The Wrong Analogy: Carpenter, Chatrie, and the ALPR Question

Introduction

When Flock Safety was founded in 2017, its business model primarily centered around providing automated license plate readers (ALPRs) to private neighborhoods and homeowners. But in 2019, the company began soliciting individual police departments to adopt multi-camera ALPR leases and trials to track stolen vehicles and suspects [1]. Since then, more than 120,000 Flock cameras have been installed in 49 U.S. states [2]. In the past two years, however, public outcry, protests, and acts of vandalism have caused local governments to begin reversing contractual decisions as early as 2024. In August 2026 alone, more than 90 individual cities, counties, sheriffs, and other institutions terminated, suspended, or declined to renew their surveillance technology agreements or contracts with Flock Safety [3].

As salient as the public policy is, the relevant questions here are legal ones — and a pending appeal may provide the first answer. In 2024, Lee Schmidt and Crystal Arrington, residents of Norfolk, Virginia, sued the city over its use of Flock cameras to record Schmidt’s and Arrington’s vehicles 475 and 325 times, respectively, over the course of about four and a half months [4]. The plaintiffs claim that both the collection of data tracking their daily movements throughout the city and the preservation of those records for 21 days amount to an unconstitutional search under the Fourth Amendment of the U.S. Constitution. U.S. District Judge Mark Davis granted summary judgment to Norfolk in Schmidt v. City of Norfolk, ruling that the plaintiffs were unable to sufficiently demonstrate that the system was capable of tracking “the whole of [one's] physical movements” [5] — the phrase on which the appeal is likely to turn when the Fourth Circuit hears argument in December 2026 [6]. Schmidt — in asking whether a government’s operation of an ALPR network that records and stores residents’ driving history amounts to a Fourth Amendment search — will be the first federal appeal to rule on the issue.

The outcome of the case may initially appear to hinge on two recent cases linking Fourth Amendment rights to law enforcement tracking devices: Carpenter v. United States (2018) and Chatrie v. United States (2026) [7]. Both cases give the impression that extending Fourth Amendment protections to Schmidt v. City of Norfolk will prove demanding yet plausible. However, impressions are rarely indicative of rulings. In fact, compared with Schmidt, neither case supplies a plainly analogous argument for ALPR plaintiffs. While Carpenter and Chatrie both protect private records held by a third party, Schmidt concerns first-party government records. Schmidt more accurately asks whether aggregating individually lawful public observations can become a search — a question better answered by United States v. Knotts (1983) and the Fourth Circuit’s own decision in Leaders of a Beautiful Struggle v. Baltimore Police Department (2021) — cases that rule on government surveillance as it pertains to Fourth Amendment searches [8].

This Article proceeds in three parts. Part I reviews the logic behind the rulings in Carpenter and Chatrie. Part II argues they are the wrong analogy — both concern compelled disclosure of records from a mobile device. Part III contends that Knotts and Leaders of a Beautiful Struggle better frame the question plaintiffs must answer — whether aggregating public observations can become a search [9].

I. What Carpenter and Chatrie Held

In Carpenter, the FBI obtained 127 days of historical cell-site location information (CSLI) from Timothy Carpenter’s wireless carriers [10]. It did so under the Stored Communications Act, which requires only “reasonable grounds” (if data is relevant and material to an ongoing criminal investigation) to seek CSLI [11]. Writing for a 5-4 majority, Chief Justice Roberts reasoned that cell-site records differ in kind from bank records and dialed numbers, and therefore the government's acquisition of his historical cell-site information without a warrant violated his Fourth Amendment rights. The Carpenter Court emphasized four factors in its ruling: one, that CSLI provides all-encompassing records of a person’s physical location; two, that the government has the ability to retrospectively track individuals over extended periods; three, that the data reveals intimate details of a person’s life; and four, that logging location data is automatic with no affirmative act by the user [12]. These factors, in conjunction, sufficiently demonstrated, the majority held, that cell-site data is qualitatively different from other unprotected records [13].

Chatrie, the more recent case, arose from a 2019 bank robbery in Virginia. Police obtained a geofence warrant that required Google to identify every device with Location History enabled near the bank at the time of the crime. Using a three-step process to narrow the suspect pool, police eventually identified Okello Chatrie as the primary person of interest [14]. In June 2026, the Court held 6-3 that acquiring location history constitutes a Fourth Amendment search, but remanded the case without deciding whether Virginia’s actions were unconstitutional. Justice Kagan, writing for the majority, articulated that individuals retain a reasonable expectation of privacy in their location records even when a third party like Google holds them [15]. The Court stressed two dangers in the search process that infringe on one's reasonable expectation of privacy: one, that even brief location data can reveal sensitive information, and two, that location history can show when a person is inside a home [16].

To begin to understand what relevance Chatrie and Carpenter could have to Schmidt, it is important to first consider what each case actually held. Both cases involve the government compelling a company to turn over data records generated by a phone the suspect carried. Both rulings also protect “the whole of [one's] physical movements” [17]. With the inclusion of that phrase, the Court has established that a threshold exists, but where exactly that threshold is has yet to be ruled on. ALPRs, it seems, would certainly expand the meaning of “the whole of [one's] physical movements,” because unlike CSLI, an ALPR network captures only fragments of a person’s movements. So the question remains: how many fragments make up the whole?

Taken together, Carpenter and Chatrie offer ALPR plaintiffs two openings. Carpenter held that aggregated location data becomes a search once it captures “the whole of [one's] physical movements” without defining a threshold for that phrase [18]. And Chatrie suggested that even brief location data can be revealing, so a short retention period does not defeat a Fourth Amendment challenge [19]. But both openings are built for a particular kind of data: records generated by a cell phone that are, first, held by a company and, second, disclosed to a government under compulsion. As Part II argues, that makes Carpenter and Chatrie the wrong analogy for Schmidt.

II. The Wrong Analogy

Carpenter and Chatrie appear to offer ready-made precedent for ALPR plaintiffs, but the legal rationale underlying both decisions depends on features that do not necessarily apply to ALPR networks.

First, both are third-party doctrine cases: in each, the government compelled a third-party company to disclose records it had compiled [20]. The question, then, was whether sharing data with a company forfeits Fourth Amendment protection — a question that is not relevant to Schmidt, in which Norfolk officers can query the system independently [21]. Second, both cases concern a device that remains with its owner at all times, including indoors and inside the owner’s own home. In fact, Chatrie’s own ruling stressed that location history can reveal when a person is inside of a home — information whose collection clearly constitutes a Fourth Amendment search [22]. A fixed camera, as in the case of ALPRs, records a single point on a public road. Third, the data being collected remains fundamentally different in type. Chatrie protected location history partly because users treat it as their own and their consent to share it is ambiguous [23]. A license plate, on the other hand, is issued by the state, which requires drivers to display it precisely so the vehicle can be identified in public [24].

Measured against Carpenter’s four factors, ALPR data presents a mixed picture. While the 21-day database allows officers to reconstruct routes [25], Norfolk’s ALPR system does not satisfy the other three factors in Carpenter [26]: One, the records kept by ALPRs are not all-encompassing; two, the data is not intimate and does not track an individual in a home; and three, the data logging includes an affirmative act when citizens decide to drive a car on a public road. To prevail, then, plaintiffs must establish something neither case decided — specifically, that aggregating individually lawful public observations can become a search under the Fourth Amendment. That question is more readily answered by Knotts and Leaders of a Beautiful Struggle.

III. The Right Analogy

If Schmidt does indeed turn on whether aggregating public observations can become a search, two precedents seem to better frame the answer.

The city of Norfolk's strongest precedent is United States v. Knotts (1983). Using a radio beeper — which was placed, with the seller's permission, inside a container of chemical ingredients used to manufacture illegal drugs — police tracked a suspect’s car on public highways [27]. The Court held 9-0 that this did not constitute a search, because a driver has no reasonable expectation of privacy in movements anyone could observe [28]. It would follow that ALPRs fit within this framework. However, Knotts also reserved the question of “dragnet-type law enforcement practices” [29] — those that involve coordinated policing or surveillance methods that gather information or detain people en masse. A citywide network that logs every passing car could plausibly be argued to be such.

The plaintiffs’ strongest case belongs to the Fourth Circuit. In Leaders of a Beautiful Struggle v. Baltimore Police Department (2021), the en banc court held that accessing data from Baltimore’s warrantless aerial surveillance program was a search [30]. Like an ALPR system, the Aerial Investigation Research (AIR) program captured only public activity: planes photographed much of the city by day, and the photographs were then retained for weeks [31]. The Fourth Circuit nonetheless held 8-7 that, by letting police deduce a person’s movements over time, the program crossed the line Carpenter drew — that individuals retain a reasonable expectation of privacy in "the whole of [one's] physical movements" [32]. Leaders thus establishes that a government-run system collecting only public observations can still conduct a search if that data is aggregated and kept for periods of time.

In granting summary judgment, Judge Davis relied most heavily on Carpenter and Leaders, concluding that Norfolk’s 176 Flock cameras — broken down into 75 camera clusters and spread across 66 square miles, with photographs retained for 21 days — are not nearly as omnipresent as the phone tracking in Carpenter or the aerial surveillance in Leaders and therefore do not merit the same protection [33]. What the ruling left out, though, matters more than what it concluded: a principled test for where the line falls. A year earlier, in denying Norfolk’s motion to dismiss, Judge Davis had written that “a reasonable person could believe that society’s expectations, as laid out by the Court in Carpenter, are being violated by the Norfolk Flock system” [34]. Without a rule that determines which facts matter, future Fourth Amendment challenges to ALPRs will turn on case-by-case judgment calls. By deliberately leaving this door open, Judge Davis made it necessary for a higher court to establish a standard for ALPRs and Fourth Amendment rights. Importantly, Judge Davis’s ruling and Leaders mark two points on either side of the line. Norfolk’s fixed cameras fell short, while Baltimore’s citywide aerial coverage crossed it [35]. Schmidt asks the Fourth Circuit to say where between them the line falls, and the answer, if consistent with this framework, will have to set tangible limits on how densely cameras can be placed and how long data can be kept.

It is clear that Carpenter and Chatrie will dominate the briefing in Schmidt, but they cannot decide it. Both cases protect records that a third-party company was compelled to disclose about a mobile device [36]. Norfolk’s cameras are fixed in place on a public road and are, importantly, government-operated and government-owned. Whatever force those decisions have, it reaches ALPR only through the ambiguous "whole of [one's] physical movements" ruling cited in Leaders [37].

The question in Schmidt therefore is one neither Supreme Court case answered. Schmidt asks whether many individually lawful public observations can, together, become a search. Knotts suggests they cannot; Leaders suggests that, at some scale, they can. The Fourth Circuit now has the chance to say where the line is drawn. If it declines to draw that line, the question will very likely be appealed to the U.S. Supreme Court. For now, the issue will pass through city councils and state legislatures, which are deciding, contract by contract, how much of their residents’ movements the government should be able to see.

References

[1] Jacob Sullum, “The Belated Backlash Against Flock Cameras,” Reason, August 31, 2026, https://reason.com/2026/08/31/the-belated-backlash-against-flock-cameras/.

[2] Flock Safety, “The Price of ‘Free’ LPR,” June 25, 2026, https://www.flocksafety.com/blog/the-price-of-free-lpr.

[3] Sophie Hurwitz, “Flock Is Canceled—And Its Competitors Are Profiting,” Mother Jones, September 3, 2026 (reporting a tally by Secure Justice), https://www.motherjones.com/politics/2026/09/flock-contracts-cancelled-cameras-alpr-rekor-axon-florida-texas/.

[4] Schmidt v. City of Norfolk, 819 F. Supp. 3d 492 (E.D. Va. 2026).

[5] Ibid.

[6] Schmidt v. City of Norfolk, No. 26-1227 (4th Cir.) (argument tentatively set for December 8–11, 2026); Jeffrey B. Welty, “Quick Thoughts about Flock Cameras, the Fourth Amendment, and the Courts,” North Carolina Criminal Law (blog), UNC School of Government, September 14, 2026, https://nccriminallaw.sog.unc.edu/2026/09/14/quick-thoughts-about-flock-cameras-the-fourth-amendment-and-the-courts/.

[7] Carpenter v. United States, 585 U.S. 296 (2018); Chatrie v. United States, 609 U.S. ___ (2026).

[8] United States v. Knotts, 460 U.S. 276 (1983); Leaders of a Beautiful Struggle v. Baltimore Police Department, 2 F.4th 330 (4th Cir. 2021).

[9] 460 U.S. 276 (1983); 2 F.4th 330 (4th Cir. 2021).

[10] 585 U.S. 296 (2018).

[11] Stored Communications Act, 18 U.S.C. § 2703(d).

[12] 585 U.S. 296 (2018).

[13] Ibid.

[14] 609 U.S. ___ (2026).

[15] Ibid.

[16] Ibid.

[17] 585 U.S. 296 (2018); 609 U.S. ___ (2026).

[18] 585 U.S. 296 (2018).

[19] 609 U.S. ___ (2026).

[20] 585 U.S. 296 (2018); 609 U.S. ___ (2026).

[21] 819 F. Supp. 3d 492 (E.D. Va. 2026).

[22] 609 U.S. ___ (2026).

[23] Ibid.

[24] Va. Code Ann. § 46.2-716(A).

[25] 819 F. Supp. 3d 492 (E.D. Va. 2026).

[26] 585 U.S. 296 (2018).

[27] 460 U.S. 276 (1983).

[28] Ibid.

[29] Ibid.

[30] 2 F.4th 330 (4th Cir. 2021).

[31] Ibid.

[32] Ibid.

[33] 819 F. Supp. 3d 492 (E.D. Va. 2026).

[34] Schmidt v. City of Norfolk, No. 2:24-cv-621 (E.D. Va. February 5, 2025) (order denying motion to dismiss).

[35] 819 F. Supp. 3d 492 (E.D. Va. 2026); 2 F.4th 330 (4th Cir. 2021).

[36] 585 U.S. 296 (2018); 609 U.S. ___ (2026).

[37] 2 F.4th 330 (4th Cir. 2021).