A federal magistrate judge in San Jose, California denied a government request for historical cell site records, ordering the government to seek a search warrant for the information. The government appealed this order to U.S. District Judge Lucy Koh who requested the Federal Public Defender argue why the Fourth Amendment would require law enforcement use a search warrant to obtain this information. EFF filed an amicus brief supporting the Federal Public Defender and explaining as an increasing number of state courts and legislatures adopt a warrant requirement for cell site records, the expectation that these records remain private is necessarily reasonable. Our brief also explained the warrant requirement is particularly important in California where the state Supreme Court rejected the so-called “third party doctrine,” the idea that you lose an expectation of privacy over records shared with a third party, more than thirty years ago. Instead, the state constitution protects telephone records with an expectation of privacy.

In July 2015, Judge Koh agreed with us and found the Fourth Amendment protected historical cell site records and required law enforcement use a warrant to obtain these records.