In the landmark 2018 case Carpenter v. United States, the U.S. Supreme Court grappled with what it termed the “new phenomenon” of law enforcement’s ability to “chronicle a person’s past movements through the record of his cell phone signals.”1 At issue in Carpenter was cell-site location information (CSLI), a form of individualized location data generated when mobile phones connect to nearby cell towers. In holding that law enforcement’s acquisition of a suspect’s CSLI was a “search” entitled to Fourth Amendment protection, the Supreme Court recognized that “the progress of science has afforded law enforcement a powerful new tool to carry out its important responsibilities.”2 The Court nevertheless recognized the dangers of unfettered government access to individuals’ “deeply revealing” location information—access “the Framers, ‘after consulting the lessons of history,’ drafted the Fourth Amendment to prevent.”3
Nearly eight years later, the “progress of science” has continued, and the surveillance technology described in Carpenter now seems almost quaint. The Supreme Court recently granted certiorari in United States v. Chatrie, a case arising from the Fourth Circuit that centers on so-called “geofence” technology. A geofence is a virtual geographic boundary, and geofence warrants authorize law enforcement to collect and search the location data of all devices present within a geofence during a specified timeframe. Location data obtained via a geofence warrant is significantly more precise than CLSI, and it is “remarkably extensive.”4 “If a device is in a building, for example, its Location History can show on which floor.”5
Many geofence warrants, including the one at issue in Chatrie, are served on Google. Google is a frequent target of geofence warrants because, as the district court in Chatrie observed, its “services function across Apple and Android devices,” and because its trove of location data—which includes data on “numerous tens of millions” of users—is “sweeping, granular, and comprehensive.”6
Chatrie arose from a 2019 bank robbery that proved difficult to solve. Hoping to identify a suspect, law enforcement applied for a geofence warrant seeking location data for every device associated with a Google account within a 150-meter radius of the bank within the hour surrounding the crime. Pursuant to the three-step process Google had previously developed to respond to geofence warrants, law enforcement first received anonymized location data for all devices that fell within the warrant’s geographic and temporal limits. At the second step, investigators narrowed the pool of accounts and requested expanded location information for those selected accounts, covering a broader, two-hour period. At the third step, after reviewing the expanded data, investigators further refined the list to three specific accounts. Google then disclosed identifying subscriber information for those accounts, ultimately linking one of them to defendant Okello Chatrie.
Chatrie moved to suppress the location data that led to his arrest. The district court agreed with Chatrie that the geofence warrant violated the Fourth Amendment, concluding that “the government lacked particularized probable cause as to every Google user in the geofence,” which “covered 70,686 square meters of land … in a busy part of the Richmond metro area.”7 Nevertheless, the district court denied suppression pursuant to the “good faith” exception to the Fourth Amendment’s exclusionary rule—a doctrine permitting the admission of unlawfully obtained evidence when law enforcement acts under a good faith belief that their actions are lawful.
Chatrie was convicted, and he appealed the denial of his suppression motion to the Fourth Circuit. A divided three-judge panel affirmed, but on markedly different grounds. In a 2-1 decision authored by Judge Richardson, the panel concluded that the geofence warrant was not a “search” within the meaning of the Fourth Amendment because: (1) individuals have no reasonable expectation of privacy in two hours’ worth of location data; and (2) even if they do, Chatrie “voluntarily exposed his location information to Google by opting in to Location History” on his cell phone.8 For these reasons, the panel concluded that the geofence warrant did not run afoul of the Fourth Amendment at all.
Exactly one month after the panel decision in Chatrie, the Fifth Circuit handed down its own geofence decision in United States v. Smith.9 Like Chatrie, Smith involved a geofence warrant served on Google, but the Fifth Circuit viewed the constitutional questions differently. Responding directly to Fourth Circuit panel’s reasoning, the Fifth Circuit emphasized that “the potential intrusiveness of even a snapshot of precise location data should not be understated.”10 As for a user’s decision to “opt-in” to Google’s location tracking, the Fifth Circuit observed that, “[a]s anyone with a smartphone can attest, electronic opt-in processes are hardly informed and, in many instances, may not even be voluntary.”11 A user’s ability to “opt out”—which companies like Google make difficult to do—did not, in the Fifth Circuit’s view, eliminate Fourth Amendment protections.
The Fifth Circuit in Smith went further still, analogizing geofence warrants to “general warrants,” which “present the exact sort of ‘general, exploratory rummaging’ that the Fourth Amendment was designed to prevent.”12 The court therefore held that geofence warrants are categorically unconstitutional. Even so, the Fifth Circuit—like the district court in Chatrie—affirmed the denial of suppression under the good faith exception.
Several months later (and perhaps in part because of Smith), the Fourth Circuit granted rehearing en banc in Chatrie. The en banc court issued a one-sentence per curiam affirmance accompanied by nine separate opinions—eight concurrences (with varying groups of judges joining the concurring opinions) and one dissent—revealing deep disagreement on the court over how the Fourth Amendment should apply to geofence warrants. Chief Judge Diaz and Judge Heytens preferred resolving Chatrie narrowly under the good-faith exception, declining to reach the constitutional question. Judges Wilkinson, Niemeyer, King, and Richardson concluded that no Fourth Amendment search occurred at all. By contrast, Judges Wynn and Berner found that the geofence warrant did constitute a search, though they agreed suppression was unwarranted because law enforcement acted in good faith. In dissent, Judge Gregory explained that not only did he believe geofence warrants to be unconstitutional, but also that he would refuse to apply the good-faith exception and would grant suppression.
Chatrie now arrives at the Supreme Court, which granted certiorari to address the constitutional issue that split the Fourth and Fifth Circuits. It is difficult to predict the outcome; little is certain except that geofence warrants have become the latest flashpoint in Fourth Amendment law. There are no easy answers when applying centuries-old constitutional principles to rapidly evolving technologies. A decision invalidating geofence warrants across the board could, as Judge Wilkinson warns, “frustrate law enforcement’s ability to keep pace with tech-savvy criminals.”13 Yet, as Judge Ho observed in Smith, “hamstringing the government is the whole point of our Constitution. Our Founders recognized that the government will not always be comprised of publicly-spirited officers—and that even good faith actors can be overcome by the zealous pursuit of legitimate public interests.”14
As in Carpenter, the Justices must navigate these competing interests in deciding how much privacy individuals may reasonably expect in a world increasingly capable of tracking their movements with remarkable precision and ease. The Court must also weigh the constitutional significance of users’ voluntary participation in digital ecosystems that collect and store their location data. In Carpenter, the Supreme Court reasoned that because cell phones are “indispensable to participation in modern society,” a person does not relinquish an expectation of privacy in her location data merely by carrying one.15 The Court must now consider whether to treat similarly the additional step of opting into (or not opting out of) location tracking.
For Chatrie himself, relatively little is at stake. The Court declined to review the applicability of the good faith exception, virtually ensuring that his conviction will stand. For the rest of us, however, the case may define the boundaries of digital privacy for years to come—or at least until the next, even more powerful technology makes its way to the Court.
1Carpenter v. United States, 585 U.S. 296, 309 (2018).
2Id. at 320.
3Id. (quoting United States v. Di Re, 332 U.S. 581, 595 (1948)).
4United States v. Chatrie, 136 F.4th 100, 102 (4th Cir. 2025) (Diaz, J., concurring).
5Id.
6United States v. Chatrie, 590 F. Supp. 3d 901, 907 (E.D. Va. 2022).
7United States v. Chatrie, 590 F. Supp. 3d 901, 925 (E.D. Va. 2022) (cleaned up).
8United States v. Chatrie, 107 F.4th 319, 331 (4th Cir. 2024).
9United States v. Smith, 110 F.4th 817 (5th Cir. 2024).
10Id. at 833.
11Id. at 835.
12Id. at 837 (5th Cir. 2024) (quoting Coolidge v. New Hampshire, 403 U.S. 443, 467 (1971)).
13United States v. Chatrie, 136 F.4th 100, 110 (4th Cir. 2025) (Wilkinson, J., concurring).
14United States v. Smith, 110 F.4th 817, 841 (5th Cir. 2024) (Ho, J., concurring).
15Carpenter, 585 U.S. at 315.