Recent Developments Concerning Geofence Warrants

Five years ago, I wrote about geofence warrants. I said then that “there are zero cases on Westlaw . . . [and] virtually no secondary source material about these warrants.” Times have changed. Now we have cases, including one from the Fourth Circuit, and lots of secondary source material. This post explains the state of the law on geofence warrants. The basics of geofence warrants. Geofence warrants normally are used when police know that a crime occurred at a specific time and place, but do not yet have a suspect. These warrants require a technology company – almost always Google – to search its database of user location information and to produce information about users who were near the place in question around the time of the crime. Google receives tens of thousands of these warrants each year, because about one third of its registered users, meaning over 500 million people, have enabled a feature called Location History that more or less continuously shares the location of the user’s phone with Google. Google has developed a multi-step protocol for responding to these warrants. It initially shares anonymized data, then after law enforcement selects the accounts of greatest interest, shares users’ names and other identifying information. What’s the controversy? Law enforcement views these warrants as vital tools for developing leads in cases where traditional investigative techniques have failed, and prosecutors often argue that any privacy intrusion is slight given the short time frame and limited geographic area at issue. Critics view these [...]