Carpenter v. United States (2018)
Carpenter v. United States (2018): Warrant Required for Cell-Site Location Records
Historical CSLI reveals the “privacies of life” — police generally need a warrant.
Background
Investigators obtained months of Timothy Carpenter’s historical cell-site location information (CSLI) from his wireless carriers using court orders that did not require probable cause. The records placed his phone near several robberies. Carpenter argued that accessing this detailed location history without a warrant violated the Fourth Amendment.
Questions Presented
- Does obtaining historical CSLI from a third-party carrier constitute a search under the Fourth Amendment?
- Do officers generally need a probable-cause warrant to access this data?
Majority Opinion — Chief Justice John Roberts
Holding: Individuals have a legitimate expectation of privacy in long-term CSLI. Accessing it is a Fourth Amendment search that ordinarily requires a warrant supported by probable cause.
Roberts explained that CSLI provides an “encyclopedic” chronicle of a person’s life—home, work, church, doctor visits, and social patterns. Although the data is held by a third party, the traditional third-party doctrine does not control in this context because of the depth, breadth, and involuntary nature of CSLI creation. The Court carved a narrow but powerful rule: prolonged historical CSLI (and often even shorter spans in practice) requires a warrant; emergencies and other recognized exceptions may still apply.
For Texas cases, Carpenter is central to suppressing location evidence used in robbery, burglary, drug conspiracy, or assault investigations. Defense counsel in Montgomery County should examine whether the State used outdated pen register/2703(d) orders, the time span collected, and whether subsequent warrants relied on tainted CSLI. If so, move to exclude all fruits under both the U.S. and Texas Constitutions.