Suspicionless Search: Geofence Warrants and the Fourth Amendment

31 Pages Posted: 27 Apr 2021 Last revised: 13 Feb 2023

Date Written: August 5, 2021


Geofence search warrants, also known as reverse location search warrants, are a new, digital version of the general warrants, or “writs of assistance”, that were at the heart of the Fourth Amendment’s inclusion in the Bill of Rights. Fourth Amendment jurisprudence has been consistently challenged for over a century in the face of technology advancements such as the wiretap, computers, the internet, and mobile phones. But the challenge posed by geofence warrants, in which the government can demand that private sector technology providers disclose a list of mobile devices in a defined place at a defined time, may be the Fourth Amendment’s most vexing encounter yet. When combined with protections provided by the Stored Communications Act, enacted in 1986, it positions the courts as a porous last line of defense between government intrusion and expectations of privacy in the mobile device era.

This Article explains why this situation is perilous, and describes the widening gap between existing Fourth Amendment jurisprudence and rapidly advancing technology to obtain, aggregate, and correlate data about citizens, both anonymous and uniquely identifying, to surveil and profile the public, with a focus on geofence warrants as this era’s emblematic investigative tool. This Article will explain why anonymization is a weak safeguard and argue for more stringent requirements to bring judicial domain knowledge in line with that of law enforcement officers, who have greater access to specialized training in digital forensics. Lastly, the Article will discuss needed reforms to current statutory protections that no longer possess the ability to constrain government intrusion into our daily lives. The judiciary and legislatures place checks on one another, but both are quickly being left behind by technology advances, big data, and private sector inclusion in modern law enforcement.

Keywords: Privacy; Fourth Amendment, ECPA; SCA; big data policing; general search; Constitution

JEL Classification: K14, Z18

Suggested Citation

O'Brien, Tim, Suspicionless Search: Geofence Warrants and the Fourth Amendment (August 5, 2021). Available at SSRN: or

Tim O'Brien (Contact Author)

Master of Jurisprudence ( email )

William H. Gates Hall
Box 353020
Seattle, WA 98105-3020
United States

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