I. Introduction

On June 29, 2026, the United States Supreme Court issued its opinion in Chatrie v. United States. By a 5-1-3 vote, the Court held that police officers conducted a Fourth Amendment search when they gathered Okello Chatrie’s historical cell phone location data from Google via a geofence warrant.¹ This extended the Court’s opinion in Carpenter v. United States.²

Although the Court’s holding focused on geofence warrants, the Court’s reasoning raises broader questions about privacy, the Fourth Amendment, and the digital age. Some argue that technological advances that allow the government to track its citizens “may ‘alter the relationship between citizen and government in a way that is inimical to democratic society.'”³ Others view technological advances as valuable tools for crime prevention and investigation efforts, ultimately promoting justice.⁴ This article will discuss the Chatrie Court’s reasoning, consider its analytical framework in the context of other emerging surveillance technologies, and consider prospective outlook for litigants.

II. A Brief Overview of Relevant Fourth Amendment Jurisprudence

The Fourth Amendment protects “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.”⁵ Prior to 1967, the Court analyzed Fourth Amendment claims through a property lens, asking whether the government physically trespassed onto a “constitutionally protected area.”⁶ As digital technology has raised new virtual “places” where the government and citizens’ privacy interests intersect, the Fourth Amendment has shifted to account for those changes. The decisions below illustrate that evolution and provide the doctrinal foundation for Chatrie.

a. Reasonable Expectation of Privacy

In Katz v. United States, the Court fundamentally expanded its Fourth Amendment analysis in noting that “the Fourth Amendment protects people, not places.”⁷ The Katz Court rejected the exclusively property-based analysis, recognizing that the government conducts a search when it impedes upon an individual’s “reasonable expectation of privacy.”⁸ Justice Harlan’s concurrence recognized the two-part inquiry into whether an individual has a reasonable expectation of privacy. First, the individual must have “exhibited an actual (subjective) expectation of privacy.”⁹ Second, that expectation must “be one that society is prepared to recognize as ‘reasonable.'”¹⁰ Katz importantly shifted the focus from trespass to privacy interests, and serves as the foundation for the Court’s “20th century” Fourth Amendment jurisprudence.¹¹

b. The Third-Party Doctrine

Following Katz, the Court confronted the extent to which individuals retain a reasonable expectation of privacy in information they voluntarily disclose to others. In United States v. Miller, the Court held that a bank depositor did not have a reasonable expectation of privacy in bank records “because the records were ‘voluntarily conveyed to the bank[] and exposed to [its] employees in the ordinary course of business.'”¹² Because the “depositor [took] the risk, in revealing his affairs to another, that the information [would] be conveyed by that person to the Government,” there is no legitimate expectation of privacy in those records.¹³

Then, the Court applied this idea in Smith v. Maryland, holding that the defendant had no legitimate expectation of privacy in the phone numbers he dialed from his landline.¹⁴ Because the defendant “voluntarily conveyed numerical information to the telephone company and ‘exposed’ that information to its equipment in the ordinary course of business,” he “assumed the risk that the company would reveal to police the numbers he dialed.”¹⁵

What came to be known as the third-party doctrine has remained an important limit on the Katz reasonable-expectation-of-privacy analysis, as information that is voluntarily disclosed to a third party does not receive Fourth Amendment protection. However, the doctrine’s application has become increasingly difficult in the digital age. Participation in society in the digital age often requires sharing large amounts of information with third-party service providers. The Court in Carpenter and Chatrie specifically noted that Miller and Smith remain good law.¹⁶ However, while concurring with the majority in Chatrie, Justice Gorsuch suggested that the Court had given the third-party doctrine a “quiet burial.”¹⁷

c. Digital Privacy

As digital technology has become indivisibly integrated into daily life, the Court has recognized that Fourth Amendment principles do not always align neatly with modern forms of surveillance.

In United States v. Jones, the court held that the government conducted a Fourth Amendment search when it attached a GPS device to a vehicle and monitored the defendants’ movements.¹⁸ The majority relied on a property-based analysis, confirming that the “Katz reasonable-expectation-of-privacy test has been added to, not substituted for, the common-law trespassory test.”¹⁹ So, when law enforcement trespassed in installing a GPS on the defendant’s car and then used the GPS data, that was a search.²⁰ However, five justices concluded that the prolonged GPS monitoring implicated reasonable expectations of privacy as well.²¹ Concurring, Justice Sotomayor explained that the government conducted a search under both a property-based analysis and a reasonable-expectation-of-property analysis.²² Concurring in the judgment, Justice Alito, joined by three justices, argued that the government action was invasive, not because of the GPS attaching, but because of the prolonged surveillance.²³

The concurring opinions in Jones raised concerns that would become central to the Court’s later digital privacy opinions. Justice Sotomayor observed that prolonged location monitoring can reveal “a wealth of detail,” including trips that one would consider to be “indisputably private,” such as trips “to the psychiatrist, the plastic surgeon, the abortion clinic, the AIDS treatment center, the strip club, the criminal defense attorney, the by-the-hour motel, the union meeting, the mosque, synagogue or church, the gay bar and on and on.”²⁴ Both Carpenter and Chatrie echoed this observation.²⁵ Scholars have described this concept as the mosaic theory of the Fourth Amendment, which considers whether “the type and amount of information gathered, when viewed in the aggregate, is so revealing that the action should be considered a Fourth Amendment search, even if the individual data points do not reveal that much in isolation.”²⁶ Although the Jones majority did not adopt the mosaic theory, these concerns expressed in the concurrences foreshadowed the Court’s analysis in Carpenter and Chatrie.

The Court was faced with a new and pervasive technology in Riley v. California: cell phones.²⁷ There, the Court held that “a warrant is generally required before” searching a cell phone, including “when seized incident to arrest.”²⁸ The Court noted that cell phones are uniquely ubiquitous: “modern cell phones . . . are now such a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy.”²⁹

These principles culminated in Carpenter v. United States, where the Court declined to extend the third-party doctrine to seven days of historical cell-site location information (“CSLI”).³⁰ Although wireless carriers maintain CSLI records, the Court held that “individuals have a reasonable expectation of privacy in the whole of their physical movements.”³¹ In declining to apply the third-party doctrine, the Court observed that “[c]ell phone location information is not truly ‘shared’ as the term is normally understood.”³² Rather, “cell phones and the services they provide are ‘such a pervasive and insistent part of daily life’ that carrying one is indispensable to participation in modern society.”³³ Accordingly, the Court rejected the idea that cell phone users voluntarily disclose their location information in the traditional sense, as “a cell phone logs a cell-site record by dint of its operation, without any affirmative act on the user’s part beyond powering up.”¹⁵

The Court further emphasized the revealing nature of CSLI, echoing Justice Sotomayor in Jones: because people carry their cell phones everywhere, a “cell phone faithfully follows its owner beyond public thoroughfares and into private residences, doctor’s offices, political headquarters, and other potentially revealing locales.”³⁴ Thus, collecting CSLI is particularly invasive as it “achieves near perfect surveillance, as if it had attached an ankle monitor to the phone’s user.”³⁵ In reaching this conclusion, Carpenter focused on CSLI’s “depth, breadth, and comprehensive reach” and the “inescapable and automatic nature of its collection.”³⁶ At least one scholar observed that the Court “potentially adopted” the mosaic theory with this ruling.³⁷

In the wake of the Court’s decision, University of Utah College of Law’s Professor Tokson synthesized the “Carpenter test” into three factors: “(1) the revealing nature of the data collected; (2) the amount of data collected; and (3) whether the suspect voluntarily disclosed their information to others.”³⁸ While a significant win for privacy proponents, Carpenter left open important questions, including the implications for real-time collection, geofencing and tower dumps, and length of time at which surveillance becomes a search.³⁹

III. Geofence Warrants and the Decision in Chatrie

a. What is a Geofence Warrant?

The Court’s decision in Chatrie comes amid the increasing use of warrants that commentators have referred to as reverse search warrants. Reverse warrants operate backwards: “[r]ather than directing searches at a suspect based on evidence,” “reverse warrants collect information on many people in order to find a suspect.”⁴⁰

A geofence warrant is a type of reverse warrant that allows law enforcement to obtain information about devices that were within a virtual perimeter during a specified period of time.⁴¹ Because many Google users have enabled a service called “Location History,” which “records the locations of a user’s cell phone every two minutes or so,” Google can provide this information to law enforcement.¹⁵ Although Google was the data provider in this case, other platforms such as Apple, Lyft, Snapchat, and Uber have also received geofence warrant demands.⁴²

Because geofence warrants search backwards for a suspect, they “often run a high risk of sweeping in innocent users.”⁴³ And because law enforcement typically request a geofence that covers more area than the location of the crime, “[i]t is common for a geofence to cover private homes, apartment buildings, government buildings, hotels, places of worship, busy roads, and other locations that law enforcement has not identified particularized probable cause to search.”¹⁵

In 2016, Google received its first geofence warrant demand.⁴⁴ In 2018, Google received around 1000 warrants.¹⁵ In 2020, it received over 11,000.¹⁵ Between 2021 and 2023, geofence warrants were “over a quarter of all law enforcement demands the company received from U.S. law enforcement.”¹⁵

Geofence warrants typically proceed in a three-step process. First, the data provider (here, Google) provides anonymized location data for cell phones within the geofence.⁴⁵ Second, law enforcement reviews the initial data and requests further, still anonymized, information on a subset of users.¹⁵ Third, law enforcement reviews the data, narrows the pool again, and requests identifying information for the remaining devices.¹⁵

b. Chatrie: Background

Following a bank robbery in Virginia, law enforcement engaged in this three-step geofence warrant process.⁴⁶ Okello Chatrie was one of the users on the final list.⁴⁷ After being charged with robbery, Chatrie moved to suppress his location information, arguing that this procedure was a search that violated the Fourth Amendment.¹⁵ The district court agreed, but declined to apply the exclusionary rule, finding that the good-faith exception applied.⁴⁸ A Fourth Circuit panel affirmed, but alternatively held that there was no search because Chatrie did not have a reasonable expectation of privacy in his Location History, so the government did not need a warrant.⁴⁹ Rehearing en banc, the Fourth Circuit affirmed per curiam in a one-sentence opinion, but was evenly divided on whether a search had occurred.⁵⁰

c. Chatrie: The Court’s Analysis

The Court heavily relied on Carpenter, noting that “everything Carpenter relied on . . . applies as well or better to the police’s accessing of Google’s Location History data.”⁵¹

The Court observed that Location History is more precise than CSLI and thus more invasive. Carpenter‘s CSLI placed the defendant “within a ‘sector ranging from one-eighth to four square miles,” but “Location History pinpointed Chatrie’s location within around twenty meters.”⁵² Further, CSLI reported Carpenter’s location an average of 101 times per day, but Location History reports location an average of 720 times per day.⁵³ Plus, like CSLI, Location History allows for retrospective monitoring, enabling the government to reconstruct information that previously could not be determined and raising “formerly unimaginable ‘privacy concerns.'”⁵⁴ Also, Google users can retrieve their own Location History data on their devices, “resembl[ing] other private materials—think of emails, documents, photographs, or calendars—that even if stored on Google’s servers, a user reasonably views as his own.”⁵⁵ As such, a reasonable person expects those private materials “to be shielded from the ‘inquisitive eyes’ of the government.'”⁵⁶

The Court dismissed the Government’s argument that limited duration brings the investigation outside the scope of the Fourth Amendment, noting that even a brief surveillance can expose intimate information to the government.⁵⁷ Justice Kagan wrote, “we have never understood Fourth Amendment protections as kicking in only once an intrusion ‘goes too far.'”⁵⁸ In answering the duration question held open by Carpenter, the Court concluded that “even two hours of [Location History]” “allows officers to target one-off events of potential interest: a gun rally, say, or a political rally.”¹⁵ Recognizing the novel issue of reverse warrants, Justice Kagan wrote that the “sweep of the official invasion is not made less because the government, with the benefit of hindsight, can pinpoint exactly which few hours of movements it wants to review.”⁵⁹ Ultimately, the Fourth Amendment applies “regardless of ‘the quality or quantity of the information’ the government obtains.⁶⁰ In so doing, the Court appears to endorse the mosaic theory, noting that if “the government can access all of a cell-phone user’s movements in both public and private places,” “it possesses a virtual panopticon⁶¹ with which to scrutinize its citizens’ activities.”⁶² One scholar read Chatrie to mean that “[t]he constitutional threat is not any particular data demand but the existence of centralized, searchable repositories of personal information and the government’s ability to reach into them” and that, as such, “[e]very query is a search because the panopticon exists.”⁶³

As for the third-party doctrine, the Court reaffirmed the two features of CSLI it identified in Carpenter that distinguished it from other disclosures to third parties: (1) the “incomparably revealing nature” of CSLI and (2) the fact that in “no meaningful sense” does a person voluntarily expose the information to a third party. It then found that both these “features … apply equally or better” to Location History.⁶⁴ First, the Court concluded that “Location History is even more ‘revealing’ than CSLI” because it “enables officials to undertake nearly perfect, retrospective surveillance of countless persons and places.”⁶⁵

On the second feature, the Court considered the Government’s argument that, because Google users must affirmatively opt-in to Location History Tracking, it is in fact a voluntary choice made by each user.¹⁵ However, the Court noted that Google repeatedly and frequently prompt users to turn on Location History (and on Android devices, Google informs the user “that his device will not ‘work correctly’ unless he does so”), also “[p]retty much everything a person does on a smartphone requires some kind of opt-in” and thereby shares information with a third party.⁶⁶ Thus, the Court stated that if it were to expand the third-party doctrine to any time a person opts-in, it would defeat the “point of carrying smartphones:” “to use what is on them.”⁶⁷

Some suggest that this is “[t]he end of consent as a constitutional baseline.”⁶⁸ That is, “[i]f participation in the digital ecosystem does not constitute consent to government surveillance, then the consent-and-transfer model that undergirds most existing data governance law is built on a premise the Supreme Court has now rejected.”¹⁵ Professor Solove suggests that, after Chatrie, there are three scenarios in which the third-party doctrine may not apply: (1) “[i]f the data constitutes an ‘exhaustive chronicle’ of one’s life”; (2) “[i]f sharing data or using a device that gathers data is an indispensable part of daily life, then this isn’t to be viewed as sharing data with third parties”; and (3) “if users view their data as their own” even when it is “in the hands of a third party”.⁶⁹

Further, the Court noted that Google users can retrieve their own Location History data on their devices, “resembl[ing] other private materials—think of emails, documents, photographs, or calendars—that even if stored on Google’s serves, a user reasonably views as his own.”⁷⁰ As such, a reasonable person expects those private materials “to be shielded from the ‘inquisitive eyes’ of the government.”⁵⁶ By explicitly mentioning these other types of private materials, one observer noted that “the opinion lays the analytic groundwork for affording constitutional protection to a broad range of cloud-stored personal data.”⁷¹

If we consider Tokson’s Carpenter test, it seems that Chatrie adds factors, including whether or not one reasonably believes the data is his, and whether or not the information system that is drawn from is the kind that would subject many people to surveillance equivalent to a “virtual panopticon.” Chatrie thus appears to endorse the mosaic theory, as the Court focuses on what can be deduced from the information, not simply what was collected. Thus, perhaps as lower courts apply Chatrie, “the more a user treats material entrusted to a provider as his own or the more that material reveals the personal activities of the user, the more likely a court is to find the user maintains a reasonable expectation of privacy in the material.”¹⁵

Concluding, Justice Kagan invoked Justice Brandeis’ dissent in Olmstead v. United States: “Americans had ‘as against the Government, the right to be let alone.'”⁷²

d. The Warrant Question

After concluding that there was a search, the Court remanded the question of “whether the warrant satisfied the Fourth Amendment’s probable cause and particularity requirements at each stage of the search process” to the Fourth Circuit because it was not examined below.⁷³

Justice Jackson filed a concurring opinion, which Justice Sotomayor joined. Justice Jackson agreed that the officers conducted a search, but would have gone further to address the warrant question.⁷⁴ She concluded that “at a minimum the second and third stages of the search process here did not satisfy” the Fourth Amendment’s probable cause and particularity requirements.⁷⁵ At stages two and three of the warrant procedure, “the warrant stated that officers would ‘attempt to narrow down the list’ of devices.”⁷⁶ Because “there was no explicit requirement” that the officers narrow down the list, nor did the warrant include “any criteria that officers would use in their narrowing efforts,” officers did not have to make probable cause determinations at each of these stages in front of a neutral and detached magistrate.⁷⁷ For Justice Jackson, this left too much direction to the officers such that the warrant did not satisfy the Fourth Amendment.⁷⁵

These questions now frame the proceedings on remand. The Fourth Circuit’s treatment of the probable cause and particularity issues may prove to be consequential, determining whether and how law enforcement may use geofence warrants in the future. Moreover, the Fourth Circuit’s resolution of these issues may shape the availability of the good-faith exception in future geofence cases (or reverse warrant cases, more broadly) by clarifying what constitutional limitations officers are expected to understand and follow.⁷⁸

IV. Other Technologies & Emerging Questions After Chatrie

After Chatrie, investigations involving other technologies may be ripe for challenges. “Because rapid technological advances, such as the rise of artificial intelligence, make it impossible to predict how police surveillance will evolve, the Fourth Amendment analysis must remain nimble even as it remains grounded in founding-era traditions.”⁷⁹

This article does not seek to opine on the ultimate constitutionality of law enforcement use of these technologies, nor does it attempt to exhaust every issue or every possible challenge. Rather, it aims to identify and analyze potential challenges to surveillance technologies and data requests that may arise in the wake of Chatrie.

a. Automated License Plate Readers

Automated license plate readers (“ALPRs”) are “high-speed, computer-controlled camera systems that are typically mounted on street poles, streetlights, highway overpasses, mobile trailers, or attached to police squad cars” and have become an increasingly common investigative tool for law enforcement agencies.⁸⁰ ALPR systems use cameras “to automatically capture, analyze, and store vehicle license plate information.”⁸¹ When a license plate comes into view, the camera catches the plate numbers, location, date, and time.⁸² “Some versions can also snap pictures of a vehicle’s occupants and create unique vehicle IDs.”⁸³ This information can be used “to find out where a plate has been in the past, to determine whether a vehicle was at the scene of a crime, to identify travel patterns, . . . to discover vehicles that may be associated with each other,” and “to share their information with thousands of other agencies.”⁸² Many jurisdictions retain plate information, and some retain it indefinitely.⁸⁴ After reviewing records from 200 agencies, the Electronic Frontier Foundation found that ALPRs conducted more than 2.5 billion license plate scans between 2016 and 2017.⁸⁵ In 2019 alone, 82 agencies collected over 1 billion license plate scans.⁸⁶

Like geofence warrants, ALPR systems collect location information regardless of whether a person is suspected of criminal activity.⁸⁷ And ALPRs “leave a data trail.”¹⁵ Additionally, law enforcement can receive real-time alerts when a car moves past a camera.¹⁵ Cars may also fall within the ubiquity concern that cell phones do. As of 2018, 83% of Americans drove a car at least several times per week.⁸⁸ “In jurisdictions with limited or no public transportation, driving may even rival cell phone use as a modern necessity.”⁸⁴

The Supreme Court has not required a warrant for law enforcement to collect license plate information. Generally, the Court has noted that “vehicles capable of traveling on public highways” are “pervasive[ly] regulat[ed],” such that there is no expectation of privacy for license plates.⁸⁹ Additionally, the Court has noted that a “person travelling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another.”⁹⁰ Chatrie reaffirmed that distinction.⁹¹ And in Carpenter, the Court expressly did not call into question “security cameras.”⁹² As for license plates, courts have held that “a motorist has no reasonable expectation of privacy in the information contained on his license plate,” and thus the government’s viewing of one is not a Fourth Amendment search.⁹³

To date, lower courts have largely rejected Fourth Amendment challenges to ALPR systems.⁹⁴ They note that there is no reasonable expectation of privacy when traveling on a public road in plain view, and that the cameras take snapshots, rather than continually tracking a vehicle’s movements.⁹⁵

However, ongoing litigation in the Fourth Circuit illustrates the current doctrinal landscape, as ALPR networks become increasingly ubiquitous. In Schmidt v. City of Norfolk, plaintiffs challenged Norfolk’s network of 176 Flock cameras, alleging that the city’s practice of photographing virtually every passing vehicle violated the Fourth Amendment.⁹⁶ The plaintiffs allege that the network of ALPRs has “become so intrusive that [it] violate[s] individuals’ ‘reasonable expectation of privacy in the whole of their physical movements.'”⁹⁷

Plaintiffs rely on Fourth Circuit precedent in Leaders of a Beautiful Struggle v. Baltimore Police Department.⁹⁸ In Leaders of a Beautiful Struggle, community advocates in Baltimore challenged BPD’s surveillance program, which used cameras that captured “an estimated twelve hours of coverage of around 90% of the city each day,” covering “32 square miles per image per second.”⁹⁹ Any individual image could “be magnified to a point where people and cars are individually visible, but only as blurred dots or blobs.”¹⁵ The images were then used “to track individuals and vehicles from a crime scene and extract information to assist BPD.”¹⁰⁰ Images were stored for forty-five days, but could be stored “indefinitely” if “necessary for legal proceedings.”¹⁵ The Fourth Circuit reasoned that the surveillance program was “like ‘attach[ing] an ankle monitor’ to every person in the city.”¹⁰¹ Relying on Carpenter and Jones, the Court concluded that the “program open[ed] ‘an intimate window’ into a person’s associations and activities,” and thus “violate[d] the reasonable expectation of privacy individuals have in the whole of their movements.”¹⁰²

Plaintiffs also argue that Norfolk’s system allows police to “travel back in time to reconstruct people’s movements.”¹⁰³ But, the district court found that “[p]laintiffs [were] unable to demonstrate that [d]efendants’ ALPR system is capable of tracking the whole of a person’s movements.”¹⁰⁴ The court distinguished the invasiveness of the near-perpetual tracking in Carpenter and Leaders of a Beautiful Struggle with Norfolk’s ALPR system, because the 176 ALPR cameras are not continuous and “ha[ve] many thousands more blind spots than it has ‘unblinking eyes.'”¹⁰⁵

Plaintiffs appealed and filed their opening brief on April 13, 2026, two weeks before the Chatrie decision was issued. One month after Chatrie was decided, Plaintiff-Appellants filed their reply brief, in which they argue that “Chatrie renders [Norfolk’s arguments] untenable.”¹⁰⁶ They characterize Chatrie as reinforcing Carpenter‘s history-based guideposts and clarifying that Carpenter did not establish a quantitative test.¹⁵

In response to Norfolk’s argument that its ALPR system does not follow people into private places, Plaintiff-Appellants argue that “Chatrie clarified that surveillance of movements” can invade into “private matters” by revealing “(i) ‘repeated patterns’ and (ii) visits to sensitive locations.”¹⁰⁷ In this case, Plaintiff-Appellants argue that Norfolk’s ALPR system is capable of revealing both.¹⁰⁸

Further, Plaintiff-Appellants dispute Norfolk’s argument that Chatrie distinguished between technology that only tracks public movements (like ALPRs) and cell-phone tracking technology.¹⁰⁹ Chatrie, they respond, confirmed that “‘even short-term monitoring of a person’s physical movements’ can effect a Fourth Amendment search” by revealing trips to sensitive locations and that Chatrie “did not disturb Beautiful Struggle‘s holding that multi-day public surveillance can reveal intimate details through pattern-based deductions.”¹¹⁰

Plaintiff-Appellants also invoke Chatrie to urge the Fourth Circuit to “focus on the [ALPR system’s] capabilities, not just what [it] capture[d] about a given person at a given time.”¹¹¹ Notably, they characterize the Chatrie Court as “focus[ing] solely on what police might do with Location History” and rejecting the government’s argument that what Location History could reveal or enable police to do should not inform the analysis because they were not implicated by the facts of Chatrie.¹¹²

In response to Norfolk’s emphasis on gaps in the ALPR system’s coverage, Plaintiff-Appellants argue that the “Supreme Court expressly held that quantity is not dispositive.”¹¹³

Ultimately, the Fourth Circuit’s resolution of these arguments may provide further guidance on how Chatrie applies to ALPR surveillance, making this case one to follow.

On the other side of the ALPR debate, Flock, a primary producer of ALPR cameras, argues that Chatrie “did not disturb the extensive, uniform body of precedent distinguishing fixed public-road cameras from comprehensive cellphone tracking.”¹¹⁴ For Flock, Chatrie‘s relevance to ALPR technology comes in the form of “reinforc[ing] the longstanding distinction between comprehensive digital tracking of people and technologies like ALPR that observe intermittent locations of vehicles on public roads.”¹⁵

Future challenges will likely depend on how comprehensive and connected the ALPR system is.¹¹⁵ “‘If the technology evolves’ to engender surveillance capabilities comparable to those in Carpenter, ‘then perhaps in the future a warrant may be required.'”¹¹⁶ If ALPR systems become sufficiently similar to the aerial surveillance in Beautiful Struggle which created a type of virtual panopticon such that individuals were constantly surveilled, similar constitutional challenges may follow. For litigants, “[t]his demonstrates the importance of fully developing the record as to how many cameras feed into the database system and how many hits exist for the license plate in question.”¹¹⁷ As camera density increases, data retention periods expand, and artificial intelligence improves vehicle identification, Chatrie‘s “virtual panopticon” and the mosaic theory may provide a path forward for litigants to challenge expanding ALPR systems.

b. Facial Recognition Technology, Cameras, & Artificial Intelligence

Another increasingly prevalent investigative tool is facial recognition technology (“FRT”). FRT is “a type of biometric technology designed to identify or verify an individual by analyzing unique and measurable facial features.”¹¹⁸ Although FRT can be considered similar to DNA testing and fingerprinting, more complex privacy implications can arise when FRT is combined with widespread camera networks like ALPRs or pole cameras and artificial intelligence (“AI”) that can track individuals over extended periods of time.¹¹⁹

When courts consider limited uses of FRT, they are generally viewed as permissible. For example, in United States v. Ostein, the district court found that law enforcement’s use of Clearview AI did not violate the Fourth Amendment when it searched publicly accessible websites because “the defendant did not have an objectively reasonable expectation of privacy in publicly posted images of himself.”¹²⁰ Similarly, in People v. Reyes, a New York court declined to preclude testimony concerning the results of the police’s use of FRT to generate an investigative lead of the perpetrator’s identity from security video stills because officers independently identified the defendant after further investigation.¹²¹ The court distinguished between admitting the results of FRT as evidence of a defendant’s identity at a criminal trial and the use of FRT “as tools for identifying or eliminating suspects” during an investigation.¹²²

However, in instances where law enforcement uses FRT alongside widespread camera networks and/or AI, Chatrie‘s virtual panopticon concern intensifies. If the courts are concerned about aggregating data and the inferences that can be drawn from that aggregation, then AI-enabled, widespread visual surveillance may raise significant Fourth Amendment concerns.

In the context of visual surveillance, the Massachusetts Supreme Judicial Court held that, under the Massachusetts Constitution, pole-camera surveillance of a residence for two months violated reasonable expectations of privacy and thus was a search.¹²³ Although most courts conclude that pole camera surveillance does not infringe on any reasonable expectation of privacy because it is in public view,¹²⁴ not all courts agree.¹²⁵ The Court wrote that “[w]hile people subjectively may lack an expectation of privacy in some discrete actions they undertake in unshielded areas around their homes, they do not expect that every such action will be observed and perfectly preserved for the future.”¹²⁶

But in United States v. Tuggle, the Seventh Circuit concluded that eighteen months of camera surveillance around the defendant’s home were “not a search under the mosaic theory,” even if one were to accept that the mosaic theory was the correct test to apply.¹²⁷ Compared to the near-continuous surveillance in Carpenter, the cameras “exposed no details about where Tuggle traveled, what businesses he frequented with whom he interacted in public, or whose homes he visited, among many other intimate details of his life.”¹⁵ Thus, this surveillance did not show the “whole of his physical movements.”¹²⁸ But, even in holding that this surveillance was not a search, the Court expressed “unease about the implications of that surveillance for future cases” and concern “that technological growth will predictably have an inverse and inimical relationship with individual privacy from government intrusion.”¹²⁹

Looking forward, the central issue is the future of precision. As systems integrate more AI functions, and expand their networks, they will become better equipped to recognize more and more people. The more that law enforcement can increase precision, the more that individual and exacting data points can be strung together to deduce the whole of a person’s movement. Additionally, as with other technologies, targeted use to identify a suspect is often different from consistent use over a whole area and capturing those who are not suspected of a crime. The former resembles traditional, particularized surveillance, but the latter risks the kind of dragnet surveillance that Chatrie, Carpenter, and Leaders of a Beautiful Struggle caution against.

c. Reverse Keyword Warrants: Browser Searches & AI Chatbot Conversations

In a reverse keyword search warrant, law enforcement compiles a “list of words or phrases that relate to some criminal activity and submit the terms to a search engine provider.”¹³⁰ The provider then “pulls data on everyone who searched a specific set of keywords, and using that data, [police] work[s] backwards to investigate leads or suspects.”¹³¹ Like a geofence warrant, this investigation begins not with a particularized suspect, but with a digital dataset containing information about numerous unknown individuals. Generally, the reverse warrant identifies everyone who was interested in a specific topic.

The Colorado Supreme Court addressed reverse keyword warrants in People v. Seymour. There, police obtained a warrant requiring that Google produce a list of devices and their IP addresses “for any Google accounts that searched the address [of an arson] during the fifteen-day period before the fire while using Google Services (i.e., Google Chrome, Google Maps, or any other Google service).”¹³² Google produced a spreadsheet of eight accounts.¹⁵ For the five of the eight accounts that had Colorado IP addresses, police requested names and other identifying information from Google.¹⁵ Police eventually identified and charged the defendant.¹⁵ The Court concluded that the defendant had a reasonable expectation of privacy under the Colorado Constitution, as he “was ‘entitled to assume that’ his search history would ‘not be broadcast to the world.'”¹³³ At the same time, however, the Seymour Court noted that “most federal courts reject the notion that an individual such as [the defendant] has a reasonable expectation of privacy in information shared with a third-party vendor.”¹⁵

The Pennsylvania Supreme Court has reached that opposite conclusion. In Commonwealth v. Kurtz, police obtained a reverse keyword search warrant for anyone who had searched the victim’s name or address in the week preceding her assault.¹³⁴ The Court applied the “traditional third-party doctrine,” finding that the defendant lacked a reasonable expectation of privacy in his searches because Google informs users that it will collect and store search records and could disclose them in legal proceedings.¹³⁵ Additionally, the Court distinguished Carpenter‘s involuntary use of cellphones, where one cannot help but leave a trail of data, to the voluntary use of the internet.¹³⁶

After Chatrie, courts may consider whether people believe their Google searches to be their own. Does our search history sufficiently resemble our “emails, documents, photographs, or calendars” that are accessible on our devices and we view as our own, even if additionally stored on Google’s servers?⁷⁰ Is search history different from cell phone location tracking because creating a search is considered a more voluntary and affirmative action, despite search engines’ prevalence in modern society? Or does search history contribute to a mosaic, revealing individuals’ medical concerns, political beliefs, financial circumstances, and more?

These questions become more significant as traditional internet searches yield to AI. The U.S. Department of Homeland Security (“DHS”) served OpenAI with a reverse warrant, requesting information to help identify an individual who had entered certain ChatGPT prompts, while investigating child exploitation.¹³⁷ This was the “first known federal search warrant asking OpenAI for user data.”¹⁵ Although these warrants are relatively new and have received little judicial consideration, they illustrate a potentially even more invasive form of law enforcement investigation. Unlike conventional search engines, which record the search, generative AI systems capture interactive conversations. Chatbots are designed to do more than “just receive the thoughts of the user.”¹³⁸ They are “designed to adapt to them, elicit them, and anticipate them,” often encouraging “private disclosures.”¹⁵ These exchanges can mimic personal, private conversations, more than traditional internet searches. Further, people are increasingly involving chatbots in intimate topics, using them as “financial advisors; doctors; lawyers; spiritual advisors; companions and confidants; role-players and fantasy facilitators; and more.”¹⁵ Thus, these conversations have the potential to reveal even more than a typical search, making reverse keyword warrants directed to generative AI servicers potentially far more invasive than those directed at Google and other search engines.

Ultimately, in using reverse keyword warrants, the same concerns underlying Chatrie, including aggregation of highly revealing data, retrospective surveillance, and declining relevance of the third-party doctrine, are important to keep in mind.

d. Other Applications

Other surveillance technologies may raise similar questions. Consider, for example, challenges to tower dumps¹³⁹ and wearable device data.¹⁴⁰ Although these technologies collect different types and quantities of data, each may require courts to confront similar questions about the revealing nature of their surveillance. The examples discussed in this article are by no means exhaustive, as emerging technologies that identify individuals from a broad pool of information and provide consistent surveillance implicate the same concerns underlying Chatrie.

V. Conclusion

The uncertainty brought by technology is not new. In 2001, the Supreme Court warned that Fourth Amendment protections cannot be left “at the mercy of advancing technology.”¹⁴¹ For many, that concern has become increasingly prevalent.

As the lower courts confront the aftermath of Chatrie, litigants are likely to raise similar questions in challenges to government use of other surveillance technologies. Arguments may sound in the mosaic theory, focusing on what the government can learn by aggregating many pieces of information and whether that aggregation creates a virtual panopticon. Arguments may also focus on whether individuals reasonably believe that information is their own. At the same time, law enforcement will urge courts to consider the practical value of these technologies and emphasize that collecting discrete pieces of information does not necessarily amount to comprehensive surveillance. They will also likely invoke the third-party doctrine where it remains applicable.

How those arguments fare will likely depend heavily on the factual record in each case. For example: How many cameras were in the area? How many hours were the cameras running? How long was the data retained? How easily can the data points be strung together to reconstruct the whole of a person’s movements? Was data voluntarily shared with a third party?

Chatrie does not necessarily answer questions regarding advancing technologies. But it provides a framework through which courts and litigants will confront emerging Fourth Amendment questions, balancing utility in investigation with individual privacy concerns. Moving forward, Chatrie‘s concerns will continue to be important to consider when the government employs digital surveillance, especially where aggregated data can create a detailed picture of an individual’s life.

Endnotes

1. 609 U.S. ___ (2026), No. 25-112, slip op. at 2 (U.S. June 29, 2026). [↩]
2. 585 U.S. 296 (2018). [↩]
3. United States v. Jones, 565 U.S. 400, 416 (2012) (Sotomayor, J., concurring) (quoting United States v. Cuevas-Perez, 640 F.3d 272, 285 (7th Cir. 2011) (Flaum, J., concurring) ). [↩]
4. See Nicole Ezeh et al., Artificial Intelligence and Law Enforcement: The Federal and State Landscape, Nat’l Conf. State Legislatures (Feb. 3, 2025) (summarizing how state and local law enforcement are using AI and state and federal actions around the issue), https://www.ncsl.org/civil-and-criminal-justice/artificial-intelligence-and-law-enforcement-the-federal-and-state-landscape. [↩]
5. U.S. Const. amend. IV. [↩]
6. See Katz v. United States, 389 U.S. 347, 350-51 (1967); Chatrie, slip op. at 10 (Alito, J., dissenting) (In Katz, the “Court expanded its Fourth Amendment doctrine to protect more than the physical security of one’s person and property.”). [↩]
7. 389 U.S. at 351. [↩]
8. Id. at 360 (Harlan, J., concurring). [↩]
9. Id. at 361 (Harlan, J., concurring). [↩]
10. Id. (Harlan, J., concurring). [↩]
11. Chatrie, slip op. at 10 (Alito, J., dissenting). [↩]
12. Id. at 24 (alteration in original) (quoting United States v. Miller, 425 U.S. 435, 435 (1976) ). [↩]
13. Miller, 425 U.S. at 443. [↩]
14. 442 U.S. 735, 744 (1979). [↩]
15. Id. [↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩]
16. See Carpenter, 585 U.S. at 298 (“This decision . . . does not disturb the application of Smith and Miller.”); Chatrie, slip op. at 25 (noting that “[t]here is a ‘world of difference’ between the ‘exhaustive chronicle of location information casually collected by wireless carriers’ and ‘the limited types of personal information addressed in Smith and Miller” (quoting Carpenter, 585 U.S. at 309) ). [↩]
17. Id. at 3 (Gorsuch, J., concurring in the judgment). [↩]
18. 565 U.S. 400, 403-04 (2012). [↩]
19. Id. at 409. [↩]
20. Id. at 404. [↩]
21. See id. at 430 (Alito, J., concurring in the judgment) (arguing that the Court should have “ask[ed] whether the use of GPS tracking in a particular case involved a degree of intrusion that a reasonable person would not have anticipated”); id. at 416 (Sotomayor, J., concurring) (noting that she would have “ask[ed] whether people reasonably expect that their movements will be recorded and aggregated in a manner that enables the government to ascertain, more or less at will, their political and religious beliefs, sexual habits, and so on”). [↩]
22. See id. at 414-15 (Sotomayor, J., concurring). [↩]
23. Id. at 420 (Alito, J., concurring in the judgment); id. at 424-35 (Alito, J., concurring in the judgment) (“[T]he Court’s reasoning largely disregards what is really important (the use of a GPS for the purpose of long-term tracking) and instead attaches great significance to something that most would view as relatively minor (attaching to the bottom of a car a small, light object that does not interfere in any way with the car’s operation).”). [↩]
24. Id. at 415 (Sotomayor, J., concurring) (quoting People v. Weaver, 909 N.E.2d 1195, 1199 (N.Y. 2009) ). [↩]
25. See Chatrie, slip op. at 20 (reproducing the quotation); Carpenter, 585 U.S. at 311 (observing that “the time-stamped data 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'” (quoting Jones, 565 U.S. at 415 (Sotomayor, J., concurring) ). [↩]
26. Robert Fairbanks, Masterpiece or Mess: The Mosaic Theory of the Fourth Amendment Post-Carpenter, 26 Berkley J. Crim. L. 71, 74 (2021); see also Orin S. Kerr, The Mosaic Theory of the Fourth Amendment, 111 Mich. L. Rev. 311, 320 (2012) (“Instead of asking if a particular act is a search, the mosaic theory asks whether a series of acts that are not searches in isolation amount to a search when considered as a group. The mosaic theory is therefore premised on aggregation: it considers whether a set of non-searches aggregated together amount to a search because their collection and subsequent analysis creates a revealing mosaic.”) [↩]
27. 573 U.S. 373 (2014). [↩]
28. Id. at 401. [↩]
29. Id. at 385. [↩]
30. 585 U.S. at 315. [↩]
31. Id. at 310. [↩]
32. Id. at 315. [↩]
33. Id. (quoting Riley, 573 U.S. at 387). [↩]
34. Id. at 311. [↩]
35. Id. at 311-12. [↩]
36. Id. at 320. [↩]
37. Fairbanks, supra note 26, at 73. [↩]
38. Matthew Tokson, The Carpenter Test as a Transformation of Fourth Amendment Law, 2023 U. Ill. L. Rev. 507, 518 (2023). [↩]
39. Jim Dempsey, Beyond Carpenter — A Legislative Framework for Mobile Location Privacy, Lawfare (Mar. 6, 2026) https://www.lawfaremedia.org/article/beyond-carpenter—a-legislative-framework-for-mobile-location-privacy. [↩]
40. Jake Laperruque, A Fork In the Road for the Fourth Amendment: How the Chatrie Case Could Shape Location Surveillance and Reverse Warrants for the Digital Age, Ctr. for Democracy & Tech. (Apr. 23, 2025), https://cdt.org/insights/a-fork-in-the-road-for-the-fourth-amendment-how-the-chatrie-case-could-shape-location-surveillance-and-reverse-warrants-for-the-digital-age/. [↩]
41. Chatrie, slip op. at 1. [↩]
42. Id. at 6 n.3. [↩]
43. Brief for Google LCC as Amici Curiae Supporting Neither Party at 12, No, 25-112, Chatrie v. United States, 609 U.S. ___ (2026). [↩]
44. Laperruque, supra note 41. [↩]
45. Chatrie, slip op. at 6. [↩]
46. Id. at 7-8. [↩]
47. Id. at 8. [↩]
48. Id. at 10-11. [↩]
49. Id. at 11. [↩]
50. Id.; see United States v. Chatrie, 136 F.4th 100, 101 (4th Cir. 2025) (en banc) (writing that “[t]he judgment of the district court is AFFIRMED.”). [↩]
51. Chatrie, slip op. at 16. [↩]
52. Id. (quoting Carpenter, 585 U.S. at 312). [↩]
53. Id. at 17 (citing Carpenter, 585 U.S. at 302). [↩]
54. Id. at 15 (quoting Carpenter, 585 U.S. at 311-12). [↩]
55. Id. at 18. [↩]
56. Id. (quoting Carpenter, 585 U.S. at 305). [↩][↩]
57. Id. at 20. [↩]
58. Id., slip op. at 20 (quoting Pa. Coal Co. v. Mahon, 260 U.S. 393, 415 (1922) ). [↩]
59. Id., slip op. at 21. [↩]
60. Id., slip op. at 20 (quoting Kyllo v. United States, 533 U.S. 27, 37 (2018). [↩]
61. The panopticon was a circular prison designed by the English philosopher Jeremy Bentham in the 18th century where the design allowed one officer to watch every inmate without the inmates knowing whether they are being observed. [↩]
62. Chatrie, slip op. (emphasis added). [↩]
63. Michael Leahy, The Ground Shifts: Chatrie‘s Impact on Data Governance Beyond the Fourth Amendment, Int’l Ass’n Priv. Pros. (July 6, 2026) https://www.iapp.org/news/a/the-ground-shifts-chatries-impact-on-data-governance-beyond-the-fourth-amendment. [↩]
64. Chatrie, slip op. at 25. [↩]
65. Id., slip op. at 25. [↩]
66. Id., slip op. at 26, 28. [↩]
67. Id., slip op. at 28. [↩]
68. Leahy, supra note 73. [↩]
69. Daniel Solove, Is the Fourth Amendment Third Party Doctrine Dead?, Substack (Jul. 1, 2026), https://danielsolove.substack.com/p/is-the-fourth-amendment-third-party. [↩]
70. Chatrie, slip op. at 18. [↩][↩]
71. Whitney Russell et al., The Fourth Amendment Moves to the Cloud: Chatrie v. United States and the Future of Digital Privacy, Wilmer Cutler Pickering Hale & Door LLP (July 2, 2026), https://www.wilmerhale.com/en/insights/client-alerts/20260702-the-fourth-amendment-moves-to-the-cloud. [↩]
72. Id., slip op. at 33 (quoting Olmstead v. United States, 277 U.S. 438, 478 (1928) (Brandeis, J., dissenting). [↩]
73. Chatrie, slip op. at 10. [↩]
74. Id., slip op. at 1 (Jackson, J., concurring). [↩]
75. Id. (Jackson, J., concurring). [↩][↩]
76. Id. (Jackson, J., concurring) (citation omitted). [↩]
77. Id., slip op. at 1-2 (Jackson, J., concurring). [↩]
78. See generally United States v. Leon, 468 U.S. 897 (1984) (establishing the good-faith exception to the exclusionary rule, under which evidence obtained in reasonable, good-faith reliance on a search warrant that is subsequently invalidated is generally admissible). [↩]
79. Schmidt v. City of Norfolk, 819 F. Supp. 3d 492, 505 (E.D. Va. 2026). [↩]
80. Data Driven: What is ALPR?, Electronic Frontier Foundation, https://www.eff.org/pages/what-alpr. [↩]
81. Hasan Shahid et al., Automated License Plate Readers: Market Survey, U.S. Dep’t of Homeland Sec., Sci. & Tech. Directorate, Nat’l Urban Sec. Tech. Lab., 1 (2025), https://www.dhs.gov/sites/default/files/2025-06/25_0606_st_lprmsr.pdf. [↩]
82. What is ALPR?, supra note 95. [↩][↩]
83. Ángel Díaz & Rachel Levinson-Waldman, Automatic License Plate Readers: Legal Status and Policy Recommendations for Law Enforcement Use, Brennan Center for Justice (Sep. 10, 2020), https://www.brennancenter.org/our-work/research-reports/automatic-license-plate-readers-legal-status-and-policy-recommendations. [↩]
84. Díaz & Levinson-Waldman, supra note 98. [↩][↩]
85. Dave Maass & Beryl Lipton, Data Driven: Explore How Cops Are Collecting and Sharing Our Travel Patterns Using Automated License Plate Readers, Electronic Frontier Foundation, https://www.eff.org/pages/automated-license-plate-reader-dataset. [↩]
86. Dave Maass, Data Driven 2: California Dragnet—New Data Set Shows Scale of Vehicle Surveillance in the Golden State, Electronic Frontier Foundation (Apr. 22, 2021), https://www.eff.org/deeplinks/2021/04/data-driven-2-california-dragnet-new-dataset-shows-scale-vehicle-surveillance. [↩]
87. Maass & Lipton, supra note 101; see also id. (noting that “99.5% of the [2.5 billion] license plates scanned” between 2016-2017 “were not under suspicion at the time the vehicles’ plates were collected); Maass, supra note 102 (noting that 99.9% of the “more than 1 billion license plate scans” in 2019, were “not actively related to an investigation when it was collected”). [↩]
88. Megan Brenan, 83% of U.S. Adults Drive Frequently; Fewer Enjoy It a Lot, Gallup (July 9, 2018), https://news.gallup.com/poll/236813/adults-drive-frequently-fewer-enjoy-lot.aspx. [↩]
89. California v. Carney, 471 U.S. 386, 392 (1985). [↩]
90. United States v. Knotts, 460 U.S. 276, 281 (1983). [↩]
91. Chatrie, slip op. at 22 (distinguishing surveillance on public roads in Knotts from “movements that Location History reveals are not limited public streets”). [↩]
92. 585 U.S. at 316. [↩]
93. United States v. Ellison, 462 F.3d 557, 561 (6th Cir. 2006), cert. denied, 552 U.S. 947 (2007); see also United States v. Diaz-Castaneda, 494 F.3d 1146, 1152 (9th Cir. 2007) (holding that “when officers see a license plate number in plain view, and then use that plate to access additional non-private information about the car and its owner, they do not conduct a Fourth Amendment search”); Becerra v. City of Albuquerque, No. 23-2053, 2023 WL 7321633, *2 (10th Cir. Nov. 7, 2023) (“Because [the defendant] had no expectation of privacy in his license plate information, the officers did not conduct a Fourth Amendment ‘search’ by examining it.”); United States v. Mansur, 375 Fed. Appx. 458, 461 n.3 (6th Cir. 2010), cert. denied, 560 U.S. 948 (2010) (“The officers use of the information on [the defendant’s] license plate did not violate the Fourth Amendment.”); United States v. Sturdivant, 786 F. Supp. 3d 1098, 1109 (N.D. Ohio 2025) (“Objectively, it is not reasonable to have an expectation of privacy in a license plate or temporary tag, which the law requires to be visible on the outside of a car.”). [↩]
94. See Rinaldi v. Sylvester, 2025 WL 2682691, *17 (S.D.N.Y. Sept. 19, 2025) (noting that “nearly every court” that has addressed the issue has “held that queries of [A]LPR databases do not constitute Fourth Amendment searches”). [↩]
95. See, e.g., id.; Sturdivant, 786 F. Supp. 3d at 1108-09. [↩]
96. 819 F. Supp. 3d 492, 498 (E.D. Va. 2026). [↩]
97. Id. at 496-97. [↩]
98. See Schmidt, 819 F. Supp. 3d at 509. [↩]
99. 2 F.4th 330, 334 (4th Cir. 2021). [↩]
100. Id. (citation omitted). [↩]
101. Id. at 341 (quoting Carpenter, 585 U.S. at 312). [↩]
102. Id. at 342 (quoting Carpenter, 585 U.S. at 311). [↩]
103. Brief of Petitioner-Appellant at 15, Schmidt v. United States, No. 26-1227 (4th Cir. Apr. 13, 2026). [↩]
104. Schmidt, 819 F. Supp. 3d at 511. [↩]
105. Id. at 512. [↩]
106. Reply Brief of Petitioner-Appellant at 2, Schmidt v. United States, No. 26-1227 (4th Cir. July 23, 2026). [↩]
107. Id. at 10 (quoting Chatrie, slip op. at 20) (cleaned up). [↩]
108. Id. at 11-13. [↩]
109. Id. at 13. [↩]
110. Id. at 13-14. [↩]
111. Id. at 3-4. [↩]
112. Id. at 14. [↩]
113. Id. at 5; see also id. at 22-23 (“Chatrie foreclosed Norfolk’s argument that Carpenter set a quantitative threshold that requires a surveillance technology to capture the literal ‘whole’ of people’s movements to qualify as a search.”). [↩]
114. Michael Goldsticker, What the Supreme Court’s Chatrie Decision Means for ALPR Technology, The Flock Safety Blog (July 9, 2026), flocksafety.com/blog/what-the-supreme-courts-chatrie-decision-actually-means-for-alpr-technology. [↩]
115. See Rinaldi, 2025 WL 2682691 at *18 (“[T]he Court does not intend to suggest that the use of [A]LPRs can never violate the Fourth Amendment. It is possible that a ‘more extensive network of [ALPRs] might infringe a reasonable expectation of privacy under Katz.'” (quoting Scholl v. Ill. State Police, 766 F. Supp. 3d 701, 721 (N.D. Ill. Mar. 31, 2025) ); Schmidt, 819 F. Supp. 3d at 497 (“[S]everal federal judges . . . have expressly cautioned that their rejection of a constitutional challenge to the use of ALPR technology should not be indiscriminately extended because, as the number and capabilities expand, the constitutional balancing could conceivably tip the other way.”). [↩]
116. Sturdivant, 786 F. Supp. 3d at 1113-14 (quoting United States v. Yang, 858 F.3d 851 (9th Cir. 2020) (Bea, J., concurring) ). [↩]
117. Fairbanks, supra note 26, at 106. [↩]
118. Dominique T. Greene-Sanders, Facial Recognition Technology: Definitions, Applications, and Policy Considerations for Congress, Library of Congress (May 4, 2026), https://www.congress.gov/crs-product/R48935. [↩]
119. See Emelie Stiernstromer, Facial Recognition Technology in Law Enforcement — A Scoping Review of Existing Empirical Studies, Police Prac. & Rsch, 2 (Feb. 12, 2026) (“As part of a broader suite of surveillance tools (including CCTV [closed-circuit television], automated license plate readers (ALPR), and body-worn cameras (BWC) ) FRT, a biometric system comparable to fingerprinting and DNA analysis, enables the identification or verification of individuals.”); Clearview AI, https://www.clearview.ai/ (“Clearview AI’s highly accurate facial recognition platform” is “helping law enforcement to rapidly generate leads to identify suspects, witnesses, and victims,” with more than 70 billion images in its law enforcement database.). [↩]
120. 2025 WL 3299427, *3 (M.D. Tenn. Nov. 26, 2025). [↩]
121. 133 N.Y.S.3d 433 (Oct. 7, 2020). [↩]
122. Id. at 436-37. [↩]
123. Commonwealth v. Mora, 150 N.E.3d 297, 312-13 (Mass. 2020). [↩]
124. Id. at 304 (collecting cases). [↩]
125. Id. (collecting cases). [↩]
126. Id. at 306. [↩]
127. 4 F.4th 505, 523 (7th Cir. 2021). The Seventh Circuit explicitly declined to adopt the mosaic theory. Id. at 524 (“Even if we accepted the mosaic theory, however—and we do not go that far—current Supreme Court precedent does not support Tuggle’s argument.”) [↩]
128. Id. (quoting Carpenter, 585 U.S. at 310). [↩]
129. Id. at 526, 528. [↩]
130. Brief for Eight Law Professors as Amici Curiae Supporting Petitioner, Chatrie v. United States, 609 U.S. ___ (2026) (No. 25-112). [↩]
131. Reverse Search Warrants, Nat’l Ass’n Crim. Def. Laws., https://www.nacdl.org/Landing/Reverse-Search-Warrants (last visited July 31, 2026). [↩]
132. People v. Seymour, 536 P.3d 1260, 1269 (Colo. 2023) (cleaned up). [↩]
133. Id. at 1271-72 (quoting People v. Gutierrez, 222 P.3d 925, 932 (Colo. 2009) ). [↩]
134. 348 A.3d 133, 139 (Pa. 2025). [↩]
135. Id. at 151-52, 153. [↩]
136. Id. at 149 (“[U]nlike smart phones, the internet is not a ‘feature of human anatomy.’ The use of the internet is not involuntary, as cell phones have become. To the contrary, every time a person logs on to the internet, that person makes a choice. She chooses to input data into a network owned and operated by an internet service provider.” (quoting Riley, 573 U.S. at 385) ). [↩]
137. Thomas Brewster, DHS Ordered OpenAI to Share User Data in First Known Warrant for ChatGPT Prompts, Forbes (Oct. 20, 2025), https://www.forbes.com/sites/thomasbrewster/2025/10/20/openai-ordered-to-unmask-writer-of-prompts/. [↩]
138. Brief for Eight Law Professors as Amici Curiae Supporting Petitioner, at 14, supra n. 154. [↩]
139. A tower dump generally refers to law enforcement’s use of records identifying devices that connected to a cell tower during a period of time. For a discussion of tower dumps after Carpenter, see Emma Lux, Privacy in the Dumps: Analyzing Cell Tower Dumps Under the Fourth Amendment, available at https://www.law.georgetown.edu/american-criminal-law-review/wp-content/uploads/sites/15/2020/05/57-4-Lux-Privacy-in-the-Dumps.pdf. [↩]
140. A wearable device, such as an Apple Watch or Fitbit, tracks personal health information. For a discussion on wearable devices, see Maggie Dowdy, How the Government Accesses Your Personal Health Data with this One Simple Trick, 114 KY. L. J. Online (2025), available at https://www.kentuckylawjournal.org/blog/how-the-government-accesses-your-personal-health-data-using-this-one-simple-trick. [↩]
141. Kyllo v. United States, 533 U.S. 27, 35 (2001). [↩]