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

Yesterday, the Electronic Frontier Foundation (EFF) and the American Civil Liberties Union (ACLU) jointly submitted an amicus brief to the Ninth Circuit Court of Appeals in the United States v. Spurlock case. This case centers around a controversial "tower dump" warrant, which requires cellular providers to disclose location data for every phone within a specified area at a specific time.

This is the first such case to be heard by a federal appeals court since the U.S. Supreme Court ruled last summer that similar "geofence" warrants are considered searches under the Fourth Amendment. The Spurlock case involves the investigation of two murder victims found on a rural California highway. Police obtained a tower dump warrant for an area covering the highway stretch where the victims were found, which subsequently revealed location data from nearly 1,700 unique phones.

In their brief, EFF and the ACLU make several crucial arguments. They first emphasize that the Supreme Court's decision in the geofence case this summer only reinforces the idea that tower dumps are also categorically unconstitutional "general warrants" that violate the Fourth Amendment. Both tower dumps and geofence warrants are considered "reverse location searches," in which police exploit an extensive database to conduct extensive surveillance on multiple individuals and locations without probable cause to believe they were involved in the criminal activity.

The EFF and ACLU argue that this untargeted surveillance is akin to the general warrants that the framers of the Fourth Amendment sought to avoid and is not constitutionally permissible.

Secondly, the brief highlights that, even if high courts continue to permit tower dump and geofence warrants in other cases, core Fourth Amendment principles demand stringent limitations to safeguard the privacy of innocent bystanders. These limitations include restricting the scope and duration of the warrants, providing notice to affected individuals, and ensuring the deletion and minimization of irrelevant data after the fact.

Finally, EFF and ACLU argue that the Fourth Amendment requires the court to disregard the "good faith doctrine" and address the constitutional issue directly. Often, courts simply defer to law enforcement in cases involving new surveillance techniques, leading to continued use of these methods for years or even decades without a definitive ruling.