The American Civil Liberties Union of Maryland said Monday that it wants to know what police are doing with information collected by automated scanners that routinely read the license plates of drivers throughout the state.

Since at least 2005, "automatic license plate readers" have been recording license plates in Maryland from alongside roads and highways and from inside police patrol cars. For the past six to eight months, data from hundreds of those readers has been fed into a central repository.

On Monday, the ACLU of Maryland asked dozens of local and state police agencies to more fully explain the extent of their use of the readers and how the information they gather is used, shared and stored, said David Rocah, a staff attorney for the organization.

"I think the privacy implications are huge, and there has been virtually zero public discussion," Rocah said.

The ACLU's national office and affiliates in 35 states made similar requests Monday.

"The American people have a right to know whether our police departments are using these tools in a limited and responsible manner, or whether they are keeping records of our movements for months or years for no good reason," Catherine Crump, an ACLU staff attorney, said in a statement.

According to the Governor's Office of Homeland Security, there have been more than 320 readers deployed throughout the state since 2005.

Data from hundreds of those readers has for months been fed into a central repository at the Maryland Coordination and Analysis Center, a law enforcement cooperative created by local, state and federal agencies after the terrorist attacks Sept. 11, 2001.

The readers are used in a variety of ways, from helping law enforcement officials to yank dangerous criminals from the state's streets to assisting police in locating missing or lost children or elderly people, said Maryland Assistant U.S. Attorney Harvey Eisenberg, coordinator of the state's Anti-Terrorism Advisory Council, which oversees the center.

In Baltimore City, which has about a dozen of the devices, they are mostly used to identify stolen vehicles, said Anthony Guglielmi, a police spokesman.

The city also wants to incorporate tag-reading technology into all its CityWatch cameras, but it hasn't begun that process, Guglielmi said.

The 44 readers operated by the Maryland State Police allow for a much more efficient force because a single officer in a patrol car can check hundreds of license plates for criminal connections per minute, in real time, said Greg Shipley, a state police spokesman.

Still, the center acknowledges "the need to balance law enforcement and national security vis-a-vis the privacy of private citizens," Eisenberg said, and has existing guidelines for data use.

Data is also kept in the center's repository for only one year, unless it is involved in an active police investigation, Eisenberg said.

Shipley said state police devices transfer data to the repository but retain information for only 24 hours.

Rocah said actions like real-time checks of tags against criminal databases likely involve "minimal privacy invasion, if any," but other actions are more questionable.

The information the ACLU has requested from 27 local police agencies, four state police agencies and seven non-police state agencies will help it assess the appropriateness of the readers' use in the state, Rocah said.

krector@baltsun.com

twitter.com/rectorsun