The University of New Hampshire Law Review
Abstract
Geofencing, a location-based investigative technique that uses digital mapping to identify individuals within a defined geographic area, has become an increasingly common yet constitutionally contentious tool for law enforcement. Federal courts remain deeply divided on whether geofence warrants comport with the Fourth Amendment. The Fifth Circuit has held that such warrants constitute unconstitutional general warrants, while the Fourth Circuit has concluded that they do not even amount to searches under the third-party doctrine. This circuit split exposes a broader tension between technological innovation and foundational constitutional privacy protections.
This Article argues that geofence warrants should be treated as searches subject to heightened scrutiny. Drawing on Carpenter v. United States, it contends that individuals maintain a reasonable expectation of privacy in their physical movements as captured through GPS data. To prevent the expansive discretion and overbreadth characteristic of general warrants, this Article proposes a tripartite standard requiring that geofence warrants be limited to the scope of probable cause, confined to a narrow temporal window, and restricted to a geographic area closely tied to the alleged crime.
The Article further proposes a sliding-scale reasonableness test that incorporates both traditional Fourth Amendment balancing and the factors articulated in Carpenter, emphasizing the sensitivity, volume, and voluntariness of disclosed data. Finally, it urges a presumptive limitation on the third-party doctrine’s applicability to geofence data except where the warrant’s scope is narrowly circumscribed. Together, these principles safeguard individual privacy while preserving legitimate investigative needs in the digital age.
Repository Citation
Mathias Lang, The Fourth Amendment and Geofence Warrants: Safeguarding Geofencing's Constitutionality Through Particularity and Reasonableness, 24 U.N.H. L. Rev. 509 (2026).