Courts Issue Rulings in Two Cases Challenging Law Enforcement Searches of License Plate Databases

By Jennifer Lynch

This week, the Ninth Circuit Court of Appeals issued an opinion in United States v. Yang, a case challenging the search of an automated license plate reader database under the Fourth Amendment. Although the court, citing EFF’s amicus brief, recognized ALPRs capture massive amounts of data on Americans across the country, it decided not to reach the search issue. Instead it held that because Yang was driving a rental car after his rental agreement ended when the search occurred, he didn’t have the right to challenge the search.

The Ninth Circuit’s decision follows an April opinion from Massachusetts’s highest court in another ALPR case, Commonwealth v. McCarthy. In McCarthy, the court held that, although ALPRs raise clear privacy issues under the Fourth Amendment and Massachusetts’s Article 14, McCarthy hadn’t introduced sufficient facts to show that the search at issue in his case rose to the level of a constitutional violation.

ALPRs are high-speed, computer-controlled camera systems that are attached to vehicles, such as police cars, or can be mounted on street poles, highway overpasses, or mobile trailers. Some models can photograph up to 1,800 license plates every minute; and every week, law enforcement agencies across the country use these cameras to collect data on millions of vehicles. The plate numbers, together with location, date, and time information, are uploaded to central servers, and made instantly available to other agencies. The location data generated by ALPRs is so precise it can place a vehicle in front of a specific home or business, as was the case in Yang, or within a specific lane on a bridge, as in McCarthy. Law enforcement agencies may maintain their own databases of ALPR data or store their data with private companies. In the Yang case, the law enforcement agency didn’t collect its own ALPR data but instead accessed a commercial database that advertises it contains 6.5 billion plates collected both by law enforcement and by private contractors.

EFF, along with the ACLU and several other organizations, filed amicus briefs in both Yang and McCarthy last year, as well as in another case decided on different grounds in the California Court of Appeal, People v. Gonzales. In each of these cases, we argued the Supreme Court’s 2018 opinion in Carpenter v. United States—where the Court held law enforcement must get a warrant to access historical cell site location information (CSLI)—should apply to ALPRs. Like CSLI, the aggregation of ALPR data can paint a picture of where a vehicle and its occupants have traveled, including to sensitive and private places like homes, doctors’ offices, and places of worship. ALPR data collection is detailed and indiscriminate; anyone who drives is likely to have their past locations logged in a database available to police. And, like CSLI databases, ALPR databases facilitate retrospective searches of cars whose drivers were not under suspicion when the plates were scanned.

The McCarthy court adopted many of our arguments. Although the Massachusetts Supreme Judicial Court ultimately ruled against the defendant, the court indicated it might have ruled differently if he had introduced more facts on how Massachusetts collects, stores, and shares license plate data. The court cited both our amicus brief and the California Supreme Court’s opinion in our 2017 ALPR case and clearly understood the privacy implications of ALPR data collection. It noted that ALPRs placed near sensitive locations “can reveal information about an individual’s life and associations” and “allow the police to reconstruct people’s past movements without knowing in advance who police are looking for, thus granting police access to a category of information otherwise and previously unknowable.” The court also noted that, “[w]ith enough cameras in enough locations, the historic location data from an ALPR system in Massachusetts would invade a reasonable expectation of privacy and would constitute a search for constitutional purposes.”

Frustratingly, the Yang court declined to address the application of the Fourth Amendment to ALPR searches, finding instead that Yang lacked standing to challenge the search in the first place. The plate scans at issue were of a rental vehicle that Yang failed to return once his rental period expired. Relying on some minimal evidence that the car rental company may not generally authorize renters to hold onto cars after their rental period is up, the court held that Yang had no expectation of privacy related to the vehicle. But it’s hard to square that conclusion with another recent Supreme Court case, Byrd v. United States. In Byrd, the Court found that a driver who was not authorized to drive a rental car under the terms of the rental agreement could nevertheless challenge a law enforcement search of the car. Despite the obvious relevance of Byrd, the Ninth Circuit in Yang did not even cite the case, let alone try to distinguish its facts. This might be grounds for the defendant to ask the Ninth Circuit to reconsider its ruling.

While we’re disappointed that neither court clearly held ALPR database searches violate the Constitution, we’re heartened that Massachusetts’s highest court left the door open for future cases challenging searches of ALPR databases where the defendant can show evidence that the databases draw on an extensive network of cameras.


As Surveillance Litigation Director, Jennifer Lynch leads EFF’s legal work challenging government abuse of search and seizure technologies through the courts by filing lawsuits and amicus briefs in state and federal courts, including the U.S. Supreme Court, on important issues at the intersection of technology and privacy. Jennifer founded EFF’s Street Level Surveillance Project, which informs advocates, defense attorneys, and decisionmakers about new police tools. In 2017, the First Amendment Coalition awarded her its Free Speech and Open Government Award for her work opening up public access to police surveillance records, and in 2019, the Daily Journal named her to its annual list of Top 100 Lawyers in California. Jennifer has written influential white papers on biometric data collection in immigrant communities and law enforcement use of face recognition. She speaks frequently at legal and technical conferences as well as to the general public on technologies like location tracking, biometrics, algorithmic decisionmaking, and AI, and has testified on facial recognition before committees in the Senate and House of Representatives. She is regularly consulted as an expert on these subjects and others by major and technical news media.

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