License plate readers are important police tool, but hurdles remain, study finds

As part of efforts to promote innovation in law enforcement, many of the first generation license plate reader systems were purchased with federal and state grants. As these funding streams can be inconsistent, law enforcement agencies are -- or will be -- forced to make tough decisions about how to maintain the systems.

Making those decisions will require a clear understanding of the current and potential value of the systems to criminal justice agencies, according to RAND researchers.

"License plate readers are a relatively new technology that can be used to help investigate almost any type of crime," said Keith Gierlack, the study's lead author and a researcher at RAND, a nonprofit research organization. "But there are important issues, particularly about privacy, that must be addressed before this tool can reach its full potential."

Because the systems retain information about every license plate read, privacy advocates say law enforcement agencies could use license plate information to track movement of individuals, even if they are not suspects in a crime.

Key privacy issues facing local departments also include establishing standards about how long to keep information collected by license plate scanners, who in a department has access to the information and the types of investigations where the scanner information should be used, Gierlack said.

Some jurisdictions have adopted policies to retain data for set periods, such as six or 12 months. Legislation was introduced in California to regulate use of the license plate readers and legal decisions in New Hampshire, Maine and Virginia have restricted the technology. But no broadly accepted privacy guidelines have emerged to help guide police agencies that adopt the technology.

License plate readers are fixed or mobile cameras that capture an image of a passing vehicle, compare its license plate against official "hotlists" and alert authorities whether it may be of interest. Surveys have found that as many as 70 percent of local police agencies may be using the technology.

Promoted initially as a tool to assist in fighting auto thefts, the technology can be used in many additional ways that law enforcement agencies only have begun to discover.

Researchers say information collected by the scanners can be used to help track down many kinds of offenders (helping collect infraction fees), and could be used to help identify both crime hotspots and crime trends. In addition, the technology could help test the alibis of criminal suspects and support efforts to combat drug cartels and terrorist groups.

RAND researchers conducted their study by reviewing past research on the technology and conducting in-depth reviews of seven police departments that have adopted the technology. They examined budgeting, manpower and maintenance issues, as well as how the technology is being used to aid police work. Both large and small law enforcement agencies were studied, as well as agencies located along international borders.

RAND researchers found that license plate readers provide the most utility to police if they have access to multiple hotlists and other databases of license plates of interest, including DMV data. The lack of access to some of these hotlists reduces the types of investigations license plate readers can aid. Additionally, mechanisms for sharing license plate reader data between jurisdictions are not always available.

Funding for the study was provided by the Office of Justice Programs at the National Institute of Justice.

The project was conducted within the RAND Safety and Justice Program, which conducts public policy research on corrections, policing, public safety and occupational safety.