Chatrie v. United States: The Supreme Court Brings Geofence Warrants Under the Fourth Amendment

On June 29, 2026, the United States Supreme Court held in Chatrie v. United States that a geofence warrant is a search under the Fourth Amendment. The decision came down 6 to 3, with Justice Kagan writing for the majority. It is the most important digital privacy ruling since Carpenter v. United States in 2018, and it lands on ground Massachusetts courts prepared years ago.

What a Geofence Warrant Is

A geofence warrant works backwards. Instead of identifying a suspect and asking where his phone was, police draw a box around a crime scene and ask a provider, usually Google, to identify every device inside the box during a window of time. The technique searches the location histories of everyone who passed through, almost all of them innocent, in the hope that one of them is the suspect. The Chatrie case began with a Virginia bank robbery and a warrant that swept the location data of every Google user near the bank.

What the Court Held

The majority held that people keep a reasonable expectation of privacy in their cellphone location data, and that a government demand for it intrudes on a constitutionally protected interest even when the window is short and the data sits with a third party. The Court rejected the government’s argument that users voluntarily share this data, describing it instead as the automatic price of carrying a phone. That reasoning extends Carpenter, which reached the same conclusion for historical cell site location information, and it continues the retreat from the old third-party doctrine in digital cases. The Court sent the case back for a ruling on whether this particular warrant satisfied probable cause and particularity, so the fight now moves to how narrow these warrants must be.

Massachusetts Was Already There

For Massachusetts defendants, Chatrie confirms a direction our courts chose first. The Supreme Judicial Court held in Commonwealth v. Augustine, 467 Mass. 230 (2014), four years before Carpenter, that police need a warrant for historical cell site location data under Article 14 of the Massachusetts Declaration of Rights. Commonwealth v. McCarthy, 484 Mass. 493 (2020), applied mosaic reasoning to automatic license plate readers, and Commonwealth v. Mora, 485 Mass. 360 (2020), required a warrant for long-term pole camera surveillance of a home. Our pages on phone, computer, and digital device searches and illegal searches and seizures explain how Article 14 routinely protects more than the federal floor. Chatrie raises that floor.

What It Means for Massachusetts Cases

Any Massachusetts case built on a geofence return now has a suppression issue worth litigating. The warrant must rest on probable cause and must describe the place to be searched with particularity, and a box drawn around a busy block for an open-ended window will struggle on both fronts. The same logic reaches reverse keyword warrants and tower dumps, techniques that also search everyone to find someone. Defense counsel should demand the full warrant package in discovery, map the geofence against the probable cause actually alleged, and move to suppress where the sweep outruns the showing. The framework is laid out in our post on digital search warrants in Massachusetts and in the digital search FAQs. Location data questions in car cases are covered in our guide to the modern Massachusetts traffic stop.

The Longer Arc, and Why Timing Matters

Chatrie is best understood as the fourth step in a line the Court has been walking for fifteen years. United States v. Jones, 565 U.S. 400 (2012), held that attaching a GPS tracker to a car is a search. Riley v. California, 573 U.S. 373 (2014), required a warrant to search a phone seized at arrest and recognized that digital devices hold the privacies of life. Carpenter then refused to let the government use the old third-party doctrine of Smith v. Maryland and United States v. Miller to grab week-long location histories without a warrant. Chatrie completes the thought. If the government cannot demand your location history by name without a warrant, it cannot avoid the problem by demanding everyone’s location history by place.

Timing matters because new Fourth Amendment rules apply to every case still pending on direct review. A defendant whose case involves a geofence return, a tower dump, or a reverse keyword demand can raise Chatrie today, and counsel should be filing preservation letters for the underlying returns before providers purge them. Massachusetts already requires a warrant when police cause a phone to reveal its real-time location under Commonwealth v. Almonor, 482 Mass. 35 (2019), and the combination of Chatrie and Article 14 gives Massachusetts defendants two independent bodies of law to litigate under. When the suppression motion wins, the fruit of the poisonous tree doctrine reaches everything the return produced, which in a geofence case is often the identification itself.

Who Geofence Cases Actually Reach

Geofence returns do not select for guilt. They select for proximity, and in Boston and Cambridge proximity means students and young professionals. A box drawn around a late-night incident near a campus, a stadium, or a nightlife block sweeps in every phone in the crowd, and the person contacted weeks later is often a college or university student with no idea why police are calling. The right response is silence and a lawyer, as our guides on the right to remain silent and the first 24 hours after an arrest explain. For a licensed professional or anyone whose career runs on background checks, the arraignment itself is the injury, which makes the suppression fight and the pre-arraignment posture of these cases worth everything. Where the case begins with a complaint application instead of an arrest, the clerk-magistrate hearing is the place to attack a thin geofence identification before any record exists.

Serpa Law Office litigates digital search issues across Massachusetts. If your case involves location data, a device search, or any warrant you have not seen, contact Serpa Law Office at 617.936.0201 for a confidential consultation.