Civil-rights groups ask Ninth Circuit to bar 'tower-dump' warrants in test of reverse-location searches

Civil-liberties groups on Tuesday asked the U.S. Court of Appeals for the Ninth Circuit to declare so-called tower-dump warrants unconstitutional, setting up a closely watched test of how far courts will go in limiting reverse-location searches after the Supreme Court’s June ruling on geofence warrants.

The American Civil Liberties Union, ACLU of Nevada and Electronic Frontier Foundation filed an amicus brief in United States v. Spurlock, No. 26-689, supporting defendant-appellant Cory Spurlock. The groups urged the Ninth Circuit to hold that tower-dump warrants are general warrants barred by the Fourth Amendment, or at least to sharply restrict how they are used.

Tower dumps are a type of reverse-location search. Instead of starting with a suspect, investigators start with a place and time and compel a wireless carrier to disclose records for all devices that connected to specified cell towers or sectors during that window. Like geofence warrants, they can sweep in data from many people who are not suspected of any crime.

That is why the case matters beyond one prosecution. A Ninth Circuit ruling could shape the use of tower dumps across the western U.S., where police and prosecutors would have to adjust to whatever constitutional limits the court sets.

The warrant at issue grew out of an investigation into two murder victims found on the side of a rural California highway. Police also found a car belonging to one of the victims several miles away on the same highway. According to the district court record, Mono County Sheriff’s Office Sgt. Magdeleno Hernandez applied on Nov. 13, 2020, for records tied to two geographic points on U.S. Highway 395 for the evening of Nov. 8, 2020, during a time window described as 5 p.m. to 11 p.m.

The district court said the warrant, identified in the record as 20-SW-56, captured private data belonging to 1,686 users. Only Verizon produced records in response, the court said. Investigator Pelichowski then manually reviewed the Verizon return and used numbers from the tower dump to develop additional leads and seek further warrants. Some of that later evidence implicated Spurlock.

In an April 11, 2025, ruling in the U.S. District Court for the District of Nevada, U.S. District Judge Miranda M. Du concluded that the search violated the Fourth Amendment. “As to the motion to suppress regarding the tower dump, the Court finds that a tower dump is a search and the warrant law enforcement used to get it is a general warrant forbidden under the Fourth Amendment,” Du wrote.

But Du denied suppression, finding that investigators had relied on the warrant in good faith. That left the evidence in the case despite her conclusion that the warrant itself was unconstitutional.

The new amicus brief asks the Ninth Circuit not to stop there. The groups argued the appeals court should decide the constitutional question directly instead of resolving the case solely through the good-faith exception to the exclusionary rule. They urged the court to reverse and suppress the evidence obtained from the warrant.

The brief says tower dumps recreate the core problem the Fourth Amendment was meant to prevent: broad searches untethered to individualized suspicion. “Searching all people in an area without probable cause to believe they were all involved in the criminal activity under investigation reproduces the evils of general warrants and is not constitutionally permitted,” the amici wrote.

If the Ninth Circuit declines to impose a categorical ban, the groups asked it to require strict limits, including narrow bounds on the search’s scope and duration, notice to affected people, and minimization or deletion of irrelevant data.

The case arrives as courts sort out the implications of recent Supreme Court decisions on digital location tracking. In Carpenter v. United States in 2018, the high court held that historical cell-site location information can receive Fourth Amendment protection. Then, on June 29, 2026, the court held in Chatrie v. United States that geofence warrants are searches under the Fourth Amendment, while leaving lower courts to work through whether particular warrants satisfy probable-cause and particularity requirements.

Du’s ruling in Spurlock also relied in part on the Fifth Circuit’s 2024 decision in United States v. Smith, which said the geofence warrants in that case were categorically prohibited general warrants, though that court also applied the good-faith exception.

Now the Ninth Circuit is being asked to decide whether the same constitutional limits that increasingly govern geofence requests should also bar, or tightly constrain, tower dumps that collect location-linked records from large numbers of bystanders.