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Cell Phones and Fourth Amendment

Cell Phones and Fourth Amendment protected by Supreme Court

CARPENTER v. UNITED STATES

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

No. 16–402.  Argued November 29, 2017—Decided June 22, 2018 Cell phones perform their wide and growing variety of functions by con-

tinuously 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 carri- ers collect and store this information for their own business purposes. Here, after the FBI identified the cell phone numbers of several rob- bery 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 Amend- ment. 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. Carpen- ter was convicted. The Sixth Circuit affirmed, holding that Carpen- ter lacked a reasonable expectation of privacy in the location infor- mation 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. 4–18.
    • The Fourth Amendment protects not only property interests but certain expectations of privacy as well. Katz United States, 389
  1. S. 347, 351. Thus, when an individual “seeks to preserve some- thing 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 sup- ported by probable cause. Smith v. Maryland, 442 U. S. 735, 740 (in- ternal quotation marks and alterations omitted). The analysis re- garding which expectations of privacy are entitled to protection is informed by historical understandings “of what was deemed an un- reasonable search and seizure when [the Fourth Amendment] was adopted.” Carroll v. United States, 267 U. S. 132, 149. These Found- ing-era understandings continue to inform this Court when applying the Fourth Amendment to innovations in surveillance tools. See, e.g., Kyllo v. United States, 533 U. S. 27.  Pp. 4–7.

  • The digital data at issue—personal location information maintained by a third party—does not fit neatly under existing prec- edents but lies at the intersection of two lines of cases. One set ad- dresses a person’s expectation of privacy in his physical location and movements. See, g., United States v. Jones, 565 U. S. 400 (five Jus- tices concluding that privacy concerns would be raised by GPS track- ing). The other addresses a person’s expectation of privacy in infor- mation 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 compa- ny). Pp. 7–10.
  • 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 loca- tion to his wireless carrier implicates the third-party principle of Smith and Given the unique nature of cell-site records, this Court declines to extend Smith and Miller to cover them. Pp. 10–18.
    • A majority of the Court has already recognized that indi- viduals have a reasonable expectation of privacy in the whole of their physical movements. Allowing government access to cell-site rec- ords—which “hold for many Americans the ‘privacies of life,’ ” Riley 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 poli- cies of most wireless carriers. The Government contends that CSLI data is less precise than GPS information, but it thought the data ac- curate enough here to highlight it during closing argument in Car- penter’s trial. At any rate, the rule the Court adopts “must take ac- count of more sophisticated systems that are already in use or in

 

 

Syllabus

development,” Kyllo, 533 U. S., at 36, and the accuracy of CSLI is rapidly approaching GPS-level precision.  Pp. 12–15.

  • 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 wire- less 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

The third-party doctrine partly stems from the notion that an indi- vidual 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 partic- ular documents sought” and limitations on any “legitimate ‘expecta- tion 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 lo- cation information is not truly “shared” as the term is normally un- derstood. First, cell phones and the services they provide are “such a pervasive and insistent part of daily life” that carrying one is indis- pensable 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.

  • 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 rec- ords that might incidentally reveal location information; and does not consider other collection techniques involving foreign affairs or na- tional security. 17–18.
  1. The Government did not obtain a warrant supported by proba- ble cause before acquiring Carpenter’s cell-site records. It acquired those records pursuant to a court order under the Stored Communi- cations 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. Consequent- ly, 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 le- gitimate 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 GINS- 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.

NOTICE: This opinion is subject to formal revision before publication in the preliminary print of the United States Reports. Readers are requested to notify the Reporter of Decisions, Supreme Court of the United States, Wash- ington, D. C. 20543, of any typographical or other formal errors, in order  that corrections may be made before the preliminary print goes to press.

Video of a 4th Amendment violation in action

No. 16–402
SUPREME COURT OF THE UNITED STATES

UNITED STATESTIMOTHY IVORY CARPENTER, PETITIONER v.

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

[June 22, 2018]

CHIEF JUSTICE ROBERTS delivered the opinion of the Court.

This case presents the question whether the Govern- ment 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 func- tions 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 look- ing 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 infor- mation from the transmission of text messages and rou- tine 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 addi- tional 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

  1. 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 Govern- ment obtained 12,898 location points cataloging Carpen- ter’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

  1. 3d 880 (2016). The court held that Carpenter lacked a reasonable expectation of privacy in the location infor- mation 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 recog- nized, “is to safeguard the privacy and security of individ- uals against arbitrary invasions by governmental offi- cials.” 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 rummage through homes in an unrestrained search for evi- dence 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) (quot-  ing 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 physi- cally 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 quali- fies as a search and requires a warrant supported by probable cause. Smith, 442 U. S., at 740 (internal quota- tion marks and alterations omitted).

Although no single rubric definitively resolves which expectations  of  privacy  are  entitled  to  protection,1    the

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1 JUSTICE KENNEDY believes that there is such a rubric—the “proper- ty-based concepts” that Katz purported to move beyond. Post, at 3 (dissenting opinion). But while property rights are often informative, our cases by no means suggest that such an interest is “fundamental”  or “dispositive” in determining which expectations of privacy are legitimate. Post, at 8–9. JUSTICE THOMAS (and to a  large  extent JUSTICE  GORSUCH)  would  have  us  abandon  Katz  and  return  to   an 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 under- standings 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

  1. 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
  2. Because any other conclusion would leave homeown- ers “at the mercy of advancing technology,” we determined that the Government—absent a warrant—could not capi- talize on such new sense-enhancing technology to explore

——————

exclusively property-based approach. Post, at 1–2, 17–21 (THOMAS J., dissenting); post, at 6–9 (GORSUCH, J., dissenting). Katz of course “discredited” the “premise that property interests control,” 389 U. S., at 353, and we have repeatedly emphasized that privacy interests do not rise or fall with property  rights, see, e.g., United States v.  Jones,    565

  1. S. 400, 411 (2012) (refusing to “make trespass the exclusive test”); Kyllo v. United States, 533 U. S. 27, 32 (2001) (“We have since decou- pled violation of a person’s Fourth Amendment rights from trespassory violation of his property.”). Neither party has asked the Court to reconsider Katz in this case.

 

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 acquisi- tion 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 pur- chased 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 distin- guish 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. Signifi- cantly, 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 sophis- ticated 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 de- vice on Jones’s vehicle and remotely monitored the vehi- cle’s movements for 28 days. The Court decided the case based on the Government’s physical trespass of the vehi- cle. 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 per- son has no legitimate expectation of privacy in information he  voluntarily  turns  over  to  third  parties.”   Smith, 442

  1. S., at 743–744. That remains true “even if the infor- mation is revealed on the assumption that it will be used only for a limited purpose.” United States v. Miller,   425
  2. 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 docu- ments; they were “business records of the banks.”   Id.,   at

  1. 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

——————

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 14–16. 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 (ALITO, J., concurring in judgment) (indicating that longer term GPS tracking may require a warrant).

[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 in- formation [would] be conveyed by that person to the Gov- ernment.”  Id., at 443.

Three years later, Smith applied the same principles in the context of information conveyed to a telephone com- pany. The Court ruled that the Government’s use of a pen register—a device that recorded the outgoing phone num- bers 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

  1. 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 con- veyed” the dialed numbers to the phone company by “ex- pos[ing] 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 “as- sumed 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 effort- lessly compiled.

 

At the same time, the fact that the individual continu- ously 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 ob- tained from Carpenter’s wireless carriers was the product of a search.3

 

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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 19, 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.

 

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 moni- tor 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 contra- venes that expectation. Although such records are gener- ated 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, reli- gious, 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 thor- oughfares 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% admit- ting 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 per- son’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 infor- mation 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 con- straints of the Fourth Amendment.  Only the few with-  out cell phones could escape this tireless and absolute surveillance.

The Government and JUSTICE KENNEDY contend, how- ever, 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 combi- nation 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 argu- ment of his trial.  App. 131.

At any rate, the rule the Court adopts “must take ac- count 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 ap- proaching 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 addi- tion, 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  reason-  able 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 typi- cal 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 ad- dressed 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 cate- gory 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 ‘expec- tation of privacy’ concerning their contents.”   Miller,    425

  1. 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 confi- dential 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 individ- ual 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 per- vasive 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 move- ment 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 gener- ates CSLI, including incoming calls, texts, or e-mails and countless other data connections that a phone automati- cally 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 ob- tained the information from a third party does not over- come 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 Air- lines, 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 evi- dence 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

——————

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 “rea- sonable,” no less. Post, at 10–12. Like JUSTICE GORSUCH, we “do not begin to claim all the answers today,” post, at 13, and therefore decide no more than the case before us.

 

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 “gigan- tic” departure from the probable cause rule, as the Gov- ernment 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 “construc- tive 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 doc- trine—subjecting subpoenas to lenient scrutiny without regard to the suspect’s expectation of privacy in the rec- ords.  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, contem- plated  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 arbi- trary government power much more directly than corpo- rate tax or payroll ledgers. When confronting new con- cerns 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 categori- cal limitation on Fourth Amendment protection, no type of record would ever be protected by the warrant require- ment. Under JUSTICE ALITO’s view, private letters, digital contents of a cell phone—any personal information re- duced  to  document  form,  in  fact—may  be  collected   by

——————

5 See United States v. Dionisio, 410 U. S. 1, 14 (1973) (“No person can have a reasonable expectation that others will not know the sound of  his voice”); Donovan v. Lone Steer, Inc., 464 U. S. 408, 411, 415 (1984) (payroll  and  sales  records);  California  Bankers  Assn.  v.  Shultz, 416

  1. S. 21, 67 (1974) (Bank Secrecy Act reporting requirements); See v. Seattle, 387 U. S. 541, 544 (1967) (financial books and records); United States v. Powell, 379 U. S. 48, 49, 57 (1964) (corporate tax records); McPhaul v. United States, 364 U. S. 372, 374, 382 (1960) (books and records of an organization); United States v. Morton Salt Co., 338 U. S. 632, 634, 651–653 (1950) (Federal Trade Commission reporting re- quirement); Oklahoma Press Publishing Co. v. Walling, 327 U. S. 186, 189, 204–208 (1946) (payroll records); Hale v. Henkel, 201 U. S. 43, 45, 75 (1906) (corporate books and papers).

 

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 Gov- ernment obtains the modern-day equivalents of an indi- vidual’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 doc- trine does not apply to the “modern-day equivalents of an individual’s own ‘papers’ or ‘effects,’ ” then the clear impli- cation is that the documents should receive full Fourth Amendment protection. We simply think that such pro- tection 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 proba- ble cause. The Government will be able to use subpoenas  to acquire records in the overwhelming majority of inves- tigations. We hold only that a warrant is required in the rare case where the suspect has a legitimate privacy in- terest 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 compel- ling that [a] warrantless search is objectively reasonable under  the  Fourth  Amendment.’”   Kentucky  v.  King, 563

  1. 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, 277 U. S. 438, 473–474 (1928). Here the progress of science has afforded law enforcement a power- ful 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 infor- mation.  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 protec- tion. 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.

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