Can cops use digital dragnets to track you?

A years-old bank heist may soon have major privacy implications for every American who owns a cellphone. On Monday, the Supreme Court heard arguments in Chatrie v. United States, a case involving police’s use of controversial “geofence warrants” to find and arrest Okello Chatrie, the suspect of a 2019 bank robbery outside Richmond, Virginia. At stake is how private your location data — and any other information you store with a large tech company — actually is.

Chatrie was tracked down via the Location History feature on Google Maps, which can identify a person’s location within three meters and refreshes every two minutes. Police served Google with a warrant asking for data on anyone who had been within 300 meters of the Call Federal Credit Union at the time of the robbery, and made subsequent requests for users’ information until they identified Chatrie as the prime suspect.

Chatrie’s attorney argues that the geofence inquiry constituted an unreasonable search and seizure and therefore violated the Fourth Amendment. A federal district court agreed, determining that police didn’t have probable cause for a geofence warrant — but the court ultimately sided with the government, using the “good faith exception” to justify the legality of the otherwise unconstitutional search. A federal appeals court not only upheld the government’s position but also ruled that the Fourth Amendment hadn’t been violated at all, since Chatrie had voluntarily shared his location information with Google. Following today’s arguments, the Supreme Court will issue a ruling in the coming months.

Google stopped storing Maps users’ location history in the cloud in 2024, citing privacy concerns — a change that led some justices to question why the court was taking up this issue in the first place. “This involves a Google feature that doesn’t exist any longer,” Justice Samuel Alito said during Monday’s oral arguments. “You’re asking for a law review article on a subject that is largely unexplored by our precedents.”

But plenty of other companies track users’ location data: Uber, Lyft, and Snap, to name a few, not to mention the scores of other apps that monitor and store information on users’ whereabouts. “Chatrie could have fairly major implications in other digital search cases, especially ‘reverse searches’ like this case where police do not have an identified suspect, account, or device,” Andrew Crocker, the surveillance litigation director at the Electronic Frontier Foundation, told noti.group. (The EFF filed an amicus brief in the case.)

Detectives sent Google a geofence warrant after hitting a dead end in their 2019 investigation of the robbery. Google first provided semi-anonymized information on 19 users, according to The New Republic. The detective investigating the case then sent a follow-up request for nine users’ data, providing no explanation on “why he chose the nine accounts,” and then asked Google to de-anonymize three of those accounts. This information led police to Chatrie.

Adam Unikowsky, Chatrie’s attorney, described these actions as “bad police work.” Some justices seemed skeptical. Justice Brett Kavanaugh, for example, said the police work in the Chatrie investigation “should be applauded.”

One of the questions at the heart of the case is whether accessing geofence information counts as a “search” at all. The court uses two methods to assess this, said Brent Skorup, a legal fellow at the libertarian Cato Institute, which submitted an amicus brief in the case. The first involves property interests — whether a trespass was committed during a search of a house, for instance, or someone’s diary. The second involves whether basic privacy rights were violated, even in cases where no property is at stake.

The core argument in Chatrie, Skorup explained, was that Chatrie owned his location history records and Google was holding them on his behalf in something akin to a virtual locker, just like a bank holds someone’s money. “We give our property to third parties all the time,” Skorup said. “If you mail a letter or put something in a safe deposit box, you still own the property even if you’re entrusting it to others.”

On Monday, most justices seemed skeptical of the property argument. But Chatrie’s attorneys made another argument using what’s known as the Katz test. Under the precedent set by Katz v. United States, even if no property is involved, a search can occur if it violates a person’s expectation of privacy — including instances where police bugged a telephone booth, or obtained cellphone tower records, both without a warrant. The latter was the subject of Carpenter v. United States, a 2018 case in which the court ruled that police must generally get a warrant to seize cellphone tower location records.

Carpenter, the last major Fourth Amendment case taken up by the court, may serve as a precedent for Chatrie — but the composition of the court has changed significantly since 2018. The court was split in Carpenter, ultimately ruling 5-4 in favor of a warrant requirement. Two of the justices involved in that ruling have since left the bench: Anthony Kennedy retired in 2018, and Ruth Bader Ginsburg died in 2020. Their replacements, both appointed by President Donald Trump, tend to side with the government. But the court’s conservative composition isn’t a guarantee for the administration.

Though Chief Justice John Roberts noted that users could opt out of the Location History feature — “If you don’t want the government to have your location history, you just flip that off,” he said — he also asked the government’s attorney about the far-reaching implications of letting police seize people’s location data without a warrant. “What’s to prevent the government from using this to find out the identities of everyone at a particular church, a particular political organization?” Roberts asked. “What are the restraints that would prevent that from becoming a problem?” In 2020, police used geofence warrants to investigate protesters in connection with Black Lives Matter protests in Kenosha, Wisconsin, searching for the suspect in an arson case.

“Chatrie is making a very broad argument that, essentially, some databases are too large to search — even with a warrant,” Stanford Law School professor Orin Kerr told noti.group. “If the Court were to accept that, it would have lots of implications: It would presumably strike down all warrants for Google search terms, tower dumps, and other technologies.”

Though police did obtain a warrant to obtain the location data that led them to Chatrie, the government claimed they didn’t need to — an argument some justices found troubling.

“The stakes are quite large” in Chatrie, says Skorup — far beyond the scope of a discontinued Google feature or even location tracking as a whole. “A lot of the issues here apply to other areas. Location history is one factor, but each of us — most of us — have our personal, private records stored with a large tech company.”

“They say location is different,” Skorup said, explaining the government’s argument. “If the government is correct that no searches occur when you turn records over to a large digital company, the government could get all these records without a warrant, and then the Fourth Amendment is rendered quite hollow if that’s the case.”