Carpenter v. United States

Incident Summary & Facts

In 2011, police arrested four men suspected of robbing a series of Radio Shack and T-Mobile stores in Detroit. One confessed that the group had robbed nine stores in Michigan and Ohio over four months, named 15 accomplices, and gave the FBI some of their cell phone numbers. Without a warrant, prosecutors obtained court orders under the Stored Communications Act, 18 U.S.C. § 2703(d), which requires only “reasonable grounds” to believe records are “relevant and material” to an investigation. The orders directed Timothy Carpenter’s wireless carriers to disclose his historical cell-site location information (CSLI). MetroPCS produced 127 days of records; Sprint, asked for seven days, produced two. In all, the Government obtained 12,898 location points, an average of 101 per day.

Carpenter was charged with six counts of robbery and six counts of carrying a firearm during a federal crime of violence; Justice Kennedy’s dissent describes the robberies as committed “at gunpoint.” His motion to suppress the CSLI was denied. At trial, an FBI agent used the records to place Carpenter’s phone near four of the robberies, and he was convicted and sentenced to more than 100 years. The Sixth Circuit affirmed under the third-party doctrine, and the Supreme Court granted certiorari.

This case did not involve a use-of-force encounter; it concerns digital location records and the Fourth Amendment’s warrant requirement.

Core Legal Issue

Whether the Government conducts a Fourth Amendment search when it accesses historical cell-site records that provide “a comprehensive chronicle of the user’s past movements,” and, if so, whether a § 2703(d) order is enough without a warrant supported by probable cause.

The Holding

The Government’s acquisition of Carpenter’s CSLI was a search, and the Government “must generally obtain a warrant supported by probable cause before acquiring such records.” The Sixth Circuit’s judgment was reversed and the case remanded (5–4).

The Court’s Analysis (Roberts, C.J.):

• The whole of one’s movements: Drawing on Knotts and the Jones concurrences, “individuals have a reasonable expectation of privacy in the whole of their physical movements.” A person “does not surrender all Fourth Amendment protection by venturing into the public sphere.”
• Why CSLI is different: It is “detailed, encyclopedic, and effortlessly compiled.” Because a phone follows its owner almost everywhere, tracking it achieves “near perfect surveillance, as if it had attached an ankle monitor.” Its “retrospective quality” lets police “travel back in time.” Imprecision did not matter, because “inference [does not] insulate[] a search.”
• Third-party doctrine not extended: Smith and Miller do not cover this “distinct category of information.” Carrying a phone is “indispensable to participation in modern society,” and CSLI is generated without any affirmative act, so it is not truly “shared.”
• Warrant required; exigency preserved: A § 2703(d) showing “falls well short of the probable cause required for a warrant.” Exigencies (a fleeing suspect, imminent harm, destruction of evidence, bomb threats, active shootings, child abductions) may still justify warrantless access. Accessing seven days of CSLI is a search.
• Narrow ruling: The Court did not decide real-time CSLI or “tower dumps,” and did not “call into question conventional surveillance techniques and tools, such as security cameras.”
• Dissents: Kennedy, J. (joined by Thomas and Alito, JJ.): the records were the carrier’s business records under Miller/Smith. Thomas, J.: the Katz test should be reconsidered. Alito, J. (joined by Thomas, J.): compulsory process is not an actual search, and the ruling threatens subpoena practice. Gorsuch, J.: a property and positive-law approach would be better, and Carpenter forfeited that argument.