The Supreme Court has agreed to determine the legality of a new type of warrant: the geofence warrant.[i]  A geofence warrant allows law enforcement to identify which cellphones were in a particular area at the time of a particular crime.[ii] For example, police have issued geofence warrants to determine which phones were within a certain radius of a water drain where a dead body was found, near a United States Postal Service truck that was robbed, and near the scene of smashed car windows during protests.[iii]  Generally, the warrant will be issued to a private third-party, such as Google, to hand over a specific category of data called “Location History,” which is a user-consented type of data collected to “record . . . movements and travels.”[iv]

However, the identity of such users is not automatically available to law enforcement.  Google developed a three-step process of data filtering that must be followed in order for personal identity to be disclosed.[v]  The first set of data that officers are presented with include an “anonymized device ID” for every single phone in its system that was present at the location and date specified by the warrant.[vi] Then, after this list is narrowed down to relevant IDs, Google hands over geographical data for the remaining devices beyond the scope of the warrant.[vii]  Finally, from those left over, law enforcement is able to reveal the names and email addresses of the users associated with the IDs.[viii]  The constitutionality of these warrants has been debated since their inception.  The emergence of new investigative technologies used in law enforcement has likewise intensified Fourth Amendment privacy concerns.[ix]

The Supreme Court has decided to weigh in on this debate after conflicting opinions issued from the U.S. Courts of Appeals for the Fifth Circuit in United States v. Smith and the Fourth Circuit in United States v. Chatrie.[x]  Granting certiorari only in Chatrie, the Court has limited arguments to address solely the question of “whether the execution of [a] geofence warrant violate[s] the Fourth Amendment.”[xi]  At issue in Chatrie is a geofence warrant issued during investigation of a bank robbery in Virginia.[xii]  Petitioner was identified as a suspect and arrested after a warrant was executed—using the process outlined above—for the surrounding 150-meter radius of the bank, covering a two-hour window on the day of the robbery.[xiii]

The lower court decisions are not particularly helpful in predicting the Court’s ultimate disposition in this case.  The district court denied Petitioner’s motion to suppress while avoiding the core question of the geofence warrant’s validity, instead declaring police actions based on the “good-faith exception” that law enforcement relied on warrant approval for a new form of technology.[xiv]  The fourth circuit then affirmed this decision in a one-sentence unexplained per curium opinion.[xv]

The Fourth Amendment prohibits “unreasonable searches and seizures” by the government.[xvi]  While the many intricacies of this phrase are beyond the scope of this article, a “search” within the meaning of the Fourth Amendment generally does not occur unless there is a “reasonable expectation of privacy” being infringed upon.[xvii]  The applicable principle here is referred to as the third-party doctrine, which states that a reasonable expectation of privacy does not exist when a party “takes the risk” and conveys information to a third-party.[xviii]

The use of a data recording device, called a pen register, to track the outgoing phone numbers dialed from a device falls into this category.[xix]  Because most phone users realize that the numbers they call are being conveyed to the telephone company, it is unreasonable to “harbor any general expectation that . . . they . . . will remain secret.”[xx]  However, the third-party doctrine does not extend to Cell Site Location Information (CSLI), which conveys to phone companies a cell phone’s precise location each time it connects to a cell tower, sharing “many of the qualities” as traditional GPS and allowing “near perfect surveillance, as if [the government] had attached an ankle monitor to the phone’s user.”[xxi]

The Court will decide which of these two buckets geofence warrants fit into. Location History could be considered non-intrusive phone records like using a pen register, or pervasive intimate information like CSLI. Understandably, federal courts have had difficulty applying long-standing Fourth Amendment principles to modern investigative technology.[xxii]   The third-party doctrine is a settled, yet relatively underdeveloped principle with its contemporary scope and limits unclear. Currently, it seems the key difference between data that is protected under the Fourth Amendment versus data that is not hinges on the user’s degree of voluntariness to consent to sharing that data and its importance to “participat[ing] in modern life.”[xxiii]  With oral argument in Chatrie set for the end of April,[xxiv] the Court seems to be ready to take advantage of its opportunity to further flesh out the scope of the third-party doctrine and its implications in the contemporary age of ever-growing private data collection.

[i] See Order Granting Certiorari, Chatrie v. United States, No. 25-112 (Jan. 16th, 2026), 2026 U.S. LEXIS 705, at *1; see also United States v. Chatrie, 136 F.4th 100, 101 (4th Cir. 2025) (en banc) (Diaz, C.J., concurring) (describing the geofence warrant as “a novel and powerful technology”).

[ii] See Peter G. Barris & Clay Wild, Cong. Rsch. Serv., LSB11274, Geofence Warrants and the Fourth Amendment 1 (2026).

[iii] See State v. Contreras-Sanches, 5 N.W.3d 151, 156 (Min. Ct. App. 2024); see also United States v. Smith, 110 F.4th 817, 820–21 (5th Cir. 2024); see also Haley Amster & Brett Diehl, Against Geofences, 74 Stan. L. Rev. 385, 396 (2022).

[iv] See Cong. Rsch. Serv., supra note ii, at 3; see generally United States v. Chatrie, 136 F.4th 100, 101 (4th Cir. 2025) (en banc) (C.J. Diaz, concurring) (explaining the process of a geofence warrant and the type of data collected).

[v] See Smith, 110 F.4th at 824.

[vi] See id. at 824–25.

[vii] See id. at 825.

[viii] See id.

[ix] See Cong. Rsch. Serv., supra note ii, at 1.

[x] See id. at 3.

[xi] See Petition for a Writ of Certiorari at i, Chatrie v, United States, No. 25-112 (July 28, 2025); see also Order Granting Certiorari, Chatrie, 2026 U.S. LEXIS 705, at *1.

[xii] See United States v. Chatrie, 590 F. Supp. 3d 901, 905 (E.D. Va. 2022).

[xiii] See United States v. Chatrie, 136 F.4th 100, 101 (4th Cir. 2025) (en banc) (Diaz, C.J., concurring).

[xiv] See Chatrie, 590 F. Supp 3d at 925, 937.

[xv] See Chatrie, 136 F.4th at 101.

[xvi] See U.S. Const. amend. IV.

[xvii] See Katz v. United States, 389 U.S. 347, 360–62 (1967) (Harlan, J., concurring).

[xviii] See Smith v. Maryland, 442 U.S. 735, 743–49 (1979); see also United States v. Miller, 425 U.S. 435, 443 (1976); see also United States v. Trader, 981 F.3d 961, 967 (11th Cir. 2020).

[xix] See Smith, 442 U.S. at 745–46.

[xx] See id. at 743.

[xxi] See Carpenter v. United States, 585 U.S. 296, 311–12 (2018).

[xxii] See id. at 309; see also United States v. Chatrie, 590 F. Supp. 3d 901, 905 (E.D. Va. 2022) (“This case implicates the next phase in the courts’ ongoing efforts to apply the tenets underlying the Fourth Amendment to previously unimaginable investigatory methods.”); see also United States v. Jones, 565 U.S. 400, 417 (2012) (Sotomayor, J., concurring) (referring to the third-party doctrine as “ill suited for the digital age”).

[xxiii] See Orin Kerr, The Fourth Amendment and Geofence Warrants: A Critical Look at United States v. Chatrie, Lawfare (Mar. 12. 2022, at 3:34 PM), https://www.lawfaremedia.org/article/fourth-amendment-and-geofence-warrants-critical-look-united-states-v-chatrie [https://perma.cc/7AEA-UT5X].

[xxiv] See Amy Howe, Supreme Court Announces Cases it Will Hear at Term’s End, SCOTUSBlog (Feb. 11, 2026), https://www.scotusblog.com/2026/02/supreme-court-announces-cases-it-will-hear-at-terms-end/ [https://perma.cc/HBD4-BHYM].