(From The Informer, June, 2026 edition; Federal Law Enforcement Training Center)

On May 20, 2019, a man robbed a credit union located in Midlothian, Virginia. Afterward, witnesses told law enforcement that the suspect was using his cell phone prior to entering the credit union. Law enforcement applied for a geofence warrant to Google. A geofence warrant mandates information about any cellular telephones in use in the area around a specified physical location. Various functions on cellular telephones, including applications, can cause a cell phone to be in use and reveal location information as a result.

A United States Magistrate Judge authorized a geofence warrant with a three-step process. In the first step, law enforcement was authorized to receive information about cell phones in use within a 150-meter radius of the credit union, the geofence area, for thirty minutes before and after the robbery. In the second step, law enforcement identified potentially relevant cell phones and were authorized to provide a narrowed list of those cell phone numbers to Google who would provide location information inside and outside the 150-meter radius for a period of two hours before and after the robbery. Lastly, law enforcement looked at the information provided in step two and then narrowed the list down again and was authorized to receive the personal identifiers for the phone number from this smallest list. The defendant was one of the three users on the final list. Location history from Google was provided approximately every two minutes, approximately 720 times a day.

After further investigation, the defendant was charged with robbery and related firearms offenses. The defendant filed a motion to suppress the information obtain via the geofence warrant. The motion to suppress was denied and the district court held that the warrant violated the Fourth Amendment but denied the motion to suppress under the Good Faith exception. The Fourth Circuit Court of Appeals upheld the denial on the theory that no search had occurred because there was no reasonable expectation of privacy (REP) in information that the defendant voluntarily disclosed to Google.

The Supreme Court looked only to the question of whether law enforcement conducted a “search” when it obtained geofence information so as to implicate the Fourth Amendment. In Carpenter v. United States, the Supreme Court ruled that an individual has REP in seven or more days of cell site location information (CSLI). The Court left open whether less than seven days of information would be a “search” for Fourth Amendment purposes. While geofence information is for all users in a geographic area, CSLI information is for a single phone and indicates each time that the cell phone connects to any relevant cell tower.

The Court repeated concerns about personal privacy that it raised in Carpenter and noted that the geofence is even more precise in terms of location accuracy, including that it can show the elevation (i.e., what floor the person is on in a building) of the cell phone user. It also deflected Government arguments that the type and quantity of information is limited in scope and time so there is no Fourth Amendment violation. The Court rejected that argument noting there is not a “Constitution-free zone” for Fourth Amendment intrusions, regardless of the amount of time involved.

The Government also argued that the third-party doctrine covers this information because the user reveals this information to the phone company. The Court noted that to properly use all but the very basics of a cell phone, including applications, users must opt-in to the location history mechanisms of Google.

Last, the Court rejected the Government’s argument that this case should be governed by United States v. Knotts, which found that the use of a beeper (a radio transmitter) in public locations was not a search within the Fourth Amendment. In response, the Court noted the technology there was “rudimentary” and their decision in Knotts even noted the analysis could change with “more sophisticated surveillance.”

Based on the foregoing, the Court found that a geofence is a search for purposes of the Fourth Amendment. The Court touched briefly on the “uncommon multi-step” method utilized in this warrant but ultimately remanded this case to the Court of Appeals to address the legality of that process.

For the Court’s opinion: https://supreme.justia.com/cases/federal/us/609/25-112.