We’re Asking the Ninth Circuit to Hold Reverse Location Warrants Categorically Unconstitutional

Yesterday, along with the ACLU, EFF filed an amicus brief in the Ninth Circuit court of appeals in United States v. Spurlock, a case involving a “tower dump” warrant. These overbroad warrants require cellular providers to turn over location data about every phone in a given area at a given time. This is the first such case to be heard by a federal appeals court since the US Supreme Court ruled this summer that highly similar “geofence” warrants are searches under the meaning of the Fourth Amendment.

Spurlock involves an investigation into two murder victims discovered 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. They quickly sought a tower dump warrant for an area covering this stretch of road, which eventually revealed location data on nearly 1,700 unique phones. Faced with a motion to suppress, the district court relied on a Fifth Circuit court of appeals decision about geofence warrants to hold that tower dumps are similarly categorically unconstitutional “general warrants” that violate the Fourth Amendment. However, the court refused to suppress evidence on the basis of the “good faith doctrine.”

Our amicus brief on appeal makes several key arguments.

First, we point out that the Supreme Court’s decision in the geofence case Chatrie v. United States this summer only strengthens the arguments that tower dumps are unconstitutional general warrants. Tower dumps are a somewhat older technique than geofence warrants, but they are both “reverse location searches,” in which police “tap into an all-encompassing database, allowing them to undertake nearly perfect, retrospective surveillance of countless persons and places.” This is the sort of untargeted “general warrant” the framers of the Fourth Amendment wanted to prevent. As we write in the brief, “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.” It’s this rule of law that prevents police from searching the houses of a hundred, or even a thousand people in the vicinity of a crime.

Second, we note that even if high courts continue to allow tower dump and geofence warrants in any cases, core Fourth Amendment law requires strict limits to protect the privacy of innocent bystanders, including limits on the scope and duration of the warrants, as well notice to affected individuals and after-the-fact deletion and minimization of irrelevant data.

Finally, we argue that the Fourth Amendment requires the court to set aside the good faith doctrine in cases like these and actually decide the constitutional issue. Too often courts pass the buck in cases involving novel surveillance techniques, leading to situations where police can continue using the technique for years or even decades without a definitive ruling.