A federal judge’s ruling that a police search of a nationwide license plate database violated the Fourth Amendment has added a significant new legal challenge to automated license plate readers as governments across the country reconsider how police may use the increasingly common surveillance systems.
U.S. District Judge Sara E. Hill of the Northern District of Oklahoma ruled that a Tulsa County sheriff’s deputy conducted an unconstitutional warrantless search when he used automated license plate reader systems, including Flock Safety, to reconstruct about a month of a vehicle’s movements. The search produced more than 50 location records from multiple states.
The ruling comes during a week of heightened scrutiny of automated license plate readers, commonly called ALPRs. Members of Congress introduced legislation Thursday that would prohibit federal agencies from using the systems, a Virginia police employee was charged with improper ALPR use, and governments elsewhere imposed new restrictions on how police may search and retain license plate data.
Flock Safety operates a large network of ALPR cameras that photograph passing vehicles and record information that can include license plates, vehicle characteristics, locations, and times. Police can search those records as part of investigations.
The Oklahoma case presents a different constitutional question from whether police may photograph a license plate visible on a public road. Hill considered whether police may search a large collection of those observations to reconstruct someone’s movements without first obtaining a warrant.
The case involved Melisa Kyle, whose vehicle was searched after Tulsa County sheriff’s Deputy Freddie Alaniz began following her Mazda SUV. Hill wrote that the deputy began following it “for no apparent reason other than” its California license plate and then searched ALPR databases.
Those searches produced more than 50 records covering about a month of the vehicle’s movements across several states. Alaniz later stopped Kyle for traffic violations. Police eventually discovered 91 pounds of methamphetamine.
Hill found that the initial traffic stop was valid but that the deputy lacked reasonable suspicion to extend it into a drug investigation. She also concluded that searching the historical ALPR records constituted a Fourth Amendment search that was conducted without probable cause or a warrant.
The judge described the growing network as a form of “indiscriminate mass surveillance” and suppressed evidence obtained after the database search. The decision does not establish a nationwide prohibition on warrantless ALPR searches, and Flock has disputed the ruling.
Courts generally have recognized that motorists have little expectation of privacy in license plates displayed publicly. Hill instead focused on what becomes possible when large numbers of individual observations are stored in a searchable database that can reveal a vehicle’s movements over an extended period.
That distinction could become central to future ALPR cases. A federal appeals court reached a different conclusion earlier this year in a Mississippi case involving a much smaller network. The 5th U.S. Circuit Court of Appeals found that periodic observations from a limited number of license plate cameras did not amount to the comprehensive tracking that would trigger Fourth Amendment protection.
The growing legal debate has reached Congress. Sens. Bernie Sanders of Vermont, Jeff Merkley of Oregon, and Rep. Alexandria Ocasio-Cortez of New York introduced the Ban Flock Act on Thursday. The proposal would prohibit federal agencies from using automated license plate readers or accessing information they collect and would restrict some federal funding to state and local governments that continue using ALPR technology.
The legislation faces uncertain prospects, but concern about ALPR surveillance has crossed political divisions. Republican Sen. Josh Hawley of Missouri has also called for federal restrictions on the technology and is pursuing separate legislation.
At the same time, recent cases of alleged misuse have shifted part of the debate from what officers theoretically could do with ALPR databases to what some users allegedly have done.
A Chesterfield County, Virginia, police intelligence investigator was charged Friday with two counts of improper use of an ALPR system and two counts of computer invasion of privacy. Police said coworkers reported concerns about her use of law enforcement databases and Flock cameras. An audit subsequently uncovered what the department described as suspicious transactions.
Five current or former Indianapolis police officers were also recently accused of improperly using Flock searches to obtain information about people they knew, including spouses or romantic partners. Indianapolis police subsequently strengthened requirements governing access and auditing.
Other governments are responding by limiting retention periods and outside access. San Francisco announced restrictions Sept. 29, reducing routine police access to Flock data from 12 months to 30 days and adding documentation requirements for searches.
Missouri has imposed statewide restrictions requiring most ALPR images and data to be deleted after 30 days unless connected to an active criminal investigation, life-safety emergency or court order. Searches must identify the user and include an active case number or specific law enforcement justification, and agencies must audit use of the systems.
Similar questions have reached Central Ohio. Worthington City Council voted Sept. 21 to stop sharing its Flock data with outside agencies while the city develops additional rules governing the system. Worthington continues operating 14 cameras for its own investigations.
Worthington says only police supervisors and detectives may search its system and that searches must be connected to a law enforcement matter with a case or call-for-service number. Police leadership reviews system use weekly and receives alerts about potentially unusual searches. The city prohibits immigration- and reproductive-related searches.
Before the Sept. 21 suspension, Worthington shared its data only with Ohio law enforcement agencies it individually approved. Federal agencies and departments participating in federal immigration enforcement agreements were not permitted access. City Council is expected to reconsider its data-sharing policy later this year.
The changes occurring around the country raise several questions for communities using ALPR cameras: how long vehicle records should be stored, which agencies should have access, what justification officers must provide before conducting searches, how searches are audited and when police should obtain a warrant.
The Oklahoma ruling adds a larger constitutional question. A camera recording a vehicle passing a single location has generally been treated differently under privacy law than technology that continuously tracks someone’s movements. Large interconnected ALPR databases increasingly allow investigators to assemble many individual observations into a history of where a vehicle has traveled.
The developing legal question is whether the government’s ability to reconstruct that history transforms otherwise public observations into a Fourth Amendment search requiring judicial oversight. For police departments already using Flock, the answer could determine whether searching historical ALPR records remains an ordinary investigative step or sometimes requires a warrant.
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