Cell-site location information ("CSLI") is location information generated by cellular phone providers that indicates which cell tower a particular phone was communicating with when a communication was made. United States v. Curtis, No. 17-1833, 2018 WL 4042631, at *1 (7th Cir. Aug. 24, 2018). It is capable of pinpointing a phone's location within 50 meters. Id. Because cell phones are in constant communication with the nearest cell site—often affixed to a cell tower—they can collect CSLI as frequently as several times a minute. Id.
In June 2018, in Carpenter v. United States, 138 S. Ct. 2206 (2018), the Supreme Court extended Fourth Amendment protection to CSLI and held that the government conducts a "search" when it accesses historical cell phone records that provide a comprehensive chronicle of the user's past movements. The Court concluded that the government must generally obtain a warrant supported by probable cause before acquiring such records and rejected application of the "third-party doctrine," even though the records at issue were held by a wireless carrier.Read More