Blue Brief 2025-2026

inapposite. In that case, the government obtained seven days’ worth of historical cell site location information (CSLI) from Carpenter’s provider, using only an administrative order as allowed under the federal Stored Communications Act . In holding that the subpoena violated the Fourth Amendment, the Court identified several features of CSLI data that are clearly applicable to the location data at issue in Chatrie as well. As the Chatrie Court notes, location history provides an even more complete picture of a person’s movements than CSLI data: while the latter periodically tracks pings of the target’s phone off of the nearest cell tower, location history can pinpoint the party’s whereabouts

within 20 meters and even detect which floor of a building they are on. Unlike constitutionally acceptable forms of surveillance, like stakeouts and physical tailing on public streets, both CSLI data and location history allow police to learn a party’s whereabouts retrospectively (rather than in real time) and with very little effort. All of these factors pose a heightened threat to the target’s privacy interests. The government’s best argument in Chatrie was that the duration of the data collection was much shorter than that in Carpenter — only two hours of users’ movements as opposed to a full week. The Court rejected this potential temporal limitation to the reach of Carpenter , noting (while quoting Justice Sotomayor’s earlier concurrence in Jones v. United States ) that “even short-term monitoring of a person’s physical movements can provide a wealth of detail about his familial, political, professional, religious, and sexual associations.” The most important difference between Chatrie and Carpenter implicates the issue the Court left unresolved: in Chatrie , the officers obtained a geofence warrant supported by evidence that a man had robbed a particular credit union at a particular time. If such a warrant is “reasonable,” then the search is constitutional — but that question turns on whether the warrant appropriately established probable cause as to the particular user data searched. The application for the geofence warrant triggered a three-step process. First, Google would produce anonymized location data for all cell phones within the geofence, initially during the one hour around the crime. Second, police would attempt to narrow down the list by reviewing each phone’s coordinates and comparing that against the time and location of the crime. Google would provide still-anonymized data for the narrower list but also include locations

The most clear-cut impact of Chatrie

will be its extension of Carpenter … which recognized the intimacy of the data captured by our devices and the effective involuntariness of both their presence on our persons and the subtle activation of location tracking features within them.

UNIVERSITY OF SAN DIEGO SCHOOL OF LAW | Faculty Review of 2025-2026 U.S. Supreme Court Term | Page 36