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. The police can then ask the company for the specific account details — such as email addresses, phone numbers and usernames.…