ALPR Mass Surveillance as a Matter of Privacy

-- By NelsonHua - 16 May 2015

As of 2012, approximately 71% of United States police departments utilized some form of automatic license plate recognition (ALPR) software. While such software might be an effective tool in identifying and recovering stolen vehicles, the capture, analysis, and storage of such data presents serious privacy concerns. In fact, the ways in which ALPR is used by local police departments are likely unconstitutional. In any event, state policymakers and Congress should impose regulatory limits to the usage of ALPR.

The Technology

Essentially, ALPR is a combination of image processing and optical character recognition software (OCR). The software identifies and isolates the presence of a license plate on a photograph, normalizes the exposure on the plate, segments individual characters, and then identifies the characters through OCR. Images are typically obtained either through stationary, perhaps hidden, cameras or cameras mounted on police vehicles.

Local police departments then cross-reference the data with databases for stolen vehicles and individuals with outstanding warrants, for instance. Such uses are less controversial, but only account for a small fraction of recorded scans. (For example, 7,244 hits out of 7.3 million records in Seattle) What is more questionable, however, is that the data can be stored indefinitely. Some departments store the information for years, allowing for the use of the location data of individuals, who were not subjects of an investigation at the time of capture, as evidence in criminal cases. Such stored records, with scans numbering in the billions amount to comprehensive databases of individuals’ whereabouts, subject to use by law enforcement and even private actors that are willing to pay the right price to the providers of the software.

The Legal Ramifications

At the most superficial level, the process poses no particular problems. License plate numbers are public information. Likewise, there are no particular legal problems with taking photographs in public places. However, it is problematic when the process generates stored records of individuals’ whereabouts, particularly for investigatory use when there is no actual ongoing investigation.

This practice has recently been challenged in various ways. In 2013, the Electronic Frontier Foundation (EFF) and the ACLU of Southern California filed suit against the Los Angeles County Sheriff’s Department under the California Public Records Act after the department refused to release such stored ALPR data. Although the department prevailed in the lower court, EFF appealed and argued for accountability over the process in the California Court of Appeals this past March. On May 6, the ACLU of Virginia filed suit on behalf of a Virginia man alleging that the Fairfax County Police Department’s collection and storage of his license plate data violates the state’s Government Data Collection and Dissemination Practices Act, a position that the Virginia Attorney General issued an advisory opinion espousing in 2013. Additionally, Virginia’s lawmakers have been contemplating further legislation limiting ALPR use for mass surveillance.

In fact, the practice might actually be an unconstitutional invasion of privacy. It is often justified through United States v. Knotts, 460 U.S. 281, unanimously decided in 1983, which held that “[a] person traveling in an automobile [in public] has no reasonable expectation of privacy.” However, in United States v. Jones, 132 S. Ct. 945, writing for a unanimous bench, Justice Alito noted that extensively and “secretly monitoring and cataloging” car movements for a “very long time” might violate a reasonable expectation of privacy. Though this language is dicta in a case about warrantless GPS tracking, it suggests that if the issue of ALPR surveillance were to rise to the level of the Supreme Court, the Court might very well partially reverse Knotts or limit it to its facts and find the practice unconstitutional. Individual instances of tracking as part of an ongoing investigation, as was the case in the facts of Knotts, might not violate the constitutional right to privacy, but surveillance in the absence of an investigation, which was not possible at the time Knotts was decided, likely does. As surveillance becomes more and more comprehensive, it is more likely to violate a reasonable expectation of privacy. Common ALPR practices likely cross this jurisprudential threshold.

Nonetheless, Congress and state legislatures should pass bills limiting the use of ALPR for mass surveillance. Every day, millions of scans are recorded nationwide. The legislative response has been virtually nonexistent. Although the International Association of Chiefs of Police (IACP) fears it, no one has yet to propose such a bill in Congress. The Virginia bill originally proposed a storage limit of seven days for passively collected scans, but gubernatorial amendments have suggested that this be expanded to sixty days and that the bill allow for dissemination to other agencies without limit.”

An appropriate bill, whether at the state or federal level, should entirely disallow the storage of passively collected scans; though, a limit such as the originally proposed seven days in Virginia might be more politically practicable. Additionally, the bill should ensure disclosure of such records under legislation like FOIA to maintain accountability.