The Fourth Amendment
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.
Norfolk, VA Fourth Amendment Case Against ALPR Use
Two Norfolk residents are suing the city for the breach of their 4th Amendment right against unreasonble searches. Michael Soyfer of Institute for Justice notes that “These cameras can track people’s every move over a prolonged time period. If the government wants to do that, it should have to get a warrant.”
In a press release dated Feb 6, 2025, Institute for Justice referenced “United States Supreme Court case Carpenter v. United States, which held that using cell phone location data to track someone’s movements is a search that requires a warrant under the Fourth Amendment. Chief Judge Davis [on the Virginia case] wrote, “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.” Chief Judge Davis went on to say, “the complaint alleges facts notably similar to those in Carpenter that the Supreme Court found to clearly violate society’s expectation of privacy: law enforcement secretly monitoring and cataloguing the whole of tens of thousands of individual’s movements over an extended period.”
The common refrain that there is ‘no expectation of privacy in public’ doesn’t reflect nuanced court rulings on the subject, as seen above in Carpenter and other cases. In 2021, the Fourth Circuit held that “constant warrantless aerial surveillance over the entire city of Baltimore was unconstitutional,” according to an IJ case update.
“The Framers enacted the Fourth Amendment to protect individuals and their property from arbitrary government intrusion”
Attorney Robert Frommer, Institute for Justice
Carpenter v. United States (2018)
The Oyez file on Carpenter also describes that “the third-party doctrine applies to voluntary exposure, and while a user might be abstractly aware that his cell phone provider keeps logs, it happens without any affirmative act on the user’s part. Thus, the Court held narrowly that the government generally will need a warrant to access cell-site location information.”
In the Carpenter opinion, the court referenced another case related to use of technology by law enforcement (Kyllo v United States, 2001) in stating that “the rule the Court adopts ‘must take account of more sophisticated systems that are already in use or in development.’”
Connecting to ALPR use
Carpenter shows Court consideration of advanced and advancing technologies, it also distinguishes voluntary sharing of information from data collected by virtue of using a service.
United States v. Jones (2012)
According to this fact sheet on GPS data use in court:
“In United States v. Jones, the FBI attached a GPS tracker to a suspect’s vehicle without a warrant to monitor his movements. The tracker provided location data over 28 days, revealing the suspect’s activities related to drug trafficking.
Outcome: The U.S. Supreme Court ruled that placing a GPS tracker without a warrant violated the suspect’s Fourth Amendment rights. The decision emphasized that tracking someone’s vehicle constitutes a search, which requires judicial approval.
Impact: This case set a critical precedent, limiting law enforcement’s ability to conduct warrantless GPS tracking. It established that using tracking devices to monitor personal movements without proper authorization breaches privacy protections.”
Connecting to ALPR use
Jones references capturing location data over a period of time can constitute a search. The Flock ALPR surveillance system captures similar data. Further, the Flock system can be integrated with other types of surveillance cameras to create an even more total “picture” of someone’s whereabouts.
Further Reading
The Brennan Center for Justice produced a research report on ALPRs that goes into depth on related law.
On United States v. Di Re (1948): “It is said that, if such arrests and searches cannot be made, law enforcement will be more difficult and uncertain. But the forefathers, after consulting the lessons of history, designed our Constitution to place obstacles in the way of a too permeating police surveillance, which they seemed to think was a greater danger to a free people than the escape of some criminals from punishment.” And: “That law enforcement may be made more difficult is no justification for disregarding the constitutional prohibition against unreasonable searches and seizures.”
On Delaware v. Prouse (1979): “An individual operating or traveling in an automobile does not lose all reasonable expectation of privacy simply because the automobile and its use are subject to government regulation.” And: “The State’s interest in discretionary spot checks as a means of ensuring the safety of its roadways does not outweigh the resulting intrusion on the privacy and security of the persons detained. Given the physical and psychological intrusion visited upon the occupants of a vehicle by a random stop to check documents, cf. United States v. Brignoni-Ponce, 422 U. 3. 873; United States v. Martinez-Fuerte, 428 U. S. 543, the marginal contribution to roadway safety possibly resulting from a system of spot checks cannot justify subjecting every occupant of every vehicle on the roads to a seizure at the unbridled discretion of law enforcement officials.”
The Supreme Court has “distinguished limited monitoring from “twenty-four hour surveillance of any citizen in the country,” reserving the question of whether such ‘dragnet type law enforcement practices’ merit the application of different constitutional principles.” See United States v. Knotts (1983).
United States v. Jones (2012): “Inexpensive location tracking “makes available at a relatively low cost such a substantial quantum of intimate information about any person whom the Government, in its unfettered discretion, chooses to track” that it “may ‘alter the relationship between citizen and government in a way that is inimical to democratic society.’”
Carpenter v. United States (2018): “The Court observed that this information could be used to track the minutiae of people’s daily lives. It reasoned that the “depth, breadth, and comprehensive reach” of this data, along with “the inescapable and automatic nature of its collection” by virtue of simply carrying a cell phone, necessitate a warrant supported by probable cause.”
On third-party doctrine: “Under the third-party doctrine, individuals do not have a reasonable expectation of privacy in information they are deemed to have voluntarily handed over to third parties.”
“The Carpenter Court also reasoned that individuals do not truly voluntarily share their location data with wireless carriers; instead, the data is automatically collected simply by possessing a cell phone — a device the Court described as “indispensable to participation in modern society” — and by connecting to a mobile network. Similarly, a majority of Americans rely on driving in order to fully participate in society, and their movements are logged by ALPRs by virtue of simply driving and parking on public roads. Just as the only way to avoid generating [Cell-Site Location Information] would be to turn off a mobile device, the only way to avoid ALPR data collection would be to give up driving altogether or to keep a vehicle away from the range of a license plate reader — an impossible task in many places.”
Connecting to ALPR use
Certainly citizens don’t voluntarily hand over their vehicle location to Flock Safety by merely driving by a camera, especially when they may not know it exists and the police acted to intentionally keep them in the dark.