On Monday, the U.S. Supreme Court considered arguments in a pivotal legal case that could reshape digital privacy rights for individuals throughout the United States.

The case, Chatrie v. United States, revolves around the contentious use of “geofence” search warrants by the government. Law enforcement and federal agents utilize these warrants to compel technology firms, such as Google, to provide data regarding which of its billions of users were present in a specific location and time based on their phones’ geographical positioning.

By broadly capturing a tech firm’s repository of user location information, investigators can deduce who was present at a crime scene, essentially enabling authorities to identify potential criminal suspects like searching for a needle in a digital haystack.

However, advocates for civil liberties have consistently argued that geofence warrants are fundamentally excessive and unconstitutional as they retrieve information about individuals who were nearby but have no relation to the alleged event. In numerous instances over recent years, geofence warrants have ensnared innocent individuals who were merely present by chance, whose private information was requested nonetheless, been improperly filed to obtain data extending beyond their intended scope, and utilized to pinpoint individuals attending protests or other lawful gatherings.

The utilization of geofence warrants has surged within law enforcement communities over the past decade, with a New York Times investigation revealing that the practice was first employed by federal agents in 2016. Every year since 2018, federal agencies and police departments across the U.S. have submitted thousands of geofence warrants, which constitute a significant percentage of the legal requests received by technology firms like Google, which maintain extensive databases of location data amassed from user searches, maps, and Android devices.

Chatrie is the first significant Fourth Amendment case that the Supreme Court has reviewed this decade. The ruling could determine the legality of geofence warrants. Much of the case hinges on whether individuals in the U.S. possess a “reasonable expectation” of privacy regarding information gathered by tech giants, such as location data.

It remains unclear how the nine justices of the Supreme Court will cast their votes — a ruling is anticipated later this year — or if the court will demand an outright cessation of the controversial method. However, the discussions held before the court on Monday provide insight into the justices’ potential perspectives on the matter.

“Search first and develop suspicions later“

The case centers on Okello Chatrie, a Virginia man found guilty of a bank robbery in 2019. At that time, police observed a suspect on the bank’s surveillance footage talking on a cellphone. Investigators subsequently executed a “geofence” search warrant against Google, compelling the company to supply data on all phones that were within a short distance of the bank and within an hour of the robbery.

In practice, law enforcement can delineate an area on a map around a crime scene or another significant location, and request to sift through vast amounts of location data from Google’s databases to identify anyone who was present at a specific moment.

In response to the geofence warrant, Google provided extensive anonymized location data pertaining to its account holders who were in the vicinity during the robbery, after which investigators sought additional details regarding some accounts that were near the bank for several hours leading up to the incident.

Police then received the identities and associated details of three account holders — one of whom they identified as Chatrie.

Chatrie ultimately pleaded guilty and received a prison sentence exceeding 11 years. However, as his case advanced through the legal system, his defense contended that the evidence gathered through the geofence warrant, which allegedly connected him to the crime scene, should not have been admissible.

A crucial aspect of Chatrie’s argument invokes a point frequently cited by privacy advocates to advocate for the unconstitutionality of geofence warrants.

The geofence warrant “permitted the government to search first and develop suspicions later,” they assert, emphasizing that it contradicts the longstanding tenets of the Fourth Amendment that establishes safeguards against unreasonable searches and seizures, including those involving individuals’ data.

As noted by the Supreme Court observation site SCOTUSblog, one of the lower courts concurred that the geofence warrant failed to establish the necessary “probable cause” linking Chatrie to the bank robbery, which warranted the initial geofence warrant.

The argument suggested that the warrant was too vague as it did not specify the particular account that contained the data the investigators sought.

Nonetheless, the court permitted the evidence to be used against Chatrie, determining that law enforcement had acted in good faith when obtaining the warrant.

According to a blog entry by civil liberties attorney Jennifer Stisa Granick, an amicus brief from a coalition of security researchers and technologists provided the court with what was deemed the “most intriguing and significant” argument to inform its eventual ruling. The brief contends that the geofence warrant in Chatrie’s case was unconstitutional as it mandated Google to actively sift through data stored in the individual accounts of hundreds of millions of Google users for the details that the police required, a practice at odds with the Fourth Amendment.

The government, on the other hand, has predominantly maintained that Chatrie “affirmatively chose to enable Google to gather, store, and utilize” his location data, arguing that the warrant “merely instructed Google to locate and provide the requisite information.” The U.S. solicitor general, D. John Sauer, representing the government before Monday’s hearing, indicated that Chatrie’s “arguments seem to imply that no geofence warrant, of any kind, could ever be executed.”

After a divided decision on appeal, Chatrie’s attorneys urged the U.S. Supreme Court to take on the case to determine the constitutionality of geofence warrants.

Justices appear mixed after hearing arguments

While the case is unlikely to impact Chatrie’s sentencing, the Supreme Court’s judgment could have broader ramifications for the privacy of Americans.

Following livestreamed oral arguments between Chatrie’s attorneys and the U.S. government in Washington on Monday, the court’s nine justices seemed largely divided on the prospect of imposing an outright ban on geofence warrants, though they might seek to restrict how such warrants are utilized.

Orin Kerr, a law professor at the University of California, Berkeley, specializing in Fourth Amendment law, stated in a detailed social media post that the court was “likely to dismiss” Chatrie’s claims regarding the legality of the warrant, and would likely permit law enforcement to continue utilizing geofence warrants, provided they are confined in scope.

Cathy Gellis, an attorney writing at Techdirt, remarked in a post that it seemed the court “supports geofence warrants but may hesitate to completely eliminate them.” Gellis’ analysis expected “incremental steps, not sweeping changes” in the court’s ultimate ruling.

Although the case predominantly addresses a search of Google’s location databases, the consequences extend far beyond Google and affect any entity that collects and retains location data. Google eventually transitioned to storing its users’ location information on their devices rather than on its servers, where law enforcement could request access. The company ceased responding to geofence warrant inquiries last year as a direct consequence, according to The New York Times.

The same cannot be said for other tech entities that retain their customers’ location data on their servers, easily accessible to law enforcement. Microsoft, Yahoo, Uber, Snap, and others have previously received geofence warrants.