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Carpenter v. United States

United States Supreme Court

June 22, 2018

TIMOTHY IVORY CARPENTER, PETITIONER
v.
UNITED STATES

          Argued November 29, 2017

          ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR THE SIXTH CIRCUIT

         Syllabus

         Cell phones perform their wide and growing variety of functions by continuously connecting to a set of radio antennas called "cell sites." Each time a phone connects to a cell site, it generates a time-stamped record known as cell-site location information (CSLI). Wireless carriers collect and store this information for their own business purposes. Here, after the FBI identified the cell phone numbers of several robbery suspects, prosecutors were granted court orders to obtain the suspects' cell phone records under the Stored Communications Act. Wireless carriers produced CSLI for petitioner Timothy Carpenter's phone, and the Government was able to obtain 12, 898 location points cataloging Carpenter's movements over 127 days-an average of 101 data points per day. Carpenter moved to suppress the data, arguing that the Government's seizure of the records without obtaining a warrant supported by probable cause violated the Fourth Amendment. The District Court denied the motion, and prosecutors used the records at trial to show that Carpenter's phone was near four of the robbery locations at the time those robberies occurred. Carpenter was convicted. The Sixth Circuit affirmed, holding that Carpenter lacked a reasonable expectation of privacy in the location information collected by the FBI because he had shared that information with his wireless carriers.

         Held:

1. The Government's acquisition of Carpenter's cell-site records was a Fourth Amendment search. Pp. 4-18.
(a) The Fourth Amendment protects not only property interests but certain expectations of privacy as well. Katz v. United States, 389 U.S. 347, 351. Thus, when an individual "seeks to preserve something as private," and his expectation of privacy is "one that society is prepared to recognize as reasonable," official intrusion into that sphere generally qualifies as a search and requires a warrant supported by probable cause. Smith v. Maryland, 442 U.S. 735, 740 (internal quotation marks and alterations omitted). The analysis regarding which expectations of privacy are entitled to protection is informed by historical understandings "of what was deemed an unreasonable search and seizure when [the Fourth Amendment] was adopted." Carroll v. United States, 267 U.S. 132, 149. These Founding-era understandings continue to inform this Court when applying the Fourth Amendment to innovations in surveillance tools. See, e.g., Kyllov. United States, 533 U.S. 27. Pp. 4-7.
(b)The digital data at issue-personal location information maintained by a third party-does not fit neatly under existing precedents but lies at the intersection of two lines of cases. One set addresses a person's expectation of privacy in his physical location and movements. See, e.g., United States v. Jones, 565 U.S. 400 (five Justices concluding that privacy concerns would be raised by GPS tracking). The other addresses a person's expectation of privacy in information voluntarily turned over to third parties. See United States v. Miller, 425 U.S. 435 (no expectation of privacy in financial records held by a bank), and Smith, 442 U.S. 735 (no expectation of privacy in records of dialed telephone numbers conveyed to telephone company). Pp. 7-10.
(c)Tracking a person's past movements through CSLI partakes of many of the qualities of GPS monitoring considered in Jones-it is detailed, encyclopedic, and effortlessly compiled. At the same time, however, the fact that the individual continuously reveals his location to his wireless carrier implicates the third-party principle of Smith and Miller. Given the unique nature of cell-site records, this Court declines to extend Smith and Miller to cover them. Pp. 10-18.
(1) A majority of the Court has already recognized that individuals have a reasonable expectation of privacy in the whole of their physical movements. Allowing government access to cell-site records-which "hold for many Americans the 'privacies of life, '" Riley v. California, 573 U.S. ___, ___ -contravenes that expectation. In fact, historical cell-site records present even greater privacy concerns than the GPS monitoring considered in Jones: They give the Government near perfect surveillance and allow it to travel back in time to retrace a person's whereabouts, subject only to the five-year retention policies of most wireless carriers. The Government contends that CSLI data is less precise than GPS information, but it thought the data accurate enough here to highlight it during closing argument in Carpenter's trial. At any rate, the rule the Court adopts "must take account of more sophisticated systems that are already in use or in development," Kyllo, 533 U.S., at 36, and the accuracy of CSLI is rapidly approaching GPS-level precision. Pp. 12-15.
(2) The Government contends that the third-party doctrine governs this case, because cell-site records, like the records in Smith and Miller, are "business records," created and maintained by wireless carriers. But there is a world of difference between the limited types of personal information addressed in Smith and Miller and the exhaustive chronicle of location information casually collected by wireless carriers.
The third-party doctrine partly stems from the notion that an individual has a reduced expectation of privacy in information knowingly shared with another. Smith and Miller, however, did not rely solely on the act of sharing. They also considered "the nature of the particular documents sought" and limitations on any "legitimate 'expectation of privacy' concerning their contents." Miller, 425 U.S., at 442. In mechanically applying the third-party doctrine to this case the Government fails to appreciate the lack of comparable limitations on the revealing nature of CSLI.
Nor does the second rationale for the third-party doctrine- voluntary exposure-hold up when it comes to CSLI. Cell phone location information is not truly "shared" as the term is normally understood. First, 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 ___. Second, a cell phone logs a cell-site record by dint of its operation, without any affirmative act on the user's part beyond powering up. Pp. 15-17.
(d) This decision is narrow. It does not express a view on matters not before the Court; does not disturb the application of Smith and Miller or call into question conventional surveillance techniques and tools, such as security cameras; does not address other business records that might incidentally reveal location information; and does not consider other collection techniques involving foreign affairs or national security. Pp. 17-18.
2. The Government did not obtain a warrant supported by probable cause before acquiring Carpenter's cell-site records. It acquired those records pursuant to a court order under 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. Consequently, an order issued under §2703(d) is not a permissible mechanism for accessing historical cell-site records. Not all orders compelling the production of documents will require a showing of probable cause. A warrant is required only in the rare case where the suspect has a legitimate privacy interest in records held by a third party. And even though the Government will generally need a warrant to access CSLI, case-specific exceptions-e.g., exigent circumstances-may support a warrantless search. Pp. 18-22.

         819 F.3d 880, reversed and remanded.

          ROBERTS, C. J., delivered the opinion of the Court, in which GlNS-BURG, 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.

          OPINION

          Roberts Chief Justice.

         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.

         I

         A

         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 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, 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 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.

         B

         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 several other suspects. That statute, as amended in 1994, permits the Government to compel the disclosure of certain telecommunications 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 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, 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 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 (1979)).

         We granted certiorari. 582 U.S. ___(2017).

         II

         A

         The Fourth Amendment protects "[t]he right of the people to be secure 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 (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 rum- mage through homes in an unrestrained search for evidence of criminal activity." Riley v. California, 573 U.S. ___, ___ (2014) (slip op., at 27). 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 ___-___ (slip op., at 27-28) (quoting 10 Works of John Adams 248 (C. Adams ed. 1856)).

         For much of our history, Fourth Amendment search doctrine was "tied to common-law 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 (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 (1992). In Katz v. United States, 389 U.S. 347, 351 (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 (internal quotation marks and alterations omitted).

         Although no single rubric definitively resolves which expectations of privacy are entitled to protection, [1] the analysis is informed by historical understandings "of what was deemed an unreasonable search and seizure when [the Fourth Amendment] was adopted." Carroll v. United States, 267 U.S. 132, 149 (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 (1886). Second, and relatedly, that a central aim of the Framers was "to place obstacles in the way of a too permeating police surveillance." United States v. Di Re, 332 U.S. 581, 595 (1948).

         We have kept this attention to Founding-era understandings in mind when applying the Fourth Amendment to innovations in surveillance tools. 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 (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. 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 ___ (slip op., at 17). We explained that while the general rule allowing warrantless 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 ___ (slip op., at 9).

         B

         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 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 (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 signal to help keep the 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. 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.

         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. 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.

         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 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. 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 (ALITO, J., concurring in judgment); id., at 415 (SOTOMAYOR, J., concurring). 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 (opinion of ALITO, J.); id., at 415 (opinion of SOTOMAYOR, J.).[2]

         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 743-744. That remains true "even if the information is revealed on the assumption that it will be used only for a limited purpose." United States v. Miller, 425 U.S. 435, 443 (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. 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. 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.

         Three years later, Smith applied the same principles in the context of information 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. 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. 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 "exposing] that information to its equipment in the ordinary course of business." Id., at 744 (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.

         III

         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 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 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 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. 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 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]

         A

         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. 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 (Alito, J., concurring in judgment); id., at 415 (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 (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.

         Allowing government access to cell-site records contravenes that expectation. Although 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 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 (opinion of SOTOMAYOR, J.). These location records "hold for many Americans the 'privacies of life.'" Riley, 573 U.S., at ___ (slip op., at 28) (quoting Boyd, 116 U.S., at 630). And like GPS monitoring, cell phone 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 ___ (slip op., at 9)-tracks nearly exactly the movements of its owner. 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 ___(slip op., at 19) (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 (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 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 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 18-19. Yet the Court has already rejected the proposition that "inference insulates a search." Kyllo, 533 U.S., at 36. 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." Kyllo, 533 U.S., at 36. 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 from the wireless carriers, it invaded Carpenter's reasonable expectation of privacy in the whole of his physical movements.

         B

         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 12-14.

         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 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.

         The third-party doctrine partly stems from the notion that an individual has a reduced expectation of 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 ___(slip op., at 16). 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. 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; Riley, 573 U.S., at ___ (slip op., at 24). Miller likewise noted that checks were "not confidential communications but negotiable instruments to be used in commercial transactions." 425 U.S., at 442. In mechanically applying the third-party doctrine to this case, the Government fails to appreciate that there are no comparable limitations on the revealing 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 conveyed to anyone who wanted to look." Knotts, 460 U.S., at 281; see id., at 283 (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 (ALITO, J., concurring in judgment); id., at 415 (SOTOMAYOR, J., concurring). JUSTICE GORSUCH wonders why "someone's location when using a phone" is sensitive, post, at 3, and Justice Kennedy assumes that a person's discrete movements "are not particularly private," post, at 17. 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 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 ___(slip op., at 9). 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 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.

         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 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 (1944).[4]

         IV

         Having found that the acquisition of Carpenter's CSLI was a search, we also conclude that 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 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 (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 ___(slip op., at 5).

         The Government acquired the cell-site records pursuant to a court order issued under 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 (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 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 12. 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 8-19.

         But 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 14-15, contemplated requests for evidence implicating diminished pri- vacy interests or for a corporation's own books.[5] The lone exception, of course, is Miller, where the Court's analysis of the third-party subpoena merged with the application of the third-party doctrine. 425 U.S., at 444 (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 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 ___(slip op., at 10) ("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 (1950). Justice Kennedy declines to adopt the radical implications of this theory, 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 13 (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.

         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, even though the Government will generally need a warrant to access CSLI, case-specific exceptions may support 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 (2011) (quoting Mincey v. Arizona, 437 U.S. 385, 394 (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.

         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.

         As Justice Brandeis explained in his famous dissent, the Court is obligated-as "[s]ubtler and more far-reaching means of invading privacy have become available to the Government"-to ensure that the "progress of science" does not erode Fourth Amendment protections. Olmstead v. United States, 211 U.S. 438, 473-474 (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.

         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.

         It is so ordered.

          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 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 (1976); Smith v. Maryland, 442 U.S. 735 (1979). This is true even when the records contain personal and sensitive information. So when the Government uses a subpoena to obtain, for 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.

         In this case petitioner challenges 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.

         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 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. ___, ___-___ (2017) (slip op., at 4-6). 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.

         I

         Before evaluating the question presented it is helpful to understand the nature of cell-site records, how they are commonly used by cell phone service providers, and their proper use by law enforcement.

         When a cell phone user makes a call, sends a text message or e-mail, or gains access to the Internet, the cell phone establishes a radio connection to an antenna at a nearby cell site. The typical cell site covers a more-or-less circular geographic area around the site. It has three (or sometimes six) separate antennas pointing in different directions. Each provides cell service for a different 120-degree (or 60-degree) sector of the cell site's circular coverage area. So a cell phone activated on the north side of a cell site will connect to a different antenna than a cell phone on the south side.

         Cell phone service providers create records each time a cell phone connects to an antenna at a cell site. For a phone call, for example, the provider records the date, time, and duration of the call; the phone numbers making and receiving the call; and, most relevant here, the cell site used to make the call, as well as the specific antenna that made the connection. The cell-site and antenna data points, together with the date and time of connection, are known as cell-site location information, or cell-site records. By linking an individual's cell phone to a particular 120-or 60-degree sector of a cell site's coverage area at a particular time, cell-site records reveal the general location of the cell phone user.

         The location information revealed by cell-site records is imprecise, because an individual cell-site sector usually covers a large geographic area. The FBI agent who offered expert testimony about the cell-site records at issue here testified that a cell site in a city reaches between a half mile and two miles in all directions. That means a 60-degree sector covers between approximately one-eighth and two square miles (and a 120-degree sector twice that area). To put that in perspective, in urban areas cell-site records often would reveal the location of a cell phone user within an area covering between around a dozen and several hundred city blocks. In rural areas cell-site records can be up to 40 times more imprecise. By contrast, a Global Positioning System (GPS) can reveal an individual's location within around 15 feet.

         Major cell phone service providers keep cell-site records for long periods of time. There is no law requiring them to do so. Instead, providers contract with their customers to collect and keep these records because they are valuable to the providers. Among other things, providers aggregate the records and sell them to third parties along with other information gleaned from cell phone usage. This data can be used, for example, to help a department store determine which of various prospective store locations is likely to get more foot traffic from middle-aged women who live in affluent zip codes. The market for cell phone data is now estimated to be in the billions of dollars. See Brief for Technology Experts as Amici Curiae 23.

         Cell-site records also can serve an important investigative function, as the facts of this case demonstrate. Petitioner, Timothy Carpenter, along with a rotating group of accomplices, robbed at least six RadioShack and T-Mobile stores at gunpoint over a 2-year period. Five of those robberies occurred in the Detroit area, each crime at least four miles from the last. The sixth took place in Warren, Ohio, over 200 miles from Detroit.

         The Government, of course, did not know all of these details in 2011 when it began investigating Carpenter. In April of that year police arrested four of Carpenter's coconspirators. One of them confessed to committing nine robberies in Michigan and Ohio between December 2010 and March 2011. He identified 15 accomplices who had participated in at least one of those robberies; named Carpenter as one of the accomplices; and provided Carpenter's cell phone number to the authorities. The suspect also warned that the other members of the conspiracy planned to commit more armed robberies in the immediate future.

         The Government at this point faced a daunting task. Even if it could identify and apprehend the suspects, still it had to link each suspect in this changing criminal gang to specific robberies in order to bring charges and convict. And, of course, it was urgent that the Government take all necessary steps to stop the ongoing and dangerous crime spree.

         Cell-site records were uniquely suited to this task. The geographic dispersion of the robberies meant that, if Carpenter's cell phone were within even a dozen to several hundred city blocks of one or more of the stores when the different robberies occurred, there would be powerful circumstantial evidence of his participation; and this would be especially so if his cell phone usually was not located in the sectors near the stores except during the robbery times.

         To obtain these records, the Government applied to federal magistrate judges for disclosure orders pursuant to §2703(d) of the Stored Communications Act. That Act authorizes a magistrate judge to issue an order requiring disclosure of cell-site records if the Government demonstrates "specific and articulable facts showing that there are reasonable grounds to believe" the records "are relevant and material to an ongoing criminal investigation." 18 U.S.C. §§2703(d), 2711(3). The full statutory provision is set out in the Appendix, infra.

         From Carpenter's primary service provider, MetroPCS, the Government obtained records from between December 2010 and April 2011, based on its understanding that nine robberies had occurred in that timeframe. The Government also requested seven days of cell-site records from Sprint, spanning the time around the robbery in Warren, Ohio. It obtained two days of records.

         These records confirmed that Carpenter's cell phone was in the general vicinity of four of the nine robberies, including the ...


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