Global Freedom of Expression

Carpenter v. United States

Closed Expands Expression

Key Details

  • Mode of Expression
    Electronic / Internet-based Communication
  • Date of Decision
    June 22, 2018
  • Outcome
    Law or Action Overturned or Deemed Unconstitutional
  • Case Number
    No. 16-402
  • Region & Country
    United States, North America
  • Judicial Body
    Supreme (court of final appeal)
  • Type of Law
    Criminal Law, Constitutional Law, Law of Evidence
  • Themes
    Cyber Security / Cyber Crime, Privacy, Data Protection and Retention, Surveillance
  • Tags
    Internet, Internet Service Providers, Data Protection and Retention, Search Warrant, Personal Information, Personal Data, Protection of personal data, Law enforcement, Admissibility

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Case Analysis

Case Summary and Outcome

The United States Supreme Court held that obtaining cellular location data constitutes a search under the Fourth Amendment of the U.S. Constitution, and thus requires a warrant supported by probable cause. An individual, suspected of being involved in a series of store robberies, sought an order that his rights under the Fourth Amendment, which prohibits unreasonable searches, had been violated when law enforcement obtained records of his cellular location data for the time periods during which the robberies took place. In a 5-4 decision, the Court expressed concern that cellphone records can provide “near perfect surveillance” and that the data is retained for many years and for all users, and held that an individual does have a “reasonable expectation of privacy” in respect of their cellphone location information. Accordingly, the Court ruled that the accessing of the individual’s cellphone location data was an unconstitutional search and therefore a violation of the Fourth Amendment.


In 2011, police officers arrested four men in connection with a series of robberies at RadioShack and T-Mobile stores in Michigan and Ohio, USA. One of these men provided a confession which included the cellphone numbers of some of his accomplices which the federal prosecutors then used in applying for cell records under the Stored Communications Act, 1994. This legislation allows the government to compel certain telecommunications records upon “specific and articulable facts showing there are reasonable grounds to believe … [the records] are relevant and material to an ongoing criminal investigation” [p. 3]. Timothy Carpenter was one of the individuals whose number had been provided to law enforcement and whose records were obtained as a result.

The material sought by prosecutors was “cell-site location information” or CSLI. CSLI is created when cell phones, which continually search for and interact with radio antennas (called cell sites) connect with a site closest to the phone and the relevant network creates time-stamped records of those connections. Cellphone networks store and maintain CSLI for their own purposes, such as identifying network flaws and sharing aggregated location information with data brokers. As modern smart phones connect to networks several times per minute even when not active these phones and urban networks can generate CSLI that exhaustively and accurately catalog a cell phone user’s movements.

On application from the prosecutors, federal magistrate judges issued orders compelling Carpenter’s wireless carriers to produce CSLI for Carpenter’s cellphone “at call origination and at call termination for incoming and outgoing calls” during the four-month period when the string of robberies occurred” [p. 3]. The prosecutors received information detailing 12,898 location points or an average of 101 location points on Carpenter’s movements per day and, partly as a result of this information, charged Carpenter with six counts of robbery and six counts of “carrying a firearm during a federal crime of violence in federal district court”. Carpenter was convicted on all but one of the firearm counts and sentenced to 100 years in prison. Carpenter appealed his conviction, arguing that the use of the CSLI evidence violated the Fourth Amendment of the U.C. Constitution which protects “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.” The Court of Appeals for the Sixth Circuit dismissed his appeal, 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” [p. 4]. The Court found that Carpenter was not entitled to the protection of the Fourth Amendment because cellphone users “voluntarily convey cell-site data to their carriers as ‘a means of establishing communication’” [p. 4].

Carpenter then appealed to the U.S. Supreme Court.

Decision Overview

The Chief Justice Roberts, joined by Justices Ginsburg, Breyer, Sotomayor and Kagan, delivered the opinion of the Court. The central issue for the Court to determine was whether obtaining cellphone location records constituted a “search” for the purposes of the Fourth Amendment, and whether, if so, that search had been constitutional.

With reference to the case of Camara v. Municipal Court of City and County of San Francisco, 387 U. S. 523, 528 (1967), the Court noted that the basic purpose of the Fourth Amendment “is to safeguard the privacy and security of individuals against arbitrary invasions by governmental officials.” It added that “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” [p. 5].

The Court stated that its jurisprudence had established two “basic guideposts”: in Boyd v. United States, 116 U. S. 616, 630 (1886) that the Fourth Amendment “seeks to secure ‘the privacies of life’ against ‘arbitrary power’;” and in United States v. Di Re, 332 U. S. 581, 595 (1948) that “a central aim of the Framers was ‘to place obstacles in the way of a too permeating police surveillance’.” [p. 6]. The Court stressed that it has used these principles in interpreting the Fourth Amendment in respect of developing surveillance technology.

The Court recognized that the present case – with its focus on “digital data – personal location information maintained by a third party” – did “not fit neatly under existing precedents” [p. 7] but noted that there were two broad themes in its jurisprudence which could be applied to the present case. The first set of cases “addresses a person’s expectation of privacy in his physical location and movements” [p. 7]. In United States v. Knotts, 460 U. S. 276 (1983) the Court had held that the use by law enforcement of a “beeper” to track a suspect’s car did not constitute a “search” for the purposes of the Fourth Amendment because an individual driving a car on public roads had no reasonable expectation of privacy [p. 8]. However, in the Knotts case the Court had noted that the precedent may not be applicable to more invasive forms of surveillance. In United States v. Jones 565 U. S. 400, 405 (2012) the Court did assess the constitutionality of greater forms of surveillance, holding that by placing a GPS device in a suspect’s car, the FBI was able to monitor every movement of that individual which was an infringement of his privacy.

The second set of cases involved the Court “draw[ing] a line between what a person keeps to himself and what he shares with others” and stressing that “a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties” [p. 9]. The Court referred to the cases of United States v. Miller 425 U. S. 435, 443 (1976) and Smith v. Maryland 442 U. S. 735, 745 (1979) which had held that by using bank checks and placing telephone calls respectively the individuals in these cases had assumed the risk that the information would be provided to police [p. 10].

In applying these two strands of cases to the present case, the Court recognized the difficulty in reconciling the two competing doctrines in Fourth Amendment cases: one protecting privacy in one’s physical location and movements, and another finding a reduced expectation of privacy in information shared with third parties. The Court held that the principles established in the Miller and Smith cases could not be extended to the use of CSLI information, and that, “an individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through CSLI” [p. 12]. Accordingly, the Court held that the “location information obtained from Carpenter’s wireless carriers was the product of a search” [p. 12].

The Court noted that “[a] person does not surrender all Fourth Amendment protection by venturing into the public sphere” [p. 12]. It noted that, in the past, it would have been physically impossible for law enforcement to monitor an individual indefinitely, and that there was therefore no expectation that an individual would be subjected to such surveillance. The Court commented that “[a]llowing government access to cell-site records contravenes that expectation” [p. 12]. The Court highlighted the privacy concerns inherent in CSIL data access. It Court noted that tracking cellphone positioning using CSIL “present even greater privacy concerns” than tracking a vehicle using GPS because individuals keep their cellphones on them almost constantly and so “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” [p. 13]. The Court also commented on the retroactive nature of the CSIL data, and that “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” [p. 13]. In addition, the CSIL data is retained by the networks for all users which meant that “this newfound tracking capacity runs against everyone” and not just those under official investigation [p. 13].

In rejecting the government’s argument that the third-party principle from the Miller case applied to the present case, the Court noted that the government 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” [p. 15]. It commented that “[t]he 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” [p. 15].

The Court also distinguished the present case from the situation in the Miller case as “[c]ell phone location information is not truly ‘shared’ as one normally understands the term” [p. 17]. The Court commented that because there is no way – save disconnecting from the network – to not provide the information, unlike in Miller, in this case “in no meaningful sense does the user voluntarily ‘assume[] the risk’ of turning over a comprehensive dossier of his physical movements” [p. 17]

The Court stated that because of its finding that obtaining CSIL records constitutes a search under the Fourth Amendment, law enforcement is required to obtain a warrant supported by probable cause in order to access these records [p. 18]. It did recognize that there may be some rare exceptions, for example, “if law enforcement is confronted with an urgent situation, such fact-specific threats will likely justify the warrantless collection of CSLI” [p. 22].  As the Stored Communications Act merely requires the government to show “reasonable grounds” for believing that the CSIL data were relevant to an investigation, the Court held that this fell short of the standard required by “probable cause” and the search was therefore unconstitutional.

In closing, the Court held that “[i]n 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” and that as “[t]he Government’s acquisition of the cell-site records here was a search under that Amendment” it “decline[d] to grant the state unrestricted access to a wireless carrier’s database of physical location information” [p. 22].

Justice Kennedy delivered a dissenting opinion, joined by Justices Thomas and Alito, which expressed concern that the Supreme Court was departing from Fourth Amendment precedent, which should have guided the Court to find that there was no violation of the Fourth Amendment. This dissenting judgment noted that there should be no difference between CSIL data and other business records that – following the Miller case – law enforcement is entitled to obtain from a suspect without implicating the Fourth Amendment. It added that it would have found that Carpenter had no reasonable expectation of privacy in respect of his CSIL records and noted that a “person’s movements are not particularly private” [p. 17].

Justice Thomas delivered a dissenting opinion which stated that the CSIL records were the property of the networks, and so the Fourth Amendment did not apply because the “search” did not occur in respect of Carpenter’s own property. This judgment also called for a reassessment of the “reasonable expectation of privacy” test established in the Katz case and the application of that test to the concept of “search” in the Fourth Amendment. It added that the Katz case had impermissibly shifted the focus of the Fourth Amendment from property to privacy.

Justice Alito delivered a dissenting opinion, joined by Justice Thomas, which stated that the order under the Stored Communications Act was not a search of Carpenter’s private records but only a request for a third party to look through theirs. It added that treating the obtaining of CSIL records as a search is “revolutionary” as it “violates both the original understanding of the Fourth Amendment and more than a century of Supreme Court precedent” [p. 1].

Justice Gorsuch delivered a dissenting opinion which called for a rejection of the Katz and Miller and Smith decisions and adoption of a new approach.

Decision Direction

Quick Info

Decision Direction indicates whether the decision expands or contracts expression based on an analysis of the case.

Expands Expression

This judgment expands protections for privacy in the digital age and limits the capacity of law enforcement to utilize detailed cellphone location information in surveillance activities. It departs from previous applications of the Fourth Amendment by extending protection to records held by third parties that reveal extensive personal data on their private life or personal location information.

Global Perspective

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Global Perspective demonstrates how the court’s decision was influenced by standards from one or many regions.

Table of Authorities

National standards, law or jurisprudence

Case Significance

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Case significance refers to how influential the case is and how its significance changes over time.

The decision establishes a binding or persuasive precedent within its jurisdiction.

Decision (including concurring or dissenting opinions) establishes influential or persuasive precedent outside its jurisdiction.

The decision was cited in:

Official Case Documents

Official Case Documents:

Amicus Briefs and Other Legal Authorities

  • Brief of Amici Curiae Electronic Frontier Foundation, Brennan Center For Justice, The Constitution Project, National Association of Criminal Defense Lawyers and National Association of Federal Defenders In Support of Petitioner

  • Reports, Analysis, and News Articles:


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