Cell Site Location Information Deserves Privacy Protections

This week, CDT joined an amicus brief filed by the American Civil Liberties Union in a Ninth Circuit location privacy case, United States v Gilton. The brief argues that law enforcement should have to get a warrant to obtain cell site location information (CSLI) from a provider. CDT had previously argued, in a petition it joined to the Supreme Court in another location privacy case, that the Fourth Amendment warrant requirement should protect CSLI, which can reveal sensitive personal information, such as political, religious, and sexual associations.

The information obtained in this case was particularly revealing. Law enforcement received 37 days of historical CSLI, comprising 8,790 cell site location data points, an average of 237.6 points per day, or one every six minutes. This data revealed granular information about Gilton’s movements and location, including when he was inside his home and when he spent the night elsewhere.

The district court held that people have a reasonable expectation of privacy in their historical CSLI held by a service provider, and that a valid warrant was required. The Ninth Circuit should affirm the lower court’s ruling and help to finally bring the Fourth Amendment into the 21^st Century.