Antitrust and Unfair Competition Law

In Seminal Digital Privacy Ruling, U.S. Supreme Court Finds a Fourth Amendment Right of Privacy in Cell-Site Location Information Maintained by Cell Phone Companies

Jonathan Levine
Pritzker Levine LLP

In a victory for digital privacy advocates, on June 22, 2018, the United States Supreme Court held that individuals maintain legitimate expectations of privacy, for Fourth Amendment purposes, in their cell-site location information (CSLI) maintained by cell phone companies and that the government generally may not collect CSLI from cell phone companies without a warrant. Carpenter v. United States, __ U.S. __ (2018), 2018 WL 3073916.In a 5-4 opinion authored by Chief Justice Roberts, the Supreme Court held that even though CSLI data is maintained by the cell phone companies, the third party doctrine – which provides that information about an individual held by third parties falls outside the protections of the Fourth Amendment – does not apply to CSLI “in light of the deeply revealing nature of CSLI, its depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection.”2018 WL 3073916 at *15.


In 2012, Timothy Carpenter was arrested and charged with six counts of armed robbery for robbing stores in multiple locations in Michigan and Ohio. Carpenter’s arrest was based, in part, on CSLI data obtained by the government without a warrant under the Stored Communications Act from Carpenter’s two cell phone providers. The government had obtained 127 days of CSLI data from MetroPCS and two days of CSLI data from Sprint, which collectively showed 12,898 location points cataloging Carpenter’s movements, an average of 101 data points per day.2018 WL 3073916 at *4. The CSLI data showed that Carpenter (or at least his cell phone) was near four of the charged robberies at the time those robberies occurred. Id. at *5.Carpenter moved to suppress the CSLI data, arguing that the government had no right under the Fourth Amendment to obtain that data without a warrant supported by probable cause. Carpenter’s motion to suppress was denied by the District Court and Carpenter was subsequently convicted on all of the armed robbery counts, based in part on the CSLI data linking his cell phone to the locations of four of the robberies.Id.

On appeal, the Sixth Circuit affirmed Carpenter’s conviction, holding that Carpenter lacked a reasonable expectation of privacy in the CSLI data collected by the government because he had voluntarily shared that information with MetroPCS and Sprint. United States v. Carpenter, 819 F.3d 880 (2016). Relying on the Supreme Court’s third party disclosure cases, including Smith v. Maryland, 442 U.S. 735 (1979), the Sixth Circuit held that the CSLI data for Carpenter’s cell phone was not entitled to Fourth Amendment protection because Carpenter had voluntarily provided that data to MetroPCS and Sprint as a means of using his cell phone. Carpenter, 819 F.3d at 888.

The Supreme Court Reverses in a 5-4 Opinion

On June 22, 2018, the Supreme Court reversed the decision by the Sixth Circuit, holding that Carpenter’s CSLI data was entitled to Fourth Amendment protection even though it was maintained by MetroPCS and Sprint. The majority opinion was authored by Chief Justice Roberts, who was joined by Justices Ginsburg, Breyer, Sotomayor and Kagan. Justices Kennedy, Thomas, Alito and Gorsuch each filed a separate dissenting opinion. The majority and dissenting opinions are discussed below.

Chief Justice Robert’s Majority Opinion

Chief Justice Roberts begins by noting that the development of technology has forced the Court to find ways to preserve privacy from the government even when surveillance tools have enhanced the government’s ability to “encroach on areas normally guarded from inquisitive eyes.”2018 WL 3073916 at *6.He cites to several recent Court decisions, including Riley v. California, 573 U.S. __ (2014) and Kyllo v. United States, 533 U.S. 27 (2001), as examples of ways in which changes in technology have required the Court to take a more nuanced approach to Fourth Amendment cases. Addressing the facts in Carpenter, Chief Justice Roberts concludes that CSLI data does not fit under existing precedents and that it instead lies at the “intersection of two lines of cases,” the first addressing geolocation and the second addressing the Court’s third-party doctrine.

With respect to the Court’s geolocation decisions, Chief Justice Roberts acknowledges that in some of its decisions predating the digital era, such as United States v. Knotts, 460 U.S. 276 (1983),the Court had ruled that a driver should not expect his movements on public roads to be kept private. But, times have changed, says Chief Justice Roberts, and people would not expect the government to track their every movement over long periods of time without obtaining a warrant to do so. Chief Justice Roberts notes that because people carry their cell phones virtually everywhere with them, CSLI data provides the government with “near perfect surveillance, as if it had attached an ankle monitor to the phone’s user,” not only going forward, but also back in time as many as five years. 2018 WL 3073916 at *10.

Turning to the Court’s third-party doctrine cases, Chief Justice Roberts declines to extend the third-party doctrine to CSLI data, even though that data is always owned and controlled by the cell phone companies. He highlights the potential privacy impact of CSLI data, noting that “cell phone location information is detailed, encyclopedic, and effortlessly compiled.”2018 WL 3073916 at *10.Chief Justice Roberts distinguishes the Court’s earlier third party doctrine cases, including United States v. Miller, 425 U.S. 435 (1976) and Smith v. Maryland, 442 U.S. 735 (1979), noting that when those cases were decided, the Court was dealing with relatively limited types of personal information and that no one at the time could have imagined that cell phones would be so common and would provide so much information about their users for so long. He goes on to note that because cell phones are such a pervasive part of life, carrying one is necessary for participation in modern society. In this light, a cell phone user cannot be said to be voluntarily sharing information about his or her location with the cell phone company, which was the underlying rationale for the third party doctrine.

Chief Justice Roberts leaves the door open for the government to obtain CSLI data without a warrant in two circumstances. First, Chief Justice Roberts suggests that if the government seeks CSLI data for a short time period (fewer than seven days is mentioned in the opinion), then this might not constitute a Fourth Amendment search for which a warrant would be needed.2018 WL 3073916 at *9, fn 3. Second, the majority opinion would also make exceptions for emergencies, such as bomb threats, active shootings and child abductions.Id. at *15.

The Four Dissenting Opinions

Justice Kennedy, in a dissent joined by Justices Alito and Thomas, argues that CSLI data is not fundamentally different from other business records maintained by third parties and therefore there is no need for the Court to treat CSLI data any differently under the third-party doctrine. According to Justice Kennedy, no search within the meaning of the Fourth Amendment occurred because Carpenter should have had no expectation of privacy in CSLI data that he neither owned nor controlled. Justice Kennedy goes on to criticize the majority opinion for concluding that CSLI data somehow implicates greater privacy interests than the financial records and telephone records that the Court previously had held to be obtainable by the government without a warrant under the third party doctrine set forth in United States v. Miller, 425 U.S. 435 (1976) and Smith v. Maryland, 442 U.S. 735 (1979).2018 WL 3073916 at *16-29.

Justice Alito, in a dissent joined by Justice Thomas, echoes Justice Kennedy’s arguments and goes on to criticize the majority for a ruling that he predicts will likely lead to one of two undesirable outcomes. Either the majority opinion will, in future cases, be applied broadly to encompass all kinds of documents and data containing personal information (further eroding the third party doctrine), or subsequent cases will force the Court to qualify and limit its ruling in ways that have not yet been discovered, creating a “crazy quilt of the Fourth Amendment.”2018 WL 3073916 at *42-55.

Justice Thomas, having already joined the Kennedy and Alito dissents, also separately dissents to urge the Court to reconsider its use of the “reasonable expectation of privacy” test first enunciated by the Court in Katz v. United States, 389 U.S. 347 (1967), for Fourth Amendment cases. According to Justice Thomas, the reasonable expectation of privacy test set forth in Katz has no basis in the text or history of the Fourth Amendment and is unworkable in practice.2018 WL 3073916 at *30-41

Finally, Justice Gorsuch dissents to argue that the Court should not only abandon its use of the reasonable expectation of privacy test set forth in Katz, as advocated by Justice Thomas, but also abandon the third party doctrine in its entirety, rather than limit it as the majority opinion does. Justice Gorsuch would instead focus instead on whether an individual has a property interest in the records at issue.2018 WL 3073916 at *56-68.

Implications for the Future

While Chief Justice Roberts states that the Court’s decision is narrow and limited to the specific facts of the case before it (2018 WL 3073916 at *13), the decision is likely to have broad impact in future cases. As some commentators already have noted, there is no reason why the holding in Carpenter would not be equally applicable to a wide range of databases maintained by third parties containing sensitive and intimate information about millions of individuals. See, e.g., The Broad Reach of Carpenter v. United States, Paul Ohm, Gorsuch’s dissent, read with the majority opinion, also raises the question whether the third-party doctrine will ultimately survive at all in the digital age. 

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