporary society without maintaining a bank account.’” 425 U. S., at 451, 96 S. Ct. 1619, 48 L. Ed. 2d 71 (Brennan, J., dissenting). But this Court, nevertheless, has held that individuals do not have a reasonable expectation of privacy in financial records.
Perhaps recognizing the difficulty of drawing the constitutional line between cell-site records and financial and telephonic records, the Court posits that the accuracy of cell-site records “is rapidly approaching GPS-level precision.” Ante, at ___, 201 L. Ed. 2d, at 523. That is certainly plausible in the era of cyber technology, yet the privacy interests associated with location information, which is often disclosed to the public at large, still would not outweigh the privacy interests implicated by financial and telephonic records.
Perhaps more important, those future developments are no basis upon which to resolve this case. In general, the Court “risks error by elaborating too fully on the Fourth Amendment implications of emerging technology before its role in society has become clear.” Ontario v. Quon, 560 U. S. 746, 759, 130 S. Ct. 2619, 177 L. Ed. 2d 216 (2010). That judicial caution, prudent in most cases, is imperative in this one.
Technological changes involving cell phones have complex effects [***63] on crime and law enforcement. Cell phones make crimes easier to coordinate and conceal, while also providing the Government with new investigative tools that may have the potential to upset traditional privacy expectations. See Kerr, An Equilibrium-Adjustment Theory of the Fourth Amendment, 125 Harv. L. Rev 476, 512-517 (2011). How those competing effects balance against each other, and how property norms and expectations of privacy form around new technology, often will be difficult to determine during periods of rapid technological change. In those instances, and where the governing legal standard is one of reasonableness, it is wise to defer to legislative judgments like the one embodied in §2703(d) of the Stored Communications Act. See Jones, 565 U. S., at 430, 132 S. Ct. 945, 181 L. Ed. 2d 911 (Alito, J., concurring). In §2703(d) Congress weighed the privacy interests at stake and imposed a judicial check to prevent executive overreach. The Court should be wary of upsetting that legislative balance and erecting constitutional barriers that foreclose further legislative instructions. See Quon, supra, at 759, 130 S. Ct. 2619, 177 L. Ed. 2d 216. The last thing the Court should do is incorporate [**540] an arbitrary and outside limit—in this case six days’ worth of cell-site records—and use it as the foundation for a new constitutional framework. The Court’s decision [***64] runs roughshod over the mechanism Congress put in place to govern the acquisition of cell-site records and closes off further legislative debate on these issues.
The Court says its decision is a “narrow one.” Ante, at ___, 201 L. Ed. 2d, at 525. But its reinterpretation of Miller and Smith will have dramatic consequences for law enforcement, courts, and society as a whole.
Most immediately, the Court’s holding that the Government must get a warrant to obtain more than six days of cell-site records limits the effectiveness of an important investigative tool for solving serious crimes. As this case demonstrates, cell-site records are uniquely suited to help [*2234] the Government develop probable cause to apprehend some of the Nation’s most dangerous criminals: serial killers, rapists, arsonists, robbers, and so forth. See also, e.g., Davis, 785 F. 3d, at 500-501 (armed robbers); Brief for Alabama et al. as Amici Curiae 21-22 (serial killer). These records often are indispensable at the initial stages of investigations when the Government lacks the evidence necessary to obtain a warrant. See United States v. Pembrook, 876 F. 3d 812, 816-819 (CA6 2017). And the long-term nature of many serious crimes, including serial crimes and terrorism offenses, can necessitate the use of significantly more than six [***65] days of cell-site records. The Court’s arbitrary 6-day cutoff has the perverse effect of nullifying Congress’ reasonable framework for obtaining cell-site records in some of the most serious criminal investigations.
The Court’s decision also will have ramifications that extend beyond cell-site records to other kinds of information held by third parties, yet the Court fails “to provide clear guidance to law enforcement” and courts on key issues raised by its reinterpretation of Miller and Smith. Riley v. California, 573 U. S. ___, ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 449 (2014).
First, the Court’s holding is premised on cell-site records being a “distinct category of information” from other business records. Ante, at ___, 201 L. Ed. 2d, at 523. But the Court does not explain what makes something a distinct category of information. Whether credit card records are distinct from bank records; whether payment records from digital wallet applications are distinct from either; whether the electronic bank records available today are distinct from the paper and microfilm records at issue in Miller; or whether cell-phone call records are distinct from the home-phone call records at issue in Smith, are just a few of the difficult questions that require answers under the Court’s novel conception of Miller and Smith.
[***66] Second, the majority opinion gives courts and law enforcement officers no indication how to determine whether any particular category of information falls on the financial-records side or the cell-site-records side of its newly conceived constitutional line. The Court’s multifactor analysis—considering intimacy, comprehensiveness, expense, retrospectivity, and voluntariness—puts the law on a new and unstable foundation.
[**541] Third, even if a distinct category of information is deemed to be more like cell-site records than financial records, courts and law enforcement officers will have to guess how much of that information can be requested before a warrant is required. The Court suggests that less than seven days of location information may not require a warrant. See ante, at ___, n. 3, 201 L. Ed. 2d, at 520; see also ante, at ___ - ___, 201 L. Ed. 2d, at 525 (expressing no opinion on “real-time CSLI,” tower dumps, and security-camera footage). But the Court does not explain why that is so, and nothing in its opinion even alludes to the considerations that should determine whether greater or lesser thresholds should apply to information like IP addresses or website browsing history.
Fourth, by invalidating the Government’s use of court-approved [***67] compulsory process in this case, the Court calls into question the subpoena practices of federal and state grand juries, legislatures, and other investigative bodies, as Justice Alito’s opinion explains. See post, at ___ - ___, 201 L. Ed. 2d, at 555-565 (dissenting opinion). Yet the Court fails even to mention the serious consequences this will have for the proper administration of justice.
In short, the Court’s new and uncharted course will inhibit law enforcement and “keep defendants and judges guessing for years to come.” [*2235] Riley, 573 U. S., at ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 451 (internal quotation marks omitted).
***
These reasons all lead to this respectful dissent.
This case should not turn on “whether” a search occurred. Ante, at ___, 201 L. Ed. 2d, at 515. It should turn, instead, on whose property was searched. The Fourth Amendment guarantees individuals the right to be secure from unreasonable searches of “their persons, houses, papers, and effects.” (Emphasis added.) In other words, “each person has the right to be secure against unreasonable searches . . . in his own person, house, papers, and effects.” Minnesota v. Carter, 525 U. S. 83, 92, 119 S. Ct. 469, 142 L. Ed. 2d 373 (1998) (Scalia, J., concurring). By obtaining the cell-site records of MetroPCS and Sprint, the Government did not search Carpenter’s property. He did not create the records, he does not maintain them, he cannot control them, and he cannot destroy them. Neither the terms of his contracts nor any provision of law makes the records his. The records belong to MetroPCS and Sprint.
The Court concludes [***70] that, although the records are not Carpenter’s, the Government must get a warrant because Carpenter had a reasonable “expectation of privacy” [*2236] in the location information that they reveal. Ante, at ___, 201 L. Ed. 2d, at 516. I agree with Justice Kennedy, Justice Alito, Justice Gorsuch, and every Court of Appeals to consider the question that this is not the best reading of our precedents.
The more fundamental problem with the Court’s opinion, however, is its use of the “reasonable expectation of privacy” test, which was first articulated by Justice Harlan in Katz v. United States, 389 U. S. 347, 360-361, 88 S. Ct. 507, 19 L. Ed. 2d 576 (1967) (concurring opinion). The Katz test has no basis in the text or history of the Fourth Amendment. And, it invites courts to make judgments about policy, not law. Until we confront the problems with this test, Katz will continue to distort Fourth Amendment jurisprudence. I respectfully dissent.
[omitted]
Because the Katz test is a failed experiment, this Court is dutybound to reconsider it. Until it does, I agree with my dissenting colleagues’ reading of our precedents. Accordingly, I respectfully dissent.
Justice Alito, with whom Justice Thomas joins, dissenting.
I share the Court’s concern about the effect of new technology on personal privacy, [*2247] but I fear that today’s decision will do far more harm than good. The Court’s reasoning fractures two fundamental pillars of Fourth Amendment law, and in doing so, it guarantees [***95] a blizzard of litigation while threatening many legitimate and valuable investigative practices upon which law enforcement has rightfully come to rely.
First, the Court ignores the basic distinction between an actual search (dispatching law enforcement officers to enter private premises and root through private papers and effects) and an order merely requiring a party to look through its own records and produce specified documents. The former, which intrudes on personal privacy far more deeply, requires probable cause; the latter does not. Treating an order to produce like an actual search, as today’s decision does, is revolutionary. It violates both the original understanding of the Fourth Amendment and more than a century of Supreme Court precedent. Unless it is somehow restricted to the particular situation in the present case, the Court’s move will cause upheaval. Must every grand jury subpoena duces tecum be supported by [**555] probable cause? If so, investigations of terrorism, political corruption, white-collar crime, and many other offenses will be stymied. And what about subpoenas and other document-production orders issued by administrative agencies? See, e.g., 15 U. S. C. §57b-1(c) (Federal Trade Commission); §§77s(c), 78u(a)-(b) (Securities [***96] and Exchange Commission); 29 U. S. C. §657(b) (Occupational Safety and Health Administration); 29 CFR §1601.16(a)(2) (2017) (Equal Employment Opportunity Commission).
Second, the Court allows a defendant to object to the search of a third party’s property. This also is revolutionary. The Fourth Amendment protects “[t]he right of the people to be secure in their persons, houses, papers, and effects” (emphasis added), not the persons, houses, papers, and effects of others. Until today, we have been careful to heed this fundamental feature of the Amendment’s text. This was true when the Fourth Amendment was tied to property law, and it remained true after Katz v. United States, 389 U. S. 347, 88 S. Ct. 507, 19 L. Ed. 2d 576 (1967), broadened the Amendment’s reach.
By departing dramatically from these fundamental principles, the Court destabilizes long-established Fourth Amendment doctrine. We will be making repairs—or picking up the pieces—for a long time to come.
The order in this case was the functional equivalent of a subpoena for documents, and there is no evidence that these writs were regarded as “searches” at the time of the founding. . . . .
Against centuries of precedent and practice, all that the Court can muster is the observation that “this Court has never held that the Government may subpoena third parties for records in which the suspect has a reasonable expectation of privacy.” Ante, at ___, 201 L. Ed. 2d, at 526. Frankly, I cannot imagine a concession more damning to the Court’s argument than that. As the Court well knows, the reason that we have never seen such a case is because—until today—defendants categorically had no “reasonable expectation of privacy” and no property interest in records belonging to third parties. See Part II, infra. By implying otherwise, the Court tries the nice trick of seeking shelter under the cover of precedents that it simultaneously perforates.
[*2256] Not only that, but even if the Fourth Amendment permitted someone to object to the subpoena of a third party’s records, the Court cannot explain why that individual should be entitled to greater Fourth Amendment protection than the party actually being subpoenaed. When parties are subpoenaed to turn over their records, after all, they will at most receive the protection afforded [***118] by Oklahoma Press even though they will own and have a reasonable expectation of privacy in the records at issue. Under the Court’s decision, however, the Fourth Amendment will extend greater protections to someone else who is not being subpoenaed and does not own the records. That outcome makes no sense, and the Court does not even attempt to defend it.
***
Although the majority professes a desire not to “‘embarrass the future,’” ante, at ___, 201 L. Ed. 2d, at 525, we can guess where today’s decision will lead.
One possibility is that the broad principles that the Court seems to [**570] embrace will be applied across the board. All subpoenas duces [***127] tecum and all other orders compelling [*2261] the production of documents will require a demonstration of probable cause, and individuals will be able to claim a protected Fourth Amendment interest in any sensitive personal information about them that is collected and owned by third parties. Those would be revolutionary developments indeed.
The other possibility is that this Court will face the embarrassment of explaining in case after case that the principles on which today’s decision rests are subject to all sorts of qualifications and limitations that have not yet been discovered. If we take this latter course, we will inevitably end up “mak[ing] a crazy quilt of the Fourth Amendment.” Smith, supra, at 745, 99 S. Ct. 2577, 61 L. Ed. 2d 220.
All of this is unnecessary. In the Stored Communications Act, Congress addressed the specific problem at issue in this case. The Act restricts the misuse of cell-site records by cell service providers, something that the Fourth Amendment cannot do. The Act also goes beyond current Fourth Amendment case law in restricting access by law enforcement. It permits law enforcement officers to acquire cell-site records only if they meet a heightened standard and obtain a court order. If the American people now think that the Act is inadequate or needs updating, they can turn [***128] to their elected representatives to adopt more protective provisions. Because the collection and storage of cell-site records affects nearly every American, it is unlikely that the question whether the current law requires strengthening will escape Congress’s notice.
Legislation is much preferable to the development of an entirely new body of Fourth Amendment caselaw for many reasons, including the enormous complexity of the subject, the need to respond to rapidly changing technology, and the Fourth Amendment’s limited scope. The Fourth Amendment restricts the conduct of the Federal Government and the States; it does not apply to private actors. But today, some of the greatest threats to individual privacy may come from powerful private companies that collect and sometimes misuse vast quantities of data about the lives of ordinary Americans. If today’s decision encourages the public to think that this Court can protect them from this looming threat to their privacy, the decision will mislead as well as disrupt. And if holding a provision of the Stored Communications Act to be unconstitutional dissuades Congress from further legislation in this field, the goal of protecting privacy will be greatly disserved.
The desire to make a statement [***129] about privacy in the digital age does not justify the consequences that today’s decision is likely to produce.
In the late 1960s this Court suggested for the first time that a search triggering the Fourth Amendment occurs when the government violates an “expectation of privacy” that “society is prepared to recognize as ‘reasonable.’” Katz v. United States, 389 U. S. 347, 361, 88 S. Ct. 507, 19 L. Ed. 2d 576 (1967) (Harlan, J., concurring). Then, in a pair of decisions in the 1970s applying the Katz test, the Court held that a “reasonable expectation of privacy” doesn’t attach to [**571] information shared with “third parties.” See Smith v. Maryland, 442 U. S. 735, 743-744, 99 S. Ct. 2577, 61 L. Ed. 2d 220 (1979); United States v. Miller, 425 U. S. 435, 443, 96 S. Ct. 1619, 48 L. Ed. 2d 71 (1976). By these steps, the Court came to conclude, the Constitution does nothing to limit investigators from searching records you’ve entrusted to your bank, accountant, and maybe even your doctor.
[*2262] What’s left of the Fourth Amendment? Today we use the Internet to do most everything. Smartphones make it easy to keep a calendar, correspond with friends, make calls, conduct banking, and even watch the game. Countless Internet companies maintain records about us and, increasingly, for us. Even our most private documents—those that, in other eras, we would have locked safely in a desk drawer or destroyed—now reside on third party servers. Smith and Miller [***130] teach that the police can review all of this material, on the theory that no one reasonably expects any of it will be kept private. But no one believes that, if they ever did.
What to do? It seems to me we could respond in at least three ways. The first is to ignore the problem, maintain Smith and Miller, and live with the consequences. If the confluence of these decisions and modern technology means our Fourth Amendment rights are reduced to nearly nothing, so be it. The second choice is to set Smith and Miller aside and try again using the Katz “reasonable expectation of privacy” jurisprudence that produced them. The third is to look for answers elsewhere.
*
Start with the first option. Smith held that the government’s use of a pen register to record the numbers people dial on their phones doesn’t infringe a reasonable expectation of privacy because that information is freely disclosed to the third party phone company. 442 U. S., at 743-744, 99 S. Ct. 2577, 61 L. Ed. 2d 220. Miller held that a bank account holder enjoys no reasonable expectation of privacy in the bank’s records of his account activity. That’s true, the Court reasoned, “even if the information is revealed on the assumption that it will be used only for a limited purpose and the confidence [***131] placed in the third party will not be betrayed.” 425 U. S., at 443, 96 S. Ct. 1619, 48 L. Ed. 2d 71. Today the Court suggests that Smith and Miller distinguish between kinds of information disclosed to third parties and require courts to decide whether to “extend” those decisions to particular classes of information, depending on their sensitivity. See ante, at ___ - ___, 201 L. Ed. 2d, at 520-525. But as the Sixth Circuit recognized and Justice Kennedy explains, no balancing test of this kind can be found in Smith and Miller. See ante, at ___, 201 L. Ed. 2d, at 537 (dissenting opinion). Those cases announced a categorical rule: Once you disclose information to third parties, you forfeit any reasonable expectation of privacy you might have had in it. And even if Smith and Miller did permit courts to conduct a balancing contest of the kind the Court now suggests, it’s still hard to see how that would help the petitioner in this case. Why is someone’s location when using a phone so much more sensitive than who he was talking to (Smith) or what financial transactions he engaged in (Miller)? I do not know and the Court does not say.
[**572] The problem isn’t with the Sixth Circuit’s application of Smith and Miller but with the cases themselves. Can the government demand a copy of all your e-mails [***132] from Google or Microsoft without implicating your Fourth Amendment rights? Can it secure your DNA from 23andMe without a warrant or probable cause? Smith and Miller say yes it can—at least without running afoul of Katz. But that result strikes most lawyers and judges today—me included—as pretty unlikely. In the years since its adoption, countless scholars, too, have come to conclude that the “third-party doctrine is not only wrong, but horribly wrong.” Kerr, The Case for the Third-Party Doctrine, 107 Mich. L. Rev. 561, 563, n. 5, 564 (2009) (collecting criticisms but defending the doctrine (footnotes omitted)). The reasons are obvious. “As an empirical statement about subjective [*2263] expectations of privacy,” the doctrine is “quite dubious.” Baude & Stern, The Positive Law Model of the Fourth Amendment, 129 Harv. L. Rev. 1821, 1872 (2016). People often do reasonably expect that information they entrust to third parties, especially information subject to confidentiality agreements, will be kept private. Meanwhile, if the third party doctrine is supposed to represent a normative assessment of when a person should expect privacy, the notion that the answer might be “never” seems a pretty unattractive societal prescription. Ibid.
What, then, is the explanation for our third party doctrine? The [***133] truth is, the Court has never offered a persuasive justification. The Court has said that by conveying information to a third party you “‘assum[e] the risk’” it will be revealed to the police and therefore lack a reasonable expectation of privacy in it. Smith, supra, at 744, 99 S. Ct. 2577, 61 L. Ed. 2d 220. But assumption of risk doctrine developed in tort law. It generally applies when “by contract or otherwise [one] expressly agrees to accept a risk of harm” or impliedly does so by “manifest[ing] his willingness to accept” that risk and thereby “take[s] his chances as to harm which may result from it.” Restatement (Second) of Torts §§496B, 496C(1), and Comment b (1965); see also 1 D. Dobbs, P. Hayden, & E. Bublick, Law of Torts §§235-236, pp. 841-850 (2d ed. 2017). That rationale has little play in this context. Suppose I entrust a friend with a letter and he promises to keep it secret until he delivers it to an intended recipient. In what sense have I agreed to bear the risk that he will turn around, break his promise, and spill its contents to someone else? More confusing still, what have I done to “manifest my willingness to accept” the risk that the government will pry the document from my friend and read it without his consent?
One possible answer concerns knowledge. I know that my friend [***134] might break his promise, or that the government might have some reason to search the papers in his possession. But knowing about a risk doesn’t mean you assume responsibility for it. Whenever you walk down the sidewalk you know a car may negligently or recklessly veer off and hit you, but that hardly means you accept the consequences and absolve the driver of any damage he may do to you. Epstein, Privacy and the Third Hand: Lessons From the Common Law of Reasonable Expectations, 24 Berkeley Tech. L. J. 1199, 1204 (2009); see W. Keeton, D. Dobbs, R. Keeton, & D. [**573] Owen, Prosser & Keeton on Law of Torts 490 (5th ed. 1984).
Some have suggested the third party doctrine is better understood to rest on consent than assumption of risk. “So long as a person knows that they are disclosing information to a third party,” the argument goes, “their choice to do so is voluntary and the consent valid.” Kerr, supra, at 588. I confess I still don’t see it. Consenting to give a third party access to private papers that remain my property is not the same thing as consenting to a search of those papers by the government. Perhaps there are exceptions, like when the third party is an undercover government agent. See Murphy, The Case Against the Case Against the Third-Party [***135] Doctrine: A Response to Epstein and Kerr, 24 Berkeley Tech. L. J. 1239, 1252 (2009); cf. Hoffa v. United States, 385 U. S. 293, 87 S. Ct. 408, 17 L. Ed. 2d 374 (1966). But otherwise this conception of consent appears to be just assumption of risk relabeled—you’ve “consented” to whatever risks are foreseeable.
Another justification sometimes offered for third party doctrine is clarity. You (and the police) know exactly how much protection you have in information confided [*2264] to others: none. As rules go, “the king always wins” is admirably clear. But the opposite rule would be clear too: Third party disclosures never diminish Fourth Amendment protection (call it “the king always loses”). So clarity alone cannot justify the third party doctrine.
In the end, what do Smith and Miller add up to? A doubtful application of Katz that lets the government search almost whatever it wants whenever it wants. The Sixth Circuit had to follow that rule and faithfully did just that, but it’s not clear why we should.
*
There’s a second option. What if we dropped Smith and Miller’s third party doctrine and retreated to the root Katz question whether there is a “reasonable expectation of privacy” in data held by third parties? Rather than solve the problem with the third party doctrine, I worry this option only risks returning us to its source: [***136] After all, it was Katz that produced Smith and Miller in the first place.
Katz’s problems start with the text and original understanding of the Fourth Amendment, as Justice Thomas thoughtfully explains today. Ante, at ___ - ___, 201 L. Ed. 2d, at 544-551 (dissenting opinion). The Amendment’s protections do not depend on the breach of some abstract “expectation of privacy” whose contours are left to the judicial imagination. Much more concretely, it protects your “person,” and your “houses, papers, and effects.” Nor does your right to bring a Fourth Amendment claim depend on whether a judge happens to agree that your subjective expectation to privacy is a “reasonable” one. Under its plain terms, the Amendment grants you the right to invoke its guarantees whenever one of your protected things (your person, your house, your papers, or your effects) is unreasonably searched or seized. Period.
History too holds problems for Katz. Little like it can be found in the law that led to the adoption of the Fourth Amendment or in this Court’s jurisprudence until the late 1960s. The Fourth Amendment came about in [**574] response to a trio of 18th century cases “well known to the men who wrote and ratified the Bill of Rights, [and] famous throughout the colonial population.” Stuntz, The Substantive Origins of Criminal Procedure, [***137] 105 Yale L. J. 393, 397 (1995). The first two were English cases invalidating the Crown’s use of general warrants to enter homes and search papers. Entick v. Carrington, 19 How. St. Tr. 1029 (K. B. 1765); Wilkes v. Wood, 19 How. St. Tr. 1153 (K. B. 1763); see W. Cuddihy, The Fourth Amendment: Origins and Original Meaning 439-487 (2009); Boyd v. United States, 116 U. S. 616, 625-630, 6 S. Ct. 524, 29 L. Ed. 746 (1886). The third was American: the Boston Writs of Assistance Case, which sparked colonial outrage at the use of writs permitting government agents to enter houses and business, breaking open doors and chests along the way, to conduct searches and seizures—and to force third parties to help them. Stuntz, supra, at 404-409; M. Smith, The Writs of Assistance Case (1978). No doubt the colonial outrage engendered by these cases rested in part on the government’s intrusion upon privacy. But the framers chose not to protect privacy in some ethereal way dependent on judicial intuitions. They chose instead to protect privacy in particular places and things—”persons, houses, papers, and effects”—and against particular threats—”unreasonable” governmental “searches and seizures.” See Entick, supra, at 1066 (“Papers are the owner’s goods and chattels; they are his dearest property; and so far from enduring a seizure, that they will hardly bear an inspection”); see also ante, at ___ - ___, 201 L. Ed. 2d, at 551-554 (Thomas, J., dissenting).
[*2265] Even taken on its own terms, Katz has never been sufficiently [***138] justified. In fact, we still don’t even know what its “reasonable expectation of privacy” test is. Is it supposed to pose an empirical question (what privacy expectations do people actually have) or a normative one (what expectations should they have)? Either way brings problems. If the test is supposed to be an empirical one, it’s unclear why judges rather than legislators should conduct it. Legislators are responsive to their constituents and have institutional resources designed to help them discern and enact majoritarian preferences. Politically insulated judges come armed with only the attorneys’ briefs, a few law clerks, and their own idiosyncratic experiences. They are hardly the representative group you’d expect (or want) to be making empirical judgments for hundreds of millions of people. Unsurprisingly, too, judicial judgments often fail to reflect public views. See Slobogin & Schumacher, Reasonable Expectations of Privacy and Autonomy in Fourth Amendment Cases: An Empirical Look at “Understandings Recognized and Permitted by Society,” 42 Duke L. J. 727, 732, 740-742 (1993). Consider just one example. Our cases insist that the seriousness of the offense being investigated does not reduce Fourth Amendment protection. Mincey v. Arizona, 437 U. S. 385, 393-394, 98 S. Ct. 2408, 57 L. Ed. 2d 290 (1978). Yet scholars suggest that [***139] most people are more tolerant of police intrusions when they investigate more serious crimes. See Blumenthal, Adya, & Mogle, The Multiple Dimensions of Privacy: Testing Lay “Expectations of Privacy,” 11 U. Pa. J. Const. L. 331, 352-353 (2009). And I very much doubt that this Court would be [**575] willing to adjust its Katz cases to reflect these findings even if it believed them.
Maybe, then, the Katz test should be conceived as a normative question. But if that’s the case, why (again) do judges, rather than legislators, get to determine whether society should be prepared to recognize an expectation of privacy as legitimate? Deciding what privacy interests should be recognized often calls for a pure policy choice, many times between incommensurable goods—between the value of privacy in a particular setting and society’s interest in combating crime. Answering questions like that calls for the exercise of raw political will belonging to legislatures, not the legal judgment proper to courts. See The Federalist No. 78, p. 465 (C. Rossiter ed. 1961) (A. Hamilton). When judges abandon legal judgment for political will we not only risk decisions where “reasonable expectations of privacy” come to bear “an uncanny resemblance to those expectations [***140] of privacy” shared by Members of this Court. Minnesota v. Carter, 525 U. S. 83, 97, 119 S. Ct. 469, 142 L. Ed. 2d 373 (1998) (Scalia, J., concurring). We also risk undermining public confidence in the courts themselves.
My concerns about Katz come with a caveat. Sometimes, I accept, judges may be able to discern and describe existing societal norms. See, e.g., Florida v. Jardines, 569 U. S. 1, 8, 133 S. Ct. 1409, 185 L. Ed. 2d 495 (2013) (inferring a license to enter on private property from the “‘habits of the country’” (quoting McKee v. Gratz, 260 U. S. 127, 136, 43 S. Ct. 16, 67 L. Ed. 167 (1922))); Sachs, Finding Law, 107 Cal. L. Rev. (forthcoming 2019), online at https://ssrn.com/ abstract=3064443 (as last visited June 19, 2018). That is particularly true when the judge looks to positive law rather than intuition for guidance on social norms. See Byrd v. United States, 584 U. S. ___, ___-___, 138 S. Ct. 1518, 200 L. Ed. 2d 805, 809 (2018) (“general property-based concept[s] guid[e] the resolution of this case”). So there may be some occasions where Katz is capable of principled application— [*2266] though it may simply wind up approximating the more traditional option I will discuss in a moment. Sometimes it may also be possible to apply Katz by analogizing from precedent when the line between an existing case and a new fact pattern is short and direct. But so far this Court has declined to tie itself to any significant restraints like these. See ante, at ___, n. 1, 201 L. Ed. 2d, at 517 (“[W]hile property rights are often informative, [***141] our cases by no means suggest that such an interest is ‘fundamental’ or ‘dispositive’ in determining which expectations of privacy are legitimate”).
As a result, Katz has yielded an often unpredictable—and sometimes unbelievable—jurisprudence. Smith and Miller are only two examples; there are many others. Take Florida v. Riley, 488 U. S. 445, 109 S. Ct. 693, 102 L. Ed. 2d 835 (1989), which says that a police helicopter hovering 400 feet above a person’s property invades no reasonable expectation of privacy. Try that one out on your neighbors. Or California v. Greenwood, 486 U. S. 35, 108 S. Ct. 1625, 100 L. Ed. 2d 30 (1988), which holds that a person has no reasonable expectation of privacy in the garbage he puts out for collection. In that case, the Court said that the homeowners forfeited their privacy interests because “[i]t is common [**576] knowledge that plastic garbage bags left on or at the side of a public street are readily accessible to animals, children, scavengers, snoops, and other members of the public.” Id., at 40, 108 S. Ct. 1625, 100 L. Ed. 2d 30 (footnotes omitted). But the habits of raccoons don’t prove much about the habits of the country. I doubt, too, that most people spotting a neighbor rummaging through their garbage would think they lacked reasonable grounds to confront the rummager. Making the decision all the stranger, California state law expressly protected [***142] a homeowner’s property rights in discarded trash. Id., at 43, 108 S. Ct. 1625, 100 L. Ed. 2d 30. Yet rather than defer to that as evidence of the people’s habits and reasonable expectations of privacy, the Court substituted its own curious judgment.
Resorting to Katz in data privacy cases threatens more of the same. Just consider. The Court today says that judges should use Katz’s reasonable expectation of privacy test to decide what Fourth Amendment rights people have in cell-site location information, explaining that “no single rubric definitively resolves which expectations of privacy are entitled to protection.” Ante, at ___, 201 L. Ed. 2d, at 517. But then it offers a twist. Lower courts should be sure to add two special principles to their Katz calculus: the need to avoid “arbitrary power” and the importance of “plac[ing] obstacles in the way of a too permeating police surveillance.” Ante, at ___, 201 L. Ed. 2d, at 517 (internal quotation marks omitted). While surely laudable, these principles don’t offer lower courts much guidance. The Court does not tell us, for example, how far to carry either principle or how to weigh them against the legitimate needs of law enforcement. At what point does access to electronic data amount to “arbitrary” authority? When does police surveillance become [***143] “too permeating”? And what sort of “obstacles” should judges “place” in law enforcement’s path when it does? We simply do not know.
The Court’s application of these principles supplies little more direction. The Court declines to say whether there is any sufficiently limited period of time “for which the Government may obtain an individual’s historical [location information] free from Fourth Amendment scrutiny.” Ante, at ___, n. 3, 201 L. Ed. 2d, at 521; see ante, at ___ - ___, 201 L. Ed. 2d, at 520-523. But then it tells us that access to seven days’ worth of information does trigger Fourth Amendment scrutiny—even though here the carrier “produced only two days of records.” Ante, at ___, n. 3, 201 L. Ed. 2d, at 521. Why is the relevant fact the seven days of [*2267] information the government asked for instead of the two days of information the government actually saw? Why seven days instead of ten or three or one? And in what possible sense did the government “search” five days’ worth of location information it was never even sent? We do not know.
Later still, the Court adds that it can’t say whether the Fourth Amendment is triggered when the government collects “real-time CSLI or ‘tower dumps’ (a download of information on all the devices that connected to a particular cell site during a particular interval).” Ante, at ___ - ___, 201 L. Ed. 2d, at 525 [***144] . But what distinguishes historical data from real-time data, or seven days of a single person’s data from a download of everyone’s data over some indefinite period [**577] of time? Why isn’t a tower dump the paradigmatic example of “too permeating police surveillance” and a dangerous tool of “arbitrary” authority—the touchstones of the majority’s modified Katz analysis? On what possible basis could such mass data collection survive the Court’s test while collecting a single person’s data does not? Here again we are left to guess. At the same time, though, the Court offers some firm assurances. It tells us its decision does not “call into question conventional surveillance techniques and tools, such as security cameras.” Ibid. That, however, just raises more questions for lower courts to sort out about what techniques qualify as “conventional” and why those techniques would be okay even if they lead to “permeating police surveillance” or “arbitrary police power.”
Nor is this the end of it. After finding a reasonable expectation of privacy, the Court says there’s still more work to do. Courts must determine whether to “extend” Smith and Miller to the circumstances before them. Ante, at ___, ___ - ___, 201 L. Ed. 2d, at 521, 523-525 [***145] . So apparently Smith and Miller aren’t quite left for dead; they just no longer have the clear reach they once did. How do we measure their new reach? The Court says courts now must conduct a second Katz-like balancing inquiry, asking whether the fact of disclosure to a third party outweighs privacy interests in the “category of information” so disclosed. Ante, at ___, ___ - ___, 201 L. Ed. 2d, at 522, 523-524. But how are lower courts supposed to weigh these radically different interests? Or assign values to different categories of information? All we know is that historical cell-site location information (for seven days, anyway) escapes Smith and Miller’s shorn grasp, while a lifetime of bank or phone records does not. As to any other kind of information, lower courts will have to stay tuned.
In the end, our lower court colleagues are left with two amorphous balancing tests, a series of weighty and incommensurable principles to consider in them, and a few illustrative examples that seem little more than the product of judicial intuition. In the Court’s defense, though, we have arrived at this strange place not because the Court has misunderstood Katz. Far from it. We have arrived here because this is where Katz inevitably leads.
*
There is another way. From the founding until the 1960s, the right to assert a Fourth Amendment claim didn’t depend on your ability to appeal to a judge’s personal sensibilities about the “reasonableness” of your expectations or privacy. It was tied to the law. Jardines, 569 U. S., at 11, 133 S. Ct. 1409, 185 L. Ed. 2d 495; United States v. Jones, 565 U. S. 400, 405, 132 S. Ct. 945, 181 L. Ed. 2d 911 (2012). The Fourth Amendment protects “the right of the people to be secure in their persons, houses, papers and effects, against unreasonable searches and seizures.” True to those words and their original understanding, the traditional approach [*2268] asked if a house, paper or effect was yours under law. No more was needed to [***146] trigger the Fourth Amendment. Though now often lost in Katz’s shadow, this traditional understanding persists. Katz only “supplements, rather than displaces the traditional property-based understanding of the Fourth Amendment.” Byrd, 584 U. S., at ___, 138 S. Ct. [**578] 1518, 200 L. Ed. 2d 805, 814 (internal quotation marks omitted); Jardines, supra, at 11, 133 S. Ct. 1409, 185 L. Ed. 2d 495 (same); Soldal v. Cook County, 506 U. S. 56, 64, 113 S. Ct. 538, 121 L. Ed. 2d 450 (1992) (Katz did not “snuf[f ] out the previously recognized protection for property under the Fourth Amendment”).
Beyond its provenance in the text and original understanding of the Amendment, this traditional approach comes with other advantages. Judges are supposed to decide cases based on “democratically legitimate sources of law”—like positive law or analogies to items protected by the enacted Constitution—rather than “their own biases or personal policy preferences.” Pettys, Judicial Discretion in Constitutional Cases, 26 J. L. & Pol. 123, 127 (2011). A Fourth Amendment model based on positive legal rights “carves out significant room for legislative participation in the Fourth Amendment context,” too, by asking judges to consult what the people’s representatives have to say about their rights. Baude & Stern, 129 Harv. L. Rev., at 1852. Nor is this approach hobbled by Smith and Miller, for those cases are just limitations on Katz, addressing only the question whether individuals have a reasonable expectation of privacy in materials they share with [***147] third parties. Under this more traditional approach, Fourth Amendment protections for your papers and effects do not automatically disappear just because you share them with third parties.
Given the prominence Katz has claimed in our doctrine, American courts are pretty rusty at applying the traditional approach to the Fourth Amendment. We know that if a house, paper, or effect is yours, you have a Fourth Amendment interest in its protection. But what kind of legal interest is sufficient to make something yours? And what source of law determines that? Current positive law? The common law at 1791, extended by analogy to modern times? Both? See Byrd, supra, at ___-___, 138 S. Ct. 1518, 200 L. Ed. 2d 805, 819 (Thomas, J., concurring); cf. Re, The Positive Law Floor, 129 Harv. L. Rev. Forum 313 (2016). Much work is needed to revitalize this area and answer these questions. I do not begin to claim all the answers today, but (unlike with Katz) at least I have a pretty good idea what the questions are. And it seems to me a few things can be said.
First, the fact that a third party has access to or possession of your papers and effects does not necessarily eliminate your interest in them. Ever hand a private document to a friend to be returned? Toss your keys to a valet at a restaurant? Ask your neighbor to look after your dog while you travel? You would not expect [***148] the friend to share the document with others; the valet to lend your car to his buddy; or the neighbor to put Fido up for adoption. Entrusting your stuff to others is a bailment. A bailment is the “delivery of personal property by one person (the bailor) to another (the bailee) who holds the property for a certain purpose.” Black’s Law Dictionary 169 (10th ed. 2014); J. Story, Commentaries on the Law of Bailments §2, p. 2 (1832) (“a bailment is a delivery of a thing in trust for some special object or purpose, and upon a contract, expressed or implied, to conform to the object or purpose of the trust”). A bailee normally owes a legal duty to keep the item safe, according to the [**579] terms of the parties’ contract if they have one, and according to the “implication[s] from their [*2269] conduct” if they don’t. 8 C. J. S., Bailments §36, pp. 468-469 (2017). A bailee who uses the item in a different way than he’s supposed to, or against the bailor’s instructions, is liable for conversion. Id., §43, at 481; see Goad v. Harris, 207 Ala. 357, 92 So. 546, (1922); Knight v. Seney, 290 Ill. 11, 17, 124 N. E. 813, 815-816 (1919); Baxter v. Woodward, 191 Mich. 379, 385, 158 N. W. 137, 139 (1916). This approach is quite different from Smith and Miller’s (counter)-intuitive approach to reasonable expectations of privacy; where those cases extinguish Fourth Amendment interests once records are given to a [***149] third party, property law may preserve them.
Our Fourth Amendment jurisprudence already reflects this truth. In Ex parte Jackson, 96 U. S. 727, 24 L. Ed. 877 (1878), this Court held that sealed letters placed in the mail are “as fully guarded from examination and inspection, except as to their outward form and weight, as if they were retained by the parties forwarding them in their own domiciles.” Id., at 733, 24 L. Ed. 877. The reason, drawn from the Fourth Amendment’s text, was that “[t]he constitutional guaranty of the right of the people to be secure in their papers against unreasonable searches and seizures extends to their papers, thus closed against inspection, wherever they may be.” Ibid. (emphasis added). It did not matter that letters were bailed to a third party (the government, no less). The sender enjoyed the same Fourth Amendment protection as he does “when papers are subjected to search in one’s own household.” Ibid.
These ancient principles may help us address modern data cases too. Just because you entrust your data—in some cases, your modern-day papers and effects—to a third party may not mean you lose any Fourth Amendment interest in its contents. Whatever may be left of Smith and Miller, few doubt that e-mail should be treated much like the traditional mail it has largely supplanted—as a bailment in which [***150] the owner retains a vital and protected legal interest. See ante, at ___, 201 L. Ed. 2d, at 535 (Kennedy, J., dissenting) (noting that enhanced Fourth Amendment protection may apply when the “modern-day equivalents of an individual’s own ‘papers’ or ‘effects’ . . . are held by a third party” through “bailment”); ante, at ___, n. 6, 201 L. Ed. 2d, at 568 (Alito, J., dissenting) (reserving the question whether Fourth Amendment protection may apply in the case of “bailment” or when “someone has entrusted papers he or she owns . . . to the safekeeping of another”); United States v. Warshak, 631 F. 3d 266, 285-286 (CA6 2010) (relying on an analogy to Jackson to extend Fourth Amendment protection to e-mail held by a third party service provider).
Second, I doubt that complete ownership or exclusive control of property is always a necessary condition to the assertion of a Fourth Amendment right. Where houses are concerned, for example, individuals can enjoy Fourth Amendment protection without fee simple title. Both the text of the Amendment and the common law rule support that conclusion. “People call a house ‘their’ home when legal title is in the bank, when they rent it, and even when they merely occupy it rent free.” Carter, 525 U. S., at 95-96, 119 S. Ct. 469, 142 L. Ed. 2d 373 [**580] (Scalia, J., concurring). That rule derives from the common law. Oystead v. Shed, 13 Mass. 520, 523 (1816) (explaining, citing “[t]he very learned judges, Foster, Hale, and Coke,” that the law “would [***151] be as much disturbed by a forcible entry to arrest a boarder or a servant, who had acquired, by contract, express or implied, a right to enter the house at all times, and to remain in it as long as they please, as if the object were to arrest the master of the house or his children”). That is why tenants and resident family members—though they have no legal title—have standing to complain [*2270] about searches of the houses in which they live. Chapman v. United States, 365 U. S. 610, 616-617, 81 S. Ct. 776, 5 L. Ed. 2d 828 (1961), Bumper v. North Carolina, 391 U. S. 543, 548, n. 11, 88 S. Ct. 1788, 20 L. Ed. 2d 797 (1968).
Another point seems equally true: just because you have to entrust a third party with your data doesn’t necessarily mean you should lose all Fourth Amendment protections in it. Not infrequently one person comes into possession of someone else’s property without the owner’s consent. Think of the finder of lost goods or the policeman who impounds a car. The law recognizes that the goods and the car still belong to their true owners, for “where a person comes into lawful possession of the personal property of another, even though there is no formal agreement between the property’s owner and its possessor, the possessor will become a constructive bailee when justice so requires.” Christensen v. Hoover, 643 P. 2d 525, 529 (Colo. 1982) (en banc); Laidlaw, Principles of Bailment, 16 Cornell L. Q. 286 (1931). At least some of this Court’s decisions [***152] have already suggested that use of technology is functionally compelled by the demands of modern life, and in that way the fact that we store data with third parties may amount to a sort of involuntary bailment too. See ante, at ___ - ___, 201 L. Ed. 2d, at 521-522 (majority opinion); Riley v. California, 573 U. S. ___, ___, 134 S. Ct. 2473, 189 L. Ed. 2d 430, 441 (2014).
Third, positive law may help provide detailed guidance on evolving technologies without resort to judicial intuition. State (or sometimes federal) law often creates rights in both tangible and intangible things. See Ruckelshaus v. Monsanto Co., 467 U. S. 986, 1001, 104 S. Ct. 2862, 81 L. Ed. 2d 815 (1984). In the context of the Takings Clause we often ask whether those state-created rights are sufficient to make something someone’s property for constitutional purposes. See id., at 1001-1003, 104 S. Ct. 2862, 81 L. Ed. 2d 815; Louisville Joint Stock Land Bank v. Radford, 295 U. S. 555, 590-595, 55 S. Ct. 854, 79 L. Ed. 1593 (1935). A similar inquiry may be appropriate for the Fourth Amendment. Both the States and federal government are actively legislating in the area of third party data storage and the rights users enjoy. See, e.g., Stored Communications Act, 18 U. S. C. §2701 et seq.; Tex. Prop. Code Ann. §111.004(12) (West 2017) (defining “[p]roperty” to include “property held in any digital or electronic medium”). State courts are busy expounding common law property principles in this area as well. E.g., Ajemian v. Yahoo!, Inc., 478 Mass. 169, 170, 84 N. E. 3d 766, 768 (2017) (e-mail account is a “form of property often referred to as a ‘digital asset’”); Eysoldt v. ProScan Imaging, 194 Ohio App. 3d 630, 638, 2011-Ohio-2359, 957 N. E. 2d 780, 786 (2011) (permitting [**581] action for conversion of web account as intangible property). [***153] If state legislators or state courts say that a digital record has the attributes that normally make something property, that may supply a sounder basis for judicial decisionmaking than judicial guesswork about societal expectations.
Fourth, while positive law may help establish a person’s Fourth Amendment interest there may be some circumstances where positive law cannot be used to defeat it. Ex parte Jackson reflects that understanding. There this Court said that “[n]o law of Congress” could authorize letter carriers “to invade the secrecy of letters.” 96 U. S., at 733, 24 L. Ed. 877. So the post office couldn’t impose a regulation dictating that those mailing letters surrender all legal interests in them once they’re deposited in a mailbox. If that is right, Jackson suggests the existence of a constitutional floor below which Fourth Amendment rights may not descend. Legislatures cannot [*2271] pass laws declaring your house or papers to be your property except to the extent the police wish to search them without cause. As the Court has previously explained, “we must ‘assur[e] preservation of that degree of privacy against government that existed when the Fourth Amendment was adopted.’” Jones, 565 U. S., at 406, 132 S. Ct. 945, 181 L. Ed. 2d 911 (quoting Kyllo v. United States, 533 U. S. 27, 34, 121 S. Ct. 2038, 150 L. Ed. 2d 94 (2001)). Nor does this mean protecting only the specific rights known at the [***154] founding; it means protecting their modern analogues too. So, for example, while thermal imaging was unknown in 1791, this Court has recognized that using that technology to look inside a home constitutes a Fourth Amendment “search” of that “home” no less than a physical inspection might. Id., at 40, 121 S. Ct. 2038, 150 L. Ed. 2d 94.
Fifth, this constitutional floor may, in some instances, bar efforts to circumvent the Fourth Amendment’s protection through the use of subpoenas. No one thinks the government can evade Jackson’s prohibition on opening sealed letters without a warrant simply by issuing a subpoena to a postmaster for “all letters sent by John Smith” or, worse, “all letters sent by John Smith concerning a particular transaction.” So the question courts will confront will be this: What other kinds of records are sufficiently similar to letters in the mail that the same rule should apply?
It may be that, as an original matter, a subpoena requiring the recipient to produce records wasn’t thought of as a “search or seizure” by the government implicating the Fourth Amendment, see ante, at ___ - ___, 201 L. Ed. 2d, at 555-561 (opinion of Alito, J.), but instead as an act of compelled self-incrimination implicating the Fifth Amendment, see United States v. Hubbell, 530 U. S. 27, 49-55, 120 S. Ct. 2037, 147 L. Ed. 2d 24 (2000) (Thomas, J., dissenting); Nagareda, Compulsion “To Be a Witness” and the Resurrection [***155] of Boyd, 74 N. Y. U. L. Rev. 1575, 1619, and n. 172 (1999). But the common law of searches and seizures does not appear to have confronted a case where private documents equivalent to a mailed letter were entrusted to a bailee and then subpoenaed. As a result, “[t]he common-law rule regarding subpoenas for documents held by third parties entrusted with information from the target is . . . unknown [**582] and perhaps unknowable.” Dripps, Perspectives on The Fourth Amendment Forty Years Later: Toward the Realization of an Inclusive Regulatory Model, 100 Minn. L. Rev. 1885, 1922 (2016). Given that (perhaps insoluble) uncertainty, I am content to adhere to Jackson and its implications for now.
To be sure, we must be wary of returning to the doctrine of Boyd v. United States, 116 U. S. 616, 6 S. Ct. 524, 29 L. Ed. 746. Boyd invoked the Fourth Amendment to restrict the use of subpoenas even for ordinary business records and, as Justice Alito notes, eventually proved unworkable. See ante, at ___, 201 L. Ed. 2d, at 561 (dissenting opinion); 3 W. LaFave, J. Israel, N. King, & O. Kerr, Criminal Procedure §8.7(a), pp. 185-187 (4th ed. 2015). But if we were to overthrow Jackson too and deny Fourth Amendment protection to any subpoenaed materials, we would do well to reconsider the scope of the Fifth Amendment while we’re at it. Our precedents treat the right against self-incrimination as applicable only to testimony, not [***156] the production of incriminating evidence. See Fisher v. United States, 425 U. S. 391, 401, 96 S. Ct. 1569, 48 L. Ed. 2d 39 (1976). But there is substantial evidence that the privilege against self-incrimination was also originally understood to protect a person from being forced to turn over potentially incriminating evidence. Nagareda, supra, at 1605-1623; Rex v. Purnell, 96 Eng. Rep. 20 (K. B. 1748); Slobogin, Privacy at Risk 145 (2007).
[*2272] *
What does all this mean for the case before us? To start, I cannot fault the Sixth Circuit for holding that Smith and Miller extinguish any Katz-based Fourth Amendment interest in third party cell-site data. That is the plain effect of their categorical holdings. Nor can I fault the Court today for its implicit but unmistakable conclusion that the rationale of Smith and Miller is wrong; indeed, I agree with that. The Sixth Circuit was powerless to say so, but this Court can and should. At the same time, I do not agree with the Court’s decision today to keep Smith and Miller on life support and supplement them with a new and multilayered inquiry that seems to be only Katz-squared. Returning there, I worry, promises more trouble than help. Instead, I would look to a more traditional Fourth Amendment approach. Even if Katz may still supply one way to prove a Fourth Amendment interest, it has never been the only way. Neglecting more traditional approaches [***157] may mean failing to vindicate the full protections of the Fourth Amendment.
Our case offers a cautionary example. It seems to me entirely possible a person’s cell-site data could qualify as his papers or effects under existing law. Yes, the telephone carrier holds the information. But 47 U. S. C. §222 designates a customer’s cell-site location information as “customer proprietary network information” (CPNI), §222(h)(1)(A), and gives customers certain rights to control use of and access to CPNI about themselves. The statute generally forbids a carrier to “use, disclose, or permit access to individually identifiable” CPNI without the customer’s consent, except as needed to provide the customer’s telecommunications services. §222(c)(1). It also requires the carrier to disclose CPNI “upon affirmative written request by the customer, to [**583] any person designated by the customer.” §222(c)(2). Congress even afforded customers a private cause of action for damages against carriers who violate the Act’s terms. §207. Plainly, customers have substantial legal interests in this information, including at least some right to include, exclude, and control its use. Those interests might even rise to the level of a property right.
The problem is that we do not know anything [***158] more. Before the district court and court of appeals, Mr. Carpenter pursued only a Katz “reasonable expectations” argument. He did not invoke the law of property or any analogies to the common law, either there or in his petition for certiorari. Even in his merits brief before this Court, Mr. Carpenter’s discussion of his positive law rights in cell-site data was cursory. He offered no analysis, for example, of what rights state law might provide him in addition to those supplied by §222. In these circumstances, I cannot help but conclude—reluctantly—that Mr. Carpenter forfeited perhaps his most promising line of argument.
Unfortunately, too, this case marks the second time this Term that individuals have forfeited Fourth Amendment arguments based on positive law by failing to preserve them. See Byrd, 584 U. S., at ___, 138 S. Ct. 1518, 200 L. Ed. 2d 805, 814. Litigants have had fair notice since at least United States v. Jones, 565 U.S. 400, 132 S. Ct. 945, 181 L. Ed. 2d 911 (2012) and Florida v. Jardines, 569 U.S. 1, 133 S. Ct. 1409, 185 L. Ed. 2d 495 (2013) that arguments like these may vindicate Fourth Amendment interests even where Katz arguments do not. Yet the arguments have gone unmade, leaving courts to the usual Katz handwaving. These omissions do not serve the development of a sound or fully protective Fourth Amendment jurisprudence.
1 [omitted]
2 Justice Kennedy argues that this case is in a different category from Jones and the dragnet-type practices posited in Knotts because the disclosure of the cell-site records was subject to “judicial authorization.” Post, at ___ - ___, 201 L. Ed. 2d, at 536-537. That line of argument conflates the threshold question whether a “search” has occurred with the separate matter of whether the search was reasonable. The subpoena process set forth in the Stored Communications Act does not determine a target’s expectation of privacy. And in any event, neither Jones nor Knotts purported to resolve the question of what authorization may be required to conduct such electronic surveillance techniques. But see Jones, 565 U. S., at 430, 132 S. Ct. 945, 181 L. Ed. 2d 911 (Alito, J., concurring in judgment) (indicating that longer term GPS tracking may require a warrant).
3 The parties suggest as an alternative to their primary submissions that the acquisition of CSLI becomes a search only if it extends beyond a limited period. See Reply Brief 12 (proposing a 24-hour cutoff); Brief for United States 55-56 (suggesting a seven-day cutoff). As part of its argument, the Government treats the seven days of CSLI requested from Sprint as the pertinent period, even though Sprint produced only two days of records. Brief for United States 56. Contrary to Justice Kennedy’s assertion, post, at ___, 201 L. Ed. 2d, at 539, we need not decide whether there is a limited period for which the Government may obtain an individual’s historical CSLI free from Fourth Amendment scrutiny, and if so, how long that period might be. It is sufficient for our purposes today to hold that accessing seven days of CSLI constitutes a Fourth Amendment search.
4 Justice Gorsuch faults us for not promulgating a complete code addressing the manifold situations that may be presented by this new technology—under a constitutional provision turning on what is “reasonable,” no less. Post, at ___ - ___, 201 L. Ed. 2d, at 576-577. Like Justice Gorsuch, we “do not begin to claim all the answers today,” post, at ___, 201 L. Ed. 2d, at 578, and therefore decide no more than the case before us.
5 [omitted]