Wired reports:

The FBI’s biggest-ever investigation included the biggest-ever haul of phones from controversial geofence warrants, court records show. A filing in the case of one of the January 6 suspects, David Rhine, shows that Google initially identified 5,723 devices as being in or near the US Capitol during the riot. Only around 900 people have so far been charged with offenses relating to the siege.

The filing suggests that dozens of phones that were in airplane mode during the riot, or otherwise out of cell service, were caught up in the trawl. Nor could users erase their digital trails later. In fact, 37 people who attempted to delete their location data following the attacks were singled out by the FBI for greater scrutiny.

Geofence search warrants are intended to locate anyone in a given area using digital services. Because Google’s Location History system is both powerful and widely used, the company is served about 10,000 geofence warrants in the US each year. Location History leverages GPS, Wi-Fi, and Bluetooth signals to pinpoint a phone within a few yards. Although the final location is still subject to some uncertainty, it is usually much more precise than triangulating signals from cell towers. Location History is turned off by default, but around a third of Google users switch it on, enabling services like real-time traffic prediction. [Continue reading…]