It is unclear how often these search requests have led to arrests or convictions, because many of the investigations are still open and judges frequently seal the warrants. The practice was first used by federal agents in 2016, according to Google employees, and first publicly reported last year in North Carolina. It has since spread to local departments across the country, including in California, Florida, Minnesota and Washington. This year, one Google employee said, the company received as many as 180 requests in one week. Google declined to confirm precise numbers.
The technique illustrates a phenomenon privacy advocates have long referred to as the “if you build it, they will come” principle — anytime a technology company creates a system that could be used in surveillance, law enforcement inevitably comes knocking. Sensorvault, according to Google employees, includes detailed location records involving at least hundreds of millions of devices worldwide and dating back nearly a decade.
The new orders, sometimes called “geofence” warrants, specify an area and a time period, and Google gathers information from Sensorvault about the devices that were there. It labels them with anonymous ID numbers, and detectives look at locations and movement patterns to see if any appear relevant to the crime. Once they narrow the field to a few devices they think belong to suspects or witnesses, Google reveals the users’ names and other information.
‘‘There are privacy concerns that we all have with our phones being tracked — and when those kinds of issues are relevant in a criminal case, that should give everybody serious pause,” said Catherine Turner, a Minnesota defense lawyer who is handling a case involving the technique.