by Caroline Bottger
A Florida man on his daily bike route was suddenly a suspect in a burglary when Google data placed him near the scene of the crime. Using a geofence warrant, law enforcement placed Zachary McCoy near a house that had been burgled 10 months ago. The only problem was, McCoy was innocent, and the house is part of his usual route around the neighborhood.
Geofence warrants are requests for mobile location data made by law enforcement to tech companies – in this case, Google. This data, called Location History, has been available since 2009. Law enforcement can see which mobile devices passed through a certain area, or ‘geofence,’ at a certain time. From there, they get a pool of potential suspects. In an extensive feature on geofence warrants, The New York Times called this a ‘dragnet’ approach.
The availability of such granular data is attractive to law enforcement. Last year, Google said that the number of geofence warrants by law enforcement has skyrocketed: it has seen a 1,500 percent increase year over year. Geofence warrants have been used to solve robberies, murders, arsons, and rapes, even a string of bombings in Austin, TX in 2018.
But geofence warrants present significant legal issues. Traditionally, police need to establish probable cause before issuing a warrant. With geofence warrants, police work “backwards,” according to Lawfare, and gather a large amount of information before identifying probable cause. This practice implicates the Fourth Amendment, which prohibits “unreasonable search and seizures” of citizens. In November 2019, a 24-year-old man convicted of burglary lodged the first Fourth Amendment challenge concerning the geofence warrant that led to his arrest. In U.S. vs. Chatrie, the defense argued that Google location data is by its nature more invasive than cell phone records, and that the defendant did not voluntarily share his data with Google.