Police departments are reportedly forcing Google to hand over user data on those who were near crime scenes using “reverse location search warrants.”

“Police departments across the country have been knocking at Google’s door for at least the last two years with warrants to tap into the company’s extensive stores of cellphone location data,” reported Slate last month. “Known as ‘reverse location search warrants,’ these legal mandates allow law enforcement to sweep up the coordinates and movements of every cellphone in a broad area.”

“The police can then check to see if any of the phones came close to the crime scene. In doing so, however, the police can end up not only fishing for a suspect, but also gathering the location data of potentially hundreds (or thousands) of innocent people,” Slate continued, adding that there “have only been anecdotal reports of reverse location searches, so it’s unclear how widespread the practice is, but privacy advocates worry that Google’s data will eventually allow more and more departments to conduct indiscriminate searches.”

According to Slate, “WRAL was able to uncover four instances in which the Raleigh Police Department sought reverse-location data in 2017 for investigations into murder, sexual battery, and the suspected arson,” and police “were able obtain data for crimes that occurred as far back as 2015,” with just “one of the cases” resulting in arrest.

“The department reportedly got the idea to use reverse location searches after learning that the State Bureau of Investigation in Orange County, California, had also employed the technique,” Slate explained, while police departments in Minnesota reportedly “obtained at least 22 reverse-location search warrants since August.”

Slate noted that, “The warrants have, at times, sought location data in 33-hour windows, potentially giving officers information on tens of thousands of people. The warrants have sought to gather identifying data in crimes ranging from home invasions to a theft of $650 worth of tires. In one case, the reverse-location data was requested to help solve a fatal shooting from 2013.”

The FBI has also reportedly used the technique.

In a statement to Slate, Google claimed, “We have an established process for managing requests for data about our users, and in these particular instances, require a search warrant. We always push back on overly broad requests to protect our users’ privacy.”

You can read the full report at Slate.