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  • Aaron Garavaglia

Automatic license plate readers: A growing problem for practitioners

Updated: Oct 18, 2023

The 21st century and its hasty progression of technology has arrived, but not without consequence. A national interest in law enforcement and technology has been reignited since the Department of Justice’s announcement last month that its agencies must obtain a warrant before using a “StingRay” cell-site simulator. Whereas StingRay devices have minimal guidance on their usage, another law enforcement tool growing in popularity – the Automatic License Plate Reader (ALPRs) – lacks clear authority.

Automatic License Plate Readers (ALPRs) represent a new intersection of law enforcement practices and technological advancement and collaboration. ALPRs are an attractive law enforcement tool, especially in a modern era of reduced state and municipal funding levels. Generally, ALPRs are compact devices that may be affixed to any structure or vehicle. From privately-owned garbage trucks to “virtual stakeouts”, local municipalities have taken advantage of ALPRs. ALPRs are used by a number of law enforcement agencies in the Washington, D.C. Metropolitan Area. Locally, a recent case has provided an opportunity for practitioners to challenge the use of ALPRs by municipal authorities.

On May 5th, 2015, the American Civil Liberties Union of Virginia filed suit against the Fairfax County Police Department on behalf of Harrison Neal. Neal is a private individual whose license plate was allegedly scanned twice by the Fairfax County Police Department and stored into a database shared amongst several law enforcement agencies in the Washington, D.C. Metropolitan Area. It is important to understand the plaintiff’s specific argument: the plaintiff in Neal v. Fairfax County Police Department sought an injunction through the Government Data Collection and Dissemination Practices Act against the Fairfax County Police Department to discontinue their “passive” use of ALPRs.

ALPRs are primarily operated in either an “active” or a passive manner. An ALPR is operated in an active manner when it simultaneously scans license plates and cross-references them against a “hot list” created by the Virginia State Police. License plates belonging to vehicles that are missing, stolen, or believed to be involved in a crime are added to the list. Active use is an automated version of the process a police officer conducts when manually entering a license plate number and checking it against a hot list. ALPRs are operated in a passive manner when law enforcement saves data associated with a license plate number – generally the time, location, and plate number itself – into a larger database. Stored license plate data is not necessarily associated with a stolen or missing vehicle, or one believed to be involved in a crime. Among a number of uses, the data may be used to discover trends or create profiles. Whether this data is collected or used is generally decided at a local level.

Virginia and Maryland have different philosophies regarding passive use by ALPRs. Prosecuting practitioners may note that that the plaintiff in Neal does not dispute the active use of ALPRs. ALPRs are actively used by various law enforcement agencies in a diverse variety of manners to great effect throughout the country. Locally, passive use of an ALPR is enabled through Maryland Public Safety Code § 3-509. However, in 2013, Virginia joined a minority of jurisdictions when the Attorney General, Kenneth Cuccinelli, II issued an opinion restricting the use of ALRPs.

Defense practitioners should be aware of the different attitudes and cultures regarding ALRP practices. The California Supreme Court recently granted certiorari to hear American Civil Liberties Union Foundation of Southern California v. Superior Court. In that case, the Court of Appeal for the Second Appellate District of California held that data gathered by ALPRs was exempt from information requests under the California Public Records Act, similar to an exception in Maryland Public Safety code § 3-509. The United States Court of Appeals for the Eighth Circuit in United States v. Williams held that an ALPR match to a hot list provides sufficient reasonable suspicion for the purposes of a traffic stop, as required by the Fourth Amendment. Under these conditions, evidence obtained from a traffic stop enabled by use of an ALPR will generally be admissible, with Virginia and the other minority jurisdictions excepted, regarding the use of ALPRs in a passive manner.

Practitioners should be aware that license plate data may be affixed to a location and time. If obtained by a defense practitioner, such data may be used as evidence to confirm a client’s presence at a particular time and location. Alternatively, such data may provide prosecutors with a portrait of a defendant’s activities and history of travel.

ALPRs remain a difficult issue for criminal law practitioners. It is hopeful that the Supreme Court will provide guidance to prosecutors, defense attorneys, and their clients as the proliferation in ALPR continues to grow.


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