Last May, an armed man fled the Call Federal Credit Union in Midlothian, Virginia, with $195,000 in stolen money. While reviewing the bank’s video surveillance feed, Chesterfield Police Department investigators noted the suspect held a cellphone to his ear prior to demanding personnel hand over the cash. That prompted them to request a warrant to obtain location data from Google to help identify the man. The process, known as a geofence warrant, uses data collected from devices and apps developed by Google — like Android phones, Google maps and Gmail — to determine individuals’ locations at given dates and times.

In this case, police asked for data on all cellphones within a 150-meter radius of the bank during the hour of the robbery. They received a list of 19 devices. The cops went back to Google for additional location data for nine of the identified accounts. Of those, three devices piqued their interest, so for a third time, investigators asked Google for subscriber information. One of the phones proved to be inside the bank at the time of the robbery, leaving the premises immediately afterward and tracking the same path the suspect traveled according to witness accounts.

From the Google profile information, officers pinpointed an email, phone number and name, which led to the arrest of Okello Chatrie, who’s been charged with armed robbery.

Geofence warrants have replaced cell tower pings as a means to locate individuals, and have become a popular tool for law enforcement, with documented cases in North Carolina, Minnesota, Virginia and Arizona. NBC News reports that the number of search warrants presented to Google has more than doubled over the past two years.

However, these warrants aren’t without controversy. Opponents suggest that casting a large net to capture data from all individuals within a given perimeter violates innocent persons’ guarantee against unreasonable searches spelled out in the Fourth Amendment. In fact, that’s the argument Chatrie’s attorney asserts.

“Without the name or number of a single suspect and without ever demonstrating any likelihood that Google even has data connected to a crime, law enforcement invades the privacy of tens or hundreds or thousands of individuals just because they were in the area,” Michael Price wrote in a court filing.

Prosecutors, however, argued that because Chatrie had opted in to Google’s location services, allowing the company’s apps to track his movements, the search was legal. Furthermore, they pointed out in their response, police were careful to avoid collecting personal information from anyone unconnected to the robbery: “The geofence warrant allowed them to solve the crime and protect the public by examining a remarkably limited and focused set of records from Google.”

It may be some time before the courts opine on whether geofence warrants break the bounds of the Fourth Amendment. Just last year, the U.S. Supreme Court issued an opinion that determined cellphone providers must be served warrants before giving law enforcement cell tower location records. That case originated more than a decade ago and did not involve modern smartphone technology, so it’s unclear whether that finding can be applied to geofence warrants, too. In the meantime, they remain a potentially powerful tool for law enforcement.