(April 24, 2026)

Background

The Supreme Court last weighed in on the digital Fourth Amendment in 2017. In Carpenter v. United States, the court addressed whether the police had to get a warrant before accessing a certain kind of digital location data, cell-site location information. Cell phones generate CSLI anytime they are on by scanning for the nearest cell tower with strong service. When a cell phone connects to a tower, that tower then records that connection in CSLI logs. A phone’s location can be tracked across time and space by reviewing those logs.

Writing for a 5-4 majority, Chief Justice John Roberts’ Carpenter opinion held that the police must get a warrant before reviewing seven or more days of CSLI for a person’s phone. (…)

Enter: geofence data

Among these unsettled questions is whether police need a warrant to access geofence data, another kind of digital location data. Geofence data generally refers to location information collected by cellphone apps. If you have encountered a prompt on your phone that asks you whether you’d like to allow an app to use your location, you’re likely generating the kind of data at issue in Chatrie. Chatrie specifically involved data generated by a Google service called Location History. In Google’s case, this location information was created by combining information from cell towers but also on GPS, Wi-Fi, and Bluetooth signals.