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Cellphone dragnets can help catch criminals. Judges say they can also violate constitutional rights.

Police requests for ‘geofence’ data showing active cellphones near crime scenes have skyrocketed

Police used warrants to seek location histories kept by Google of cellphones and other devices used within 500 feet of the Call Federal Credit Union building in Midlothian, Va. (Steve Helber/AP)

A detail caught the eye of police who were investigating a gunfight that occurred after a party at a Northern Virginia motel: Many of those involved could be seen on security camera footage using cellphones.

Fairfax County detectives turned to a powerful and controversial new investigative tool. They asked a judge to approve a kind of digital dragnet — a request for Google to list all cellphones its data shows were active in an area around the crime scene.

Such “geofence” search warrants have exploded nearly 600 percent in Virginia in recent years and 1,200 percent nationwide, according to Google. They have helped police crack bank robberies, find suspects in killings and ferret out people who were present at the Jan. 6 riot in Washington.

But in a first-of-its-kind opinion in Virginia, a Fairfax County judge ruled late last month that the motel request was so indiscriminate that it violated the constitutional safeguards against unreasonable searches, because, in possibly revealing information about the gunmen, it would sweep up information about motel guests who had nothing to do with the shooting. A federal judge in Richmond followed with an opinion in a robbery case that raised even broader concerns about the tool.

The rulings are likely to reverberate across Virginia and the nation as a debate over the legality of geofence warrants intensifies with their proliferation. A handful of other federal magistrate judges have turned down applications for geofence warrants, but in the vast majority of cases, they have been approved with few questions until now.

“The innocent motel patrons uninvolved in the shooting have constitutional privacy interests in their location,” Fairfax County Circuit Court Judge David A. Oblon wrote in his opinion. “To search them, police must persuade the Court there is probable cause to do so.”

Geofence warrants are a fundamental departure from the way law enforcement has typically sought search warrants. In most cases, investigators identify a suspect in connection with a crime and then seek permission from a court to search a home, a car or an electronic device associated with that person.

But when police have not zeroed in on a suspect, a geofence warrant may help jump-start an investigation. They ask Google to provide an anonymized list of cellphones active within the virtual boundary of a geographic zone around the crime scene during a particular period.

Over the past decade, Google has collected location data from hundreds of millions of devices that use Android software, have accessed Google websites or have certain apps, such as Google Maps. Location history is off by default, but Google often prompts users to turn it on when they use its products.

Once authorities get the list of anonymized numbers, they review it and ask Google to unmask identifying information for cellphones they think might be related to the crime.

Geofence warrant requests in Virginia grew from 72 in 2018 to 484 in 2020, the last year for which data is available, according to Google. Nationwide, the numbers surged from nearly 1,000 to more than 11,500 during the same period. Law enforcement investigators have also made geofence requests to tech companies including Apple, Snapchat and Uber.

The explosive growth in the use of such warrants has alarmed privacy and civil liberties advocates.

Albert Fox Cahn, the executive director of the Surveillance Technology Oversight Project (STOP), is part of a coalition calling for a moratorium on the use of geofence warrants. STOP also backs a bill in the New York legislature that would enact the nation’s first ban on geofence warrants.

Cahn said geofence warrants undermine the Fourth Amendment to the Constitution, which requires that authorities have probable cause for a search and that they describe the things that are to be seized, known in legal parlance as “particularity.”

“With geofence warrants, you are almost violating that every time,” Cahn said. “These warrants are so broad, you are capturing information on people you know are not suspects.”

Cahn pointed to two cases in which innocent people were arrested and accused of crimes they did not commit after their cellphone data was obtained through geofence warrants.

One involved an Arizona man who was arrested in a killing after his phone was placed at the scene of the crime. The case was dropped after authorities discovered that he had lent his phone to another man, who was eventually charged in the slaying. In the other case, a Florida man simply biked by the scene of a burglary several times on the day it occurred, raising authorities’ suspicions.

In a third case highlighted by Cahn as unsettling, Manhattan prosecutors used a geofence warrant to try to locate antifascists who were attacked by Proud Boys while protesting an appearance of the founder of the far-right group in New York City.

In the motel shooting, Fairfax County police sought a geofence warrant after two groups of people opened fire on each other in the parking lot following a party. Oblon redacted specific details about the shooting in his ruling, including its time and location, so as not to impede the police investigation. Fairfax police said that no one was injured and that no arrests have been made.

Police asked Oblon to approve a geofence warrant for an area that included the motel, parking lot and grounds of the property for a period of nearly three hours. Geofence warrants vary widely in their geographic size from a few rooms to multiple city blocks and can collect data on a handful of phones or hundreds.

Oblon wrote that police had not established that the vast majority of motel guests were involved in any crime, so they did not have probable cause to search them, and he found that the search requested was overly broad “as to size, time and location.”

He also opined that police had too much discretion in deciding which cellphones to unmask and cast doubt on a request by investigators to give them authority to expand the zone of the search if they felt it was necessary. Oblon called the request the “proverbial blank check.”

“Police are targeting a particularly sensitive area,” Oblon wrote. “Motels are close proxies to home on one’s scale of privacy expectations.”

Anthony Guglielmi, a spokesman for the Fairfax County police, said the department “respect[s] the decision of the court” and will incorporate Oblon’s findings into its training on how investigators use geofence warrants. Guglielmi said the department does not have figures on how many applications for geofence warrants it has filed in recent years.

The federal case has been closely watched by privacy advocates and is likely to be even further-reaching, since U.S. District Judge M. Hannah Lauck spent two years examining how geofence warrants work.

The case stemmed from a Chesterfield County robbery, during which an armed man entered the Call Federal Credit Union in 2019 and forced the manager to give him $195,000. The only solid information law enforcement had was that the robber was holding a cellphone.

On that basis, a detective obtained a warrant for Google to search for any phones that were within a 17.5-acre area around the bank that included a church, apartments, busy roads and a parking lot. The request sought an hour of data. That request was revised to two hours of location data on 19 devices identified by the company.

When Google, following its own legal process, said that was too much information, the detective narrowed his request to nine of the 19 devices and then identifying information on three. A 27-year-old, Okello Chatrie, was ultimately identified and charged but challenged the search.

Chatrie’s attorneys argued that geofence warrants violate the Constitution and that the evidence in Chatrie’s case should be thrown out.

Lauck did not suppress the evidence, writing in her opinion that the detective who conducted the search acted in good faith and had no reason to know that his actions were unconstitutional, but she took aim at geofence warrants generally.

She said the geofence warrant in Chatrie’s case “lacked any semblance of … particularized probable cause” and “swept in unrestricted location data for private citizens who had no reason to incur Government scrutiny.” Among those were people inside their homes, she noted.

Lauck urged lawmakers to address her “deep concern … that current Fourth Amendment doctrine may be materially lagging behind technological innovations.”

Lauck noted in her opinion that the geofence warrant was signed by a magistrate with no law degree. It was Google, not a court, that demanded that the police limit their search. And although the data is anonymized, a defense expert showed that it is often easy to identify users on the basis of the locations where they spend the most time. The evidence also showed how broad the search was: One person whose data was included appears to have merely driven by the area of the robbery.

“This case has arisen because no extant legislation prevents Google or its competitors from collecting and using this vast amount of data,” Lauck wrote. “Thoughtful legislation could not only protect the privacy of citizens, but also could relieve companies of the burden to police law enforcement requests for the data they lawfully have.”

Prosecutors and Chatrie’s public defender declined to comment on the ruling, which could be appealed to a higher court.

Google said in a statement that it strives to protect users’ privacy when it comes to complying with geofence warrants. The company said that it began seeing requests for geofence warrants in 2016 and that the number of warrants began to increase noticeably in 2018.

“We developed a process specifically for these requests that is designed to honor our legal obligations while narrowing the scope of data disclosed,” the statement read.