The US Supreme Court is hearing arguments about the legality of so-called geofence warrants, sometimes also referred to as “digital dragnets” because they capture the location data of a great many innocent citizens in addition to criminal suspects.

In a practice raising obvious privacy concerns, tech giants are increasingly being asked by law enforcement to identify all of the smartphone users present at a particular location at the time a crime was committed …

CNET explains how geofence warrants work.

If there are no clear suspects for a crime, law enforcement can serve a warrant to a tech giant requesting location data. Police draw a circle on a map around a crime scene and specify a time window. The tech company (most frequently Google) searches its database for devices inside that “fence” during that time.…