A cell site tower dump to see who was there at the time of the crime is governed by Carpenter, but the law is completely unclear and the good faith exception saves it. United States v. McDonald, 2026 U.S. Dist. LEXIS 5169 (D. Mass. Jan. 12, 2026):
No circuit court of appeals has decided the issue. The Seventh Circuit has rejected a defendant’s contention that Carpenter resolved the question but has not squarely held that tower dumps do not constitute Fourth Amendment searches. See United States v. Adkinson, 916 F.3d 605, 610-11 (7th Cir. 2019) (per curiam). Similarly, the Eighth Circuit has declined to resolve the question. See United States v. James, 3 F.4th 1102, 1106 n.3 (8th Cir. 2021). The Fifth Circuit and certain judges of the Fourth Circuit have espoused competing views with respect to geofencing, a similar but distinct technology from tower dumps. Compare United States v. Smith, 110 F.4th 817, 830-36 (5th Cir. 2024) (holding that geofencing constitutes a Fourth Amendment search), cert. denied, No. 24-7237, 2025 WL 3131804 (U.S. Nov. 10, 2025), with United States v. Chatrie, 136 F.4th 100 (4th Cir. 2025) (affirming district court judgment in geofencing case with no controlling opinion), petition for cert. filed, No. 25-112 (U.S. July 28, 2025).
The issue is a close call. This Court concludes that the courts that have held that tower dumps constitute a Fourth Amendment search have the stronger argument. The Court finds Medina’s in-depth discussion of this issue persuasive, see 712 F. Supp. 3d at 236-46, and briefly highlights the two primary bases for the conclusion that search warrants are required to execute tower dumps.
First, although tower dumps typically seek CSLI over a shorter duration of time than the longer-term individual CSLI at issue in Carpenter, the same privacy interests are implicated. Tower dumps seek “time-stamped data [that] provides an intimate window into a person’s life, revealing not only his particular movements, but through them his ‘familial, political, professional, religious, and sexual associations.'” Carpenter, 585 U.S. at 311 (quoting United States v. Jones, 565 U.S. 400, 415 (2012) (Sotomayor, J., concurring)). For example, even though the tower dumps here were executed to identify individuals operating primarily on “public thoroughfares” to commit a crime, they may have also incidentally collected data regarding those individuals’ activities in “private residences, doctor’s offices, political headquarters, and other potentially revealing locales.” Id. And tower dumps, like searches of individualized CSLI, allow law enforcement to “travel back in time to retrace a person’s whereabouts,” even if the identity of that person is not yet known. Id. at 312; see id. at 315 (noting that CSLI provides a “detailed chronicle of a person’s physical presence compiled every day, every moment, over several years”). Critically, regardless of whether the government seeks longer-term individual CSLI or shorter-term tower-dump CSLI, the location data at issue is “detailed, encyclopedic, and effortlessly compiled,” thus implicating the privacy interests of the countless people who “carry cell phones with them all the time.” Id. at 309, 311.
Second, Carpenter’s rationale for declining to apply the third-party doctrine to long-term individual CSLI applies with equal force to tower dumps. Carpenter “recognize[d] that CSLI is an entirely different species of business record” from those usually underpinning the third-party doctrine, such that the fact that CSLI is shared with wireless carriers does not undermine the privacy interests at issue. Id. at 318. And as the Supreme Court noted, “[v]irtually any activity on [a] phone generates CSLI,” effectively forcing individuals to “leav[e] behind a trail of location data.” Id. at 315. For that reason, and because a cell phone is “almost a ‘feature of human anatomy,'” id. at 311 (quoting Riley v. California, 573 U.S. 373, 385 (2014)), users of cell phones cannot reasonably be viewed as voluntarily exposing their location information. These principles are inherent to the “unique nature” of CSLI, id. at 309, whether it is collected through an individualized search or through a tower dump.
