While the court battle between Elon Musk and OpenAI may draw more eyes Monday, another case getting underway could carry far broader implications for personal freedom. The Supreme Court is scheduled to hear arguments in a case that will determine the legality of geofencing, a technique law enforcement uses to mine location history data to identify who was near the scene of a crime and may have been involved. Geofencing, in essence, draws a virtual perimeter around a crime scene. The government then obtains a warrant requiring tech companies to search their location data for anyone within that area during the relevant time frame. In this case, Google’s location history data was used to identify the person ultimately convicted. Opponents argue the process violates the Fourth Amendment , which protects against unreasonable government searches and seizures. In an increasingly digital world, however, the amendment’s boundaries have become murkier. “Geofence warrants are an unprecedented increase in the government’s ability to locate individuals without substantial investigation or investment of resources,” writes the National Association of Criminal Defense Lawyers in a statement. “[They] are general warrants — which are prohibited by the Fourth Amendment—because they are devoid of probable cause and particularity.” United States v. Chatrie The case at the center of Monday’s hearing is U.S. v. Chatrie. Okello Chatrie is currently serving a 12-year prison sentence for robbing a credit union near Richmond, Va. Police used a geofence warrant to identify him, which his legal team argues was unconstitutional. The Fourth Circuit U.S. District Court disagreed. Around the same time, however, a similar case before the Fifth Circuit reached the opposite conclusion, finding that people have a reasonable expectation of privacy in location history data. Both cases centered on Google location history. Those conflicting rulings sent the case to the Supreme Court, which will now weigh the extent to which “the execution of [a] geofence warrant violate[s] the Fourth Amendment.” “The Fourth Circuit held that a geofence warrant yielding two hours’ worth of precise location data involves no Fourth Amendment search and thus need not be supported by probable cause,” writes the Harvard Law Review . “The Fifth Circuit held not only that the practice constitutes a Fourth Amendment search but also that, given the massive scale of the database at issue, the Fourth Amendment does not countenance geofence warrants at all, notwithstanding probable cause that evidence would be found in the searched records.” The government is expected to argue that because cell phone users voluntarily opted into location history tracking, they waived any reasonable expectation of privacy. Chatrie’s team, meanwhile, is expected to argue that not only was a warrant required, but that the geofence warrant itself was overly broad, amounting to an unreasonable search of large numbers of innocent people. Limits already underway Privacy advocates are siding with Chatrie. Google, for its part, has already moved to limit geofencing’s reach. Historically, the company stored users’ location history data on cloud servers. Last July, however, it shifted that data onto individual devices, reducing its own ability to identify users’ past locations. Not all tech companies have followed suit, however, which keeps the case highly relevant. The broader concern is that geofencing can sweep innocent people into criminal investigations while also enabling large-scale surveillance. At the same time, the practice has proved useful to investigators. Many arrests following the Jan. 6 Capitol riot, for instance, relied on geofencing data. It remains unclear how extensively law enforcement relies on geofence warrants. The latest available data comes from 2020, when authorities served Google with 11,500 such warrants, writes Hofstra Law Review . Several states, meanwhile, have enacted laws restricting geofencing, particularly around healthcare facilities in abortion-related investigations. The ruling could also extend beyond geofence warrants themselves. Legal experts say it may shape the future legality of other digital investigative tools, including reverse-keyword warrants and chatbot data requests. A decision is expected sometime this summer.