The Threat of Geofence Warrants: Why Courts Should Deem Geofence Warrants Unconstitutional Under the Fourth Amendment

by Shirin Asgari*

Circuit courts are currently split on the constitutionality of geofence warrants. Geofence warrants grant law enforcement officers the power to access personal user data collected and stored by tech giants, such as Apple and Google. This Contribution considers the Fourth Amendment implications of geofence warrants and argues that such warrants are unconstitutional. First, given the Supreme Court’s previous reasoning under Carpenter v. United States,¹ individuals have a reasonable expectation of privacy to their location information and other highly personal information attached to their accounts. Second, the nature of geofence warrants makes it impossible to establish probable cause over all individuals whose information is seized and searched beyond mere proximity, in violation of existing Supreme Court precedent established in Ybarra v. Illinois.² Lastly, geofence warrants lack particularity and give law enforcement officers unbridled discretion to search an individual’s information, in clear violation of the Fourth Amendment.

The utilization of geofence warrants by law enforcement raises profound concerns regarding privacy and constitutional rights. Geofence warrants grant law enforcement access to digital records identifying all cell phone users present within a “specified set of places and times, called a ‘geofence,’” usually presented as an anonymized list.³ The Bureau of Alcohol, Tobacco, Firearms and Explosives has issued geofence warrants to scrutinize innocent, law-abiding protestors who attended a Black Lives Matter protest in Kenosha, Wisconsin.⁴ Geofence warrants have also led to the wrongful accusations of individuals like Zachary McCoy, who found himself incurring substantial legal expenses to defend against a burglary charge that location data wrongly implicated him with.⁵ These instances underscore the significant privacy and constitutional concerns arising out of law enforcement’s use of geofence warrants. The growing use of these warrants has sparked intense debate among courts surrounding the legality of their use under the Fourth Amendment. Courts should deny law enforcement requests for geofence warrants, given that individuals have a reasonable expectation of privacy to their location information. These warrants also fail to meet the two requirements mandated by the Fourth Amendment for the issuance of a warrant: probable cause and particularity.

Geofence warrants impede significantly on individuals’ privacy rights. This is mainly because geofence warrants enable law enforcement to easily and efficiently track people’s locations while also obtaining their highly personal information, including email addresses, phone numbers, and details about services used by the device owner.⁶ Access to this information opens “an intimate window into a person’s life, revealing not only [their] particular movements, but through them [their] ‘familial, political, professional, religious, and sexual associations.’”⁷ Unrestrained access to this information not only severely impedes on an individuals’ privacy rights, but can also effectively chill speech and civil rights.⁸ For example, the use of geofence warrants by government agencies has become increasingly popular during protests, and innocent protestors have been dragged into questioning, surveilled, and charged.⁹ These warrants raise privacy concerns and threaten the right to assembly and speech.

The Supreme Court has stated that what a person “seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.”¹⁰ In Carpenter, the Supreme Court established that individuals have a “reasonable expectation of privacy in the whole of their physical movements.”¹¹ This reasonable expectation of privacy remains legitimate even if an individual willingly shares their location with a third party.¹² Therefore, the third-party doctrine, through which individuals may otherwise have no reasonable expectation of privacy regarding information they knowingly and willingly share with third parties, should not extend to cell phone location information.¹³

Because Google users do not truly relinquish their privacy rights to their highly revealing location information, the third-party doctrine should not apply. In carving out an exception to the third-party doctrine in Carpenter, the Court looked to: 1) the loss of voluntary choice in sharing such information with third parties; 2) the ubiquity and inescapability of cell phone usage required for “participation in the modern era”; and 3) the fact that cell-site information belonged to a “qualitatively different category” of information.¹⁴ Likewise, Google users lack a meaningful choice when it comes to sharing their location information, especially since usage of Google’s numerous applications is effectively unavoidable in today’s society. Google dominates the technological market, holding a 91.47% market share of search engines as of January 2024.¹⁵ There are roughly 2.8 billion individuals running Google’s Android software,¹⁶ and there are millions of iPhone owners¹⁷ that use Google applications such as Google search, maps, or weather. The court in In re Search of Information Stored at Premises Controlled by Google reasoned that the use of Google applications—such as Gmail, Google search, Google maps, and YouTube—have become so ubiquitous in use that providing such information to a third-party is not done in a “truly voluntary” manner.¹⁸ Given the pervasiveness of Google applications, individuals “simply cannot forfeit the protections of the Fourth Amendment for years of precise location information by selecting ‘YES, I’M IN,’” when agreeing to the terms and conditions of these applications.¹⁹

The use of geofence warrants raises other Fourth Amendment concerns as well. The Fourth Amendment protects us from “unreasonable searches and seizures,” as the stipulation of a warrant is only granted when the government can demonstrate both probable cause and particularity.²⁰ The Court has stated that the probable cause standard under the Fourth Amendment “is a practical, nontechnical conception”²¹ that “deals with probabilities and depends on the totality of the circumstances.”²² Probable cause is found when “‘the facts and circumstances within their (the officers’) knowledge and of which they had reasonably trustworthy information [are] sufficient in themselves to warrant a man of reasonable caution in the belief that’ an offense has been or is being committed.”²³ The government must also show that there is probable cause “that evidence of the crime will be located at the place to be searched.”²⁴ Therefore, the government must demonstrate a “nexus . . . between the item to be seized and criminal behavior.”²⁵ The Fourth Amendment prohibits the use of general or open-ended warrants.²⁶ The Supreme Court has continually emphasized that a prohibition on general warrants is underpinned by the Fourth Amendment.²⁷ Circuit courts have additionally found that general warrants are only permissible when there is probable cause that all persons within a specified location are connected to the criminal activity in question, or when a specific location is “dedicated exclusively to criminal activity.”²⁸

In the case of geofence warrants, law enforcement can be granted access to seize and search the information of all individuals that fall within its parameters, regardless of their innocence or whether they have any connection to the crime. Therefore, innocent individuals’ right to privacy may be stripped simply due to their proximity to a crime. It is for this reason that certain courts have been rightfully reluctant to grant such warrants even when authorities have probable cause that information concerning the crime and the unidentified suspect exists within its location.²⁹ These courts found such warrants unconstitutional, because the officers failed to show probable cause that each person located within the geofence’s location was in any way “involve[d] in the offense or with the Unknown Subject.”³⁰

The Fourth Amendment additionally requires that warrants particularly describe “the place to be searched, and the persons or things to be seized.”³¹ The Supreme Court made clear in Marron v. United States that the purpose of the requirement is to “make[] general searches . . . impossible and preven[t] the seizure of one thing under a warrant describing another.”³² Therefore the two prongs of the Fourth Amendment, probable cause and particularity, function to “ensure[] that [a] search will be carefully tailored to its justifications, and will not take on the character of the wide-ranging exploratory searches the Framers intended to prohibit.”³³ In order to meet the degree of specificity required by the particularity prong, search warrants must satisfy breadth limitations. Breadth requires that “the scope of the warrant be limited by the probable cause on which the warrant is based.”³⁴ A warrant whose “time, location, and overall scope of the search are consistent with the probable cause [set forth]” fulfills the constitutional boundaries laid out under breadth.³⁵ The Fourth Amendment’s “particularity requirement guards against” the “unguided discretion of the officers executing the warrant,” but it does not “eliminate all [of their] discretion.”³⁶ Therefore, warrants must be “sufficiently specific to permit the rational exercise of [minimal] judgment [by the executing officers] in selecting what items to seize.”³⁷ In determining the constitutionality of a search, courts must look to the reasonableness of the search, which is the “touchstone of the Fourth Amendment” and is ascertained “by assessing, on the one hand, the degree to which it intrudes upon an individual’s privacy and, on the other, the degree to which it is needed for the promotion of legitimate governmental interests.”³⁸

Although law enforcement has a legitimate interest in tracking down suspects of criminal offenses, there is a limitation on the means and the extent to which the Government can do so. In making this determination, courts must look to the level of intrusion and determine whether the Government’s pursuit goes beyond the reasonable expectations of protection afforded by the Constitution. Many geofence warrants fail to establish an “objective procedure” for the police to seize identifying information of the devices found within the locations, meaning “the police [] are not limited in their discretion in selecting cell phones they deem relevant.”³⁹ Given the ease with which the government can deanonymize user information, often without the need for an additional warrant, police officers have considerable discretion to search and obtain identifying information of innocent individuals.⁴⁰ Providing law enforcement unbridled power to search and seize sensitive location information on numerous persons, solely because of their propinquity to a crime, violates the tenets of the Fourth Amendment.⁴¹ Permitting such a warrant would expose all persons, regardless of their connection to a crime (or lack thereof), to the prying and exploratory eyes of the government without the protections historically ensured by the Fourth Amendment. We cannot accept that advancements in technology may eradicate our guaranteed constitutional protections.

Despite the clear constitutional issues raised by geofence warrants, circuit courts remain split on their constitutionality, thereby allowing for their continued employment by law enforcement.⁴² We are now living in a digital era, where our information—from our conversations with Alexa to our location data—is constantly stored, sold, and collected without our knowledge or consent. The importance of ensuring that laws regulate and protect our privacy and constitutional rights is more pivotal than ever before.

* Shirin Asgari is a 3L at New York University School of Law. This piece is a commentary on the 2023 problem at the Cybersecurity Moot Court Competition, hosted by University of California, Los Angeles. The problem involved the constitutionality of geofence warrants under the Fourth Amendment. The views expressed in this piece do not necessarily reflect the views of the author. Rather, this article is a distillation of one side of the argument made by the team at the Cybersecurity Moot Court Competition.

1. 138 S. Ct. 2206 (2018).

2. 444 U.S. 85, 91 (1979).

3. Geofence Warrants, ACLU 3 (Apr. 28, 2022), https://www.aclu-wi.org/sites/default/files/wysiwyg/geofencing_4-28-22_edit_1.pdf; see also Elaine Silvestrini, Your Smartphone May Get You Caught Up in a ‘Geofence Warrant’, The Legal Examiner (Nov. 17, 2020), https://www.legalexaminer.com/legal/your-smartphone-may-get-you-caught-up-in-a-geofence-warrant/ (discussing the logistics of geofence warrants).

4. Dale Chappell, Geofencing Warrants Are Putting Civil Rights and Free Speech in Jeopardy, Crim. Legal News (Apr. 2022), https://www.criminallegalnews.org/news/2022/mar/15/geofencing-warrants-are-putting-civil-rights-and-free-speech-jeopardy/.

5. Note, Geofence Warrants and the Fourth Amendment, 134 Harv. L. Rev. 2508, 2508 (2021) (discussing the distressing criminal implications created by geofence warrants by examining Zachary McCoy’s case ).

6. See, e.g., Chappell, supra note 4.

7. Carpenter, 138 S. Ct. at 2217–18 (quoting United States v. Jones, 565 U.S. 400, 415 (2012) (Sotomayor, J., concurring)).

8. See Sanchez v. L.A. Dep’t of Transp., 39 F.4th 548, 555 (9th Cir. 2022) (holding that under the Fourth Amendment, “when an individual ‘seeks to preserve something as private,’ and that expectation of privacy is ‘one that society is prepared to recognize as reasonable,’ government intrusion into that private sphere generally requires a search warrant supported by probable cause”) (quoting Smith v. Maryland, 442 U.S. 735, 10 (1979)); see also United States v. Jones, 565 U.S. 400, 408 (2012) (holding that warrantless use of GPS tracking on suspect’s car constituted a search and was therefore in violation of the Fourth Amendment).

9. The Bureau of Alcohol, Tobacco, Firearms and Explosives used geofence warrants to obtain information on innocent, law-abiding protestors who attended a Black Lives Matter protect in Kenosha, Wisconsin. Chappell, supra note 4; Alfred Ng, Geofence Warrants: How Police Can Use Protesters’ Phones Against Them, CNET (June 16, 2020, 9:52 AM), https://www.cnet.com/news/privacy/geofence-warrants-how-police-can-use-protesters-phones-against-them/; Kim Lyons, Police in Minneapolis Reportedly Used a Geofence Warrant at Floyd Protest Last Year, The Verge (Feb. 7, 2021, 11:18 AM), https://www.theverge.com/2021/2/7/22271068/police-minneapolis-geofence-warrant-george-floyd-protests-google.

10. Katz v. United States, 389 U.S. 347, 351 (1967).

11. 138 S. Ct. at 2210 (declining to provide the government with unlimited access to an individual’s physical location through data collected by their wireless carrier).

12. Id. at 2220.

13. Id.; see also Smith, 442 U.S. at 743–44 (finding that the extraction of dial information through the use of a pen register did not constitute a search since it was provided voluntarily and knowingly by callers to phone companies for commercial use); see also United States v. Miller, 425 U.S. 435, 435 (1976) (holding that an individual lacked a reasonable expectation of privacy over bank statements they voluntarily provided to their bank).

14. Carpenter, 138 S. Ct. at 2210, 2216 (noting also that “there is a world of difference between the limited types of personal information addressed in Smith and Miller and the exhaustive chronicle of location information casually collected by wireless carriers today”).

15. Search Engine Market Share Worldwide, Statcounter GlobalStats, https://gs.statcounter.com/search-engine-market-share (last visited Mar. 1, 2024).

16. David Curry, Android Statistics, Business of Apps (Mar. 1, 2024), https://www.businessofapps.com/data/android-statistics/.

17. Ryan Nakashima, AP Exclusive: Google Tracks Your Movements, like it or Not, AP News (Aug. 13, 2018, 6:15 PM), https://apnews.com/article/828aefab64d4411bac257a07c1af0ecb.

18. 481 F. Supp. 3d 730, 737 n.4 (N.D. Ill. 2020) (hereinafter “Google I”) (denying a government’s geofence warrant for its lack of probable cause and particularity).

19. United States v. Chatrie, 590 F. Supp. 3d 901, 936 (E.D. Va. 2022).

20. U.S. Const. amend. IV (“The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”).

21. Illinois v. Gates, 462 U.S. 213, 231 (1983).

22. Maryland v. Pringle, 540 U.S. 366, 371 (2003).

23. Brinegar v. United States, 338 U.S. 160, 175–76 (1948) (quoting Carroll v. United States, 267 U.S. 132, 162 (1925)).

24. Gates, 462 U.S. at 238.

25. Warden, Md. Penitentiary v. Hayden, 387 U.S. 294, 307 (1967).

26. Ybarra, 444 U.S. at 91 (ruling that “a person’s mere propinquity to others independently suspected of criminal activity does not, without more, give rise to probable cause to search that person”).

27. See, e.g., Carpenter, 138 S. Ct. at 2213; see also United States v. Riley, 906 F.2d 841, 845 (2d Cir. 1990); Stanford v. Texas, 379 U.S. 476, 480 (1965); Marcus v. Search Warrant of Prop., 367 U.S. 717, 738 (1961) (Black, J., concurring).

28. Marks v. Clarke, 102 F.3d 1012, 1029 (9th Cir. 1996); see also, Owens v. Lott, 372 F.3d 267, 276 (4th Cir. 2004) (“[A]n ‘all persons’ warrant can pass constitutional muster if the affidavit and information provided to the magistrate supply enough detailed information to establish probable cause to believe that all persons on the premises at the time of the search are involved in criminal activity.”).

29. See Google I, 481 F. Supp. 3d at 745 (“[E]ven small-scale expansions of the geofences increased the likelihood of capturing the identities and locations of uninvolved persons, providing another reason why the warrant was overbroad.”); see also In re Search of Info. Stored at the Premises Controlled by Google, No. KM-2022-79, 2022 Va. Cir. LEXIS, at *21 (Va. Cir. Feb. 24, 2022) (hereinafter “Google III”) (denying a geofence search warrant for failure to establish particular probable cause, despite “surveillance video confirm[ing] [the suspects] were in front of the motel using their cell phones just before the shooting”).

30. Google I, 481 F. Supp. 3d at 751.

31. U.S. Const. amend. IV.

32. 275 U.S. 192, 196 (1927).

33. Maryland v. Garrison, 480 U.S. 79, 84 (1987).

34. United States v. Manafort, 313 F. Supp. 3d 213, 231 (D.D.C. 2018) (quoting United States v. Hill, 459 F.3d 966, 973 (9th Cir. 2006)).

35. Google III, 2022 Va. Cir. LEXIS, at *14.

36. Riley, 573 U.S. at 844–45.

37. United States v. LaChance, 788 F.2d 856, 874 (2d Cir. 1986) (quoting United States v. Vargas, 621 F.2d 54, 56 (2d Cir. 1980)).

38. United States v. Knights, 534 U.S. 112, 118–19 (2001) (quoting Wyoming v. Houghton, 526 U.S. 295, 300 (1999)).

39. Google III, 2022 Va. Cir. LEXIS, at *23.

40. Google I, 481 F. Supp. 3d at 749 (stating that the “[c]ourt sees no practical difference between a warrant that harnesses the technology of the geofence, easily and cheaply, to generate a list of device IDs that the government may easily use to learn the subscriber identities, and a warrant granting the government unbridled discretion to compel Google to disclose some or all of those identities”).

41. Whitehead v. Commonwealth, 278 Va. 300, 313 (2009) (holding that even though law enforcement officers had probable cause to search a vehicle because a trained police dog detected narcotics, they lacked “probable cause sufficiently particularized” to search the individuals within the car for narcotics).

42. Compare Google I, 481 F. Supp. 3d, and Google III, 2022 Va. Cir. LEXIS (Cir. Ct. Feb. 24, 2022) (both ruling that the geofence warrant was unconstitutional since it lacked probable cause and particularity), with Matter of Search Warrant Application for Geofence Location Data Stored at Google Concerning an Arson Investigation, 497 F. Supp. 3d 345, 349 (N.D. Ill 2020) (holding that the “government’s application for location data within six geofence areas relating to an arson investigation satisfies the probable cause and particularity requirements of the Fourth Amendment”).