Investigators turned to a "geofence" search warrant when they noticed people using cell phones in security footage of a gunfight at a northern Virginia motel, reports the Washington Post. A powerful new tool, "geofence" warrants ask Google to list all cellphones active in a given crime scene to help police crack cases. They have been used to find suspects in cases from bank robberies to the Jan. 6, 2021 riot in Washington. Authorities receive a list of anonymous numbers associated with the devices in the area, which they then ask Google to unmask. These types of warrants have ballooned 600 percent in Virginia and 1,200 percent nationwide.