The NCSL Blog


By Lisa Soronen

Fourth Amendment watchers have known the U.S. Supreme Court would agree to decide a cell-site location case sooner rather than later. With a full bench, the court has agreed to review United States v. Carpenter.

People using cellphones on a subway platform in New York. A new case concerns historical data held by cellphone companies that shows users’ movements over time and could, for instance, place them at the scene of a crime. Credit Hiroko Masuike/The New York Times In this case, the court will decide whether police must obtain warrants per the Fourth Amendment to require wireless carriers to provide cell-site data.

State and local governments have an interest in obtaining cell-site data as quickly and easily as possible as it can provide solid evidence a particular person was near the scene of a crime.

Cellphones work by establishing a radio connection with the nearest cell tower. Towers project signals in different directions or “sectors.” In urban areas, cell sites typically cover from between a half-mile to two miles. Wireless companies maintain cell-site information for phone calls.

Cell-site data showed that Timothy Carpenter and Timothy Sanders placed phone calls near the location of a number of robberies around the time the robberies happened.

The federal government obtained the cell-site data from Carpenter’s and Sanders’ wireless carriers using a court order issued under the Stored Communications Act, which requires the government to show “reasonable grounds” for believing that the records were “relevant and material to an ongoing investigation.” The defendants argued obtaining the information was a “search” under the Fourth Amendment requiring a warrant.

The 6th U.S. Circuit Court of Appeals held that obtaining the cell-site data does not constitute a search under the Fourth Amendment because while “content” is protected by the Fourth Amendment “routing information” is not.

The 6th Circuit analogized this case to Smith v. Maryland (1979) where the Supreme Court held that police installation of a pen register—a device that tracked the phone numbers a person dialed from his or her home phone—was not a search. “Although [the caller’s] conduct may have been calculated to keep the contents of his conversation private, his conduct was not and could not have been calculated to preserve the privacy of the number he dialed.”

The lower court noted that cell-site data are business records obtained from a third party (a wireless company) and that defendants have a lower expectation of privacy in such records.

The lower court also noted that Congress struck a balance in the Stored Communications Act between full Fourth Amendment protection and no Fourth Amendment protection, and that Congress is better equipped than courts when it comes to new technologies to “evaluate empirical questions that underlie . . . constitutional judgments.”

Lisa Soronen is executive director of the State and Local Legal Center and a frequent contributor to the NCSL Blog on judicial issues.

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This blog offers updates on the National Conference of State Legislatures' research and training, the latest on federalism and the state legislative institution, and posts about state legislators and legislative staff. The blog is edited by NCSL staff and written primarily by NCSL's experts on public policy and the state legislative institution.