Where Were You? Geofence Warrants and the Fourth Amendment’s Day in Court

by Dennis Crouch

One of the topics I teach in my internet law course is the steady erosion of the boundary between digital and physical privacy. For years, privacy debates centered on what we do online: how we scroll, what we buy, who we email. But location tracking has collapsed that distinction. Your phone knows where you sleep, which doctor you visit, and whether you attended a protest. And because that data is collected continuously, stored indefinitely, and held by private companies, it is available to law enforcement with the right legal process. The question the Supreme Court will take up in April is just how much process the Fourth Amendment requires.

In Chatrie v. United States, No. 25-112, the Court is hearing its first case addressing the constitutionality of geofence warrants. A geofence warrant works differently from a traditional warrant. Instead of identifying a suspect and then seeking evidence, law enforcement identifies a location and a time window and then asks a technology company to hand over data on every device that was nearby. In this case, a detective investigating a 2019 bank robbery in Midlothian, Virginia, obtained a warrant directing Google to search its Sensorvault database, which at the time held continuous location records for over 500 million users of Google's Location History service. The warrant defined a geofence with a 150-meter radius centered on the bank and a one-hour window around the robbery.

Google's initial search returned anonymized location data for 19 devices in the zone. What followed was a three-step process designed by Google. The detective, without returning to a judge, selected nine of the 19 accounts for expanded tracking over a two-hour window with no geographic limits. He then asked Google to de-anonymize three of those accounts, again without judicial approval. One belonged to Okello Chatrie.