Whether the warrantless seizure and search of historical cell phone records revealing the location and movements of a cell phone user over the course of 127 days is permitted by the Fourth Amendment.


The Fourth Amendment to the U.S. Constitution provides:

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

The Stored Communications Act, 18 U.S.C. 2703, provides in relevant part: (c) Records concerning electronic communication service or remote computing service.--(1) A govern­mental entity may require a provider of electronic communication service or remote computing service to disclose a record or other information pertaining to a subscriber to or customer of such service (not including the contents of communications) only when the governmental entity--

(A) obtains a warrant issued using the procedures described in the Federal Rules of Criminal Procedure (or, in the case of a State court, issued using State warrant procedures) by a court of competent jurisdiction; [or]

(B) obtains a court order for such disclosure under subsection (d) of this section; * * *

(d) Requirements for court order.-­A court order for disclosure may be issued by any court that is a court of competent jurisdiction and shall issue only if the governmental entity offers specific and articulable facts showing that there are reasonable grounds to believe that the contents of a wire or electronic communication, or the records or other information sought, are relevant and material to an ongoing criminal investigation



1. This case concerns governmental acquisition of personal location records, known as cell site location information ("CSLI"), to identify Petitioner Timothy Carpenter's whereabouts over more than four months. The records, which are logged and retained by cellular service providers whenever people carry modern cell phones, make it possible to reconstruct in detail everywhere an individual has traveled over hours, days, weeks, or months.

In order to access the cellular network, cell phones must connect to nearby cell towers (known as "cell sites"), thereby creating a record of the phone's location. The precision of a cell phone user's location reflected in CSLI records depends on the size of the cell site "sectors" in the area. Most cell sites consist of multiple directional antennas that divide the cell site into sectors. The majority of cell sites comprise three directional antennas that divide the cell site into three sectors (usually 120 degrees each), but an increasing number of towers have six antennas (covering approximately 60 degrees each). The coverage area of each cell site sector is smaller in areas with greater density of cell sites, with urban areas having the greatest density and thus the smallest coverage areas. The smaller the coverage area, the more precise the location information revealed and recorded.

The density of cell sites continues to increase as data usage from smartphones grows. Because each cell site carries a fixed volume of data required for text messages, emails, web browsing, streaming video, and other uses, as smartphone data usage increases, carriers erect additional cell sites, each covering smaller geographic areas. This means that in urban and dense suburban areas like Detroit, many sectors cover small geographic areas.

Service providers have long retained location information for the start and end of incoming and outgoing calls. Today, those companies increasingly also retain location information related to the transmission of text messages and routine internet connections-which smartphones make virtually constantly to check for new emails, social media messages, weather updates, and other functions. The information recorded can include not only cell site and sector, but also estimated distance of the phone from the nearest cell site. Location precision is also increasing as service providers deploy millions of "small cells," which cover a very specific area, such as one floor of a building, the waiting room of an office, or a single home.

All told, a typical smartphone connects to cell towers hundreds of times a day, generating a densely pixelated matrix of data points documenting the user's movements. The volume and precision of that data will grow steadily in coming years, generating ever more granular locational information.

Congress has explicitly recognized the sensitivity of CSLI. The Telecommunications Act treats this data as proprietary to the customer, and bars cellular service providers from sharing a customer's CSLI without the customer's express advance approval.

2. In 2011, officers from the Detroit Police Department arrested four individuals they thought had robbed Radio Shack and T-Mobile stores in Detroit, Michigan. One of the arrestees admitted he had a role in eight different robberies that started in December of 2010 and lasted through March of 2011 at Radio Shack and T-­Mobile stores in Michigan and Ohio. The [arrestee] identified 15 other individuals who had been involved in at least one of the eight robberies.

An Assistant United States Attorney then submitted three applications for orders to access 152 days of historical cell phone location records for Timothy Carpenter and several other suspects. The applications, which were unsworn, did not seek warrants based on probable cause, but rather orders under a 1986 law, the Stored Communications Act ("SCA"). SCA orders may issue when the government 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.

The primary application at issue here asserted that "the requested records will assist in identifying and locating the other individuals believed to be involved in the armed robberies" and "provide evidence that Timothy Carpenter and other known and unknown individuals are violating provisions of Title 18, United States Code, 1951. The application sought "[a]ll subscriber information, toll records and call detail records . . . from [the] target telephones from December 1, 2010 to present[,]" as well as "cell site information for the target telephones at call origination and at call termination for incoming and outgoing calls[.]"

Magistrate judges issued two separate orders granting the applications for Carpenter's records. A third order, also granted, sought CSLI of other suspects. The first order directed MetroPCS, Carpenter's cellular service provider, to "provide the locations of celllsite sector (physical addresses) for the target telephones at call origination and at call termination for incoming and outgoing calls" from "December 1, 2010 to present [May 2, 2011]." MetroPCS complied, providing 186 pages of Carpenter's cell phone records (known as "call detail records") to the government. Those records show the cell site and sector that Carpenter's phone connected to at the start and end of most of his incoming and outgoing calls over the course of 127 days.

The second order directed Sprint to produce cell site location information for Carpenter's phone while it was "roaming on Sprint's cellular tower network" for seven days in March, 2011. Metro PCS does not have coverage in the Warren, Ohio area, where one of the charged robberies took place, and has a roaming agreement with Sprint, which does cover that area." Therefore, Sprint, not MetroPCS, possessed Carpenter's CSLI for his time spent in and around Warren. Sprint produced two days' worth of CSLI.

MetroPCS and Sprint also produced lists of their cell sites in southern Michigan and northwestern Ohio, respectively, providing the longitude, latitude, and physical address of each cell site, along with the directional orientation of each sector antenna. Cross-referencing the information in Carpenter's call detail records with these cell site lists allowed law enforcement to identify the area in which Carpenter's phone was located and thereby to deduce Carpenter's location and movements over the course of each day.

All told, the government obtained 12,898 CSLI data points tracing Carpenter's movements-an average of 101 location points per day for more than four months' time.

3. Before trial, Carpenter moved to suppress the CSLI records on the basis that the Fourth Amendment prohibits their acquisition without probable cause and a warrant. The district court denied the motion, reasoning that people do not have a reasonable expectation of privacy in CSLI records and, consequently, their acquisition by the government does not constitute a "search" under the Fourth Amendment.

At trial, FBI Special Agent Christopher Hess testified that Carpenter's CSLI placed him near four of the charged robberies. Hess produced maps, constructed using the CSLI, which showed the location of Carpenter's phone relative to the locations of the robberies. The government relied on the records to show Carpenter's proximity to "the robberies around the time the robberies happened." The prosecutor argued to the jury, for example, that Carpenter was "right where the first robbery was at the exact time of the robbery, the exact sector," and that he was "right in the right sector before the RadioShack [robbery] in Highland Park."


The jury convicted Carpenter of six robberies in violation of the Hobbs Act, 18 U.S.C. 1951(a), and five separate violations of 18 U.S.C. 924(c) for using or carrying a firearm in connection with a federal crime of violence and aiding and abetting the commission of that offense. The court sentenced Carpenter to nearly 116 years' imprisonment.

4. A divided panel of the Sixth Circuit affirmed. The panel majority acknowledged that in United States v. Jones (2012), five Justices agreed that people have a reasonable expectation of privacy in information very similar to the CSLI data obtained here-namely, "longer term GPS monitoring in government investigations of most offenses." But the majority held that individuals have no reasonable expectation of privacy in cell phone location records. It distinguished Jones on the ground that "[t]his case involves business records obtained from a third-party," which the majority viewed as more like the landline calling records that this Court held in 1979 were not entitled to Fourth Amendment protection. The majority also noted that the GPS information in Jones was "accurate enough to show that the target [was] located within an individual building," while CSLI was less precise.


I. Under this Court's recent Fourth Amendment cases, the government conducted a search when it obtained 127 days of petitioner's cell phone location records from his cellular service provider.

A. When the government employs new technology to obtain sensitive personal information in a way that diminishes the degree of privacy that individuals reasonably expected prior to the technology's adoption, it conducts a search under the Fourth Amendment. Applying this principle in United States v. Jones, five Justices concluded that longer-term GPS tracking of a car violates reasonable expectations of privacy. Tracing a person's geographical movements reveals highly sensitive personal information, and prior to the digital age, people reasonably expected that police in most investigations would not have followed a person and recorded her every movement for days or weeks on end.

The same analysis controls this case. CSLI exposes a great volume of highly sensitive information about a person, revealing where she has been and whom she has been with throughout each day. And as acute as that concern is today, it will only sharpen over time, as the volume and precision of CSLI records steadily increases. Furthermore, just as with GPS tracking, the government prior to the widespread proliferation of cell phones could have obtained only very limited information about a person's past geographical movements. Police officers could have, for example, interviewed witnesses, sought security camera footage, or examined store receipts near the scene of a crime. But these tactics pale in comparison to the unprecedented surveillance time machine that CSLI provides.

In addition, obtaining CSLI records invades an individual's Fourth Amendment right to security in his private "papers." Federal law grants individuals a proprietary interest in their CSLI records by prohibiting service providers from disclosing that information without express prior authorization of the customer. Wholly apart from a reasonable-expectation-of-privacy analysis, the government's impingement on that interest for purposes of gathering information constitutes a search.

B. Contrary to the Sixth Circuit's view, decades-old cases involving the "third-party doctrine" do not render the Fourth Amendment inapplicable here. In Smith v. Maryland (1979), and United States v. Miller (1976), this Court concluded that people lack a reasonable expectation of privacy in dialed telephone numbers and banking records, because of the records' limited sensitivity and because the information involved was voluntarily conveyed to third parties. But a great gulf divides those cases from the investigative activity at issue here.

The detailed and pervasive location records obtained in this case are far more comprehensive and sensitive than discrete telephonic or banking information. And location data is not "voluntarily" conveyed by a phone user in the same sense as the information in Smith and Miller. Cell phones are indispensable to participation in modern society ­often required for employment, relied on for personal safety, and increasingly becoming essential medical treatment tools. Even if it could be said that possessing a cell phone is a voluntary act, it certainly cannot be said that cell phone owners knowingly and intentionally disclose their minute-by-minute movements in historical perpetuity. Carrying a smartphone, checking for new emails from one's boss, updating the weather forecast, and downloading directions ought not license total surveillance of a person's entire life.

As this Court's decisions in Jones, and Riley v. California (2014), illustrate, the innovations of the digital age preclude wooden extension of analog-era precedents where technology has greatly increased the government's ability to obtain intimate information. Extending Smith and Miller to CSLI would lead to unacceptable consequences. It would mean not only that CSLI is exempt from the Fourth Amendment, but also that persons would lack any reasonable expectation of privacy in the contents of emails and other communications that are necessarily shared with service providers to enable their transmission. People reasonably expect that the details of where they travel over an extended period are known only to themselves, and therefore cannot be obtained by the government without implicating the Fourth Amendment.

II. This Court may wish to allow the Sixth Circuit to determine in the first instance whether a search of CSLI pursuant to an order under the Stored Communications Act is "reasonable" under the Fourth Amendment. Should the Court reach the question, however, it should hold that such a search is unreasonable.

The usual rule is that a warrant is required for criminal investigative searches. And Congress has not decreed here to the contrary. Congress enacted the SCA prior to the widespread proliferation of cell phones and without awareness of the coming availability of CSLI.

Nor does any exception to the warrant requirement apply here. The government argues that its subpoena power allows it to obtain CSLI records on a showing of less than probable cause. But the subpoena power allows the government merely to obtain business records in which businesses have a diminished expectation of privacy, if they have any at all. This Court has never extended that power to records as to which individuals have a reasonable expectation of privacy. And allowing warrantless access to such information-particularly CSLI records-would constitute a massive expansion of government power and a threat to personal privacy akin to the general warrants that the Framers of the Fourth Amendment so abhorred.

In sum, clarifying that a warrant is required will ensure that law enforcement officers can acquire particular spans of location records where there is probable cause that they will provide evidence of criminal conduct. And it will protect records that are not pertinent to the investigation but that can reveal much private information about a person's life. This Court should provide a "simple" answer to the question presented: "get a warrant."


For the foregoing reasons, the judgment of the Sixth Circuit should be reversed.