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Law Enforcement Agencies Need a Warrant to Access Cellphone Location Data, Supreme Court Rules

The Supreme Court has ruled that law enforcement must obtain a warrant before tracking an individual’s cellphone location data over an extended period of time — a significant win for those who advocate for increased privacy rights and view government interference with data obtained by cellphone companies as a constitutional infringement.

Carpenter v. United States, a landmark case, was decided in a 5-4 ruling on Friday and marks the first time the Supreme Court has made a ruling regarding cellphone location data.

The case stems from a 2011 robbery trial in Detroit when police mustered months worth of cellphone location data from plaintiff Timothy Carpenter’s cellphone provider, MetroPCS. Officials were able to compile a comprehensive map of his 12,898 different locations over the course of 127 days. In 2016, a Sixth Circuit Court of Appeals judge decided that cellphone location data was not protected under the Fourth Amendment protection against unreasonable search and seizure and, therefore, should not require a warrant.

Delivering the majority opinion, Chief Justice John Roberts reversed and remanded the Court of Appeal’s initial ruling, defending the decision on the grounds of Fourth Amendment rights to privacy and security.

“We decline to grant the state unrestricted access to a wireless carrier’s database of physical location information,” Roberts wrote. “In light of the deeply revealing nature of the [cell-site location information], 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.”