In a significant move to safeguard digital privacy, the **EFF** and **ACLU** have jointly submitted an amicus brief in *United States v. Spurlock*. The case, now before the Ninth Circuit Court of Appeals, scrutinizes the legality of 'tower dump' warrants – a controversial method requiring cellular providers to disclose location data for every phone within a specified area during a particular timeframe. This legal challenge arrives on the heels of a crucial US Supreme Court decision earlier this summer, which determined that similar 'geofence' warrants constitute searches under the Fourth Amendment. The *Spurlock* case could set a precedent for how federal courts handle these expansive surveillance techniques. ### The Case: *United States v. Spurlock* The *Spurlock* investigation began after two murder victims were discovered on a rural California highway, with their vehicle found miles away. Law enforcement subsequently obtained a tower dump warrant covering the relevant stretch of road, which ultimately yielded location data for nearly 1,700 unique phones. Facing a motion to suppress this evidence, the district court referenced a **Fifth Circuit** decision concerning geofence warrants. It concluded that tower dumps are similarly unconstitutional 'general warrants' that violate the Fourth Amendment. However, the court declined to suppress the evidence, citing the 'good faith doctrine.' ### Key Arguments from the Amicus Brief The **EFF** and **ACLU**'s amicus brief presents several critical arguments: #### Strengthening Fourth Amendment Protections First, the brief emphasizes that the Supreme Court's ruling in *Chatrie v. United States* – the geofence warrant case – reinforces the argument against tower dumps. While tower dumps predate geofence warrants, both are 'reverse location searches' that allow police to conduct 'nearly perfect, retrospective surveillance of countless persons and places.' The brief argues this constitutes the kind of untargeted 'general warrant' the Fourth Amendment was designed to prevent. As stated 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." #### Limiting Scope and Protecting Innocent Bystanders Second, the organizations contend that even if high courts permit tower dump and geofence warrants in some instances, the Fourth Amendment mandates strict limitations to protect the privacy of innocent individuals. These limits should encompass the scope and duration of warrants, require notice to affected individuals, and ensure the post-collection deletion and minimization of irrelevant data. #### Challenging the 'Good Faith Doctrine' Finally, the brief argues that the Fourth Amendment necessitates courts to set aside the 'good faith doctrine' in such cases and directly address the constitutional questions. The **EFF** and **ACLU** warn that courts too often sidestep definitive rulings on novel surveillance technologies, enabling law enforcement to continue using them for extended periods without proper judicial review.