Data collected by 19 license plate readers owned by the Baltimore County police are stored securely and destroyed after a year, according to a department spokeswoman.
But the information, although wiped from county computer systems, is transfered to a state law enforcement intelligence gathering agency that the Americal Civil Liberties Union has raised concerns about.
Elise Armacost, a spokeswoman for the department answered questions about what happens to the data just a day after the American Civil Liberties Union announced it on state and local police agencies in more than 35 states.
The civil liberties group is concerned extended storage of such information could lead to privacy violations by law enforcement agencies.
"Automatic license plate readers make it possible for the police to track our location whenever we drive our cars and to store that information forever," said Catherine Crump, staff attorney with the ACLU's Speech, Privacy & Technology Project, in a statement 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."
Armacost said the devices are used for limited police activities.
"We use them as a law enforcement tool to help locate suspects, people with outstanding warrants, stolen vehicles and missing children or other missing persons," Armacost said in an email response to questions.
"We follow International Chiefs of Police guidelines that say readers will not be used to collect information at places of worship, political rallies or events, or medical facilities," Armacost wrote, adding that there is no link between the license plate readers and red light or speed cameras.
"Some people mistakenly assume that these tag readers are connected to red light or speed cameras; they are not linked in any way, nor are they used for intelligence gathering," she wrote.
Six of the county's license plate readers are assigned to the Regional Auto Theft Task Force. The remaining 13 are assigned to the county's 10 precincts.
The data is kept in a secure system and removed from county computer systems after a year. The information, however, is sent to the Maryland Coordination and Analysis Center, Armacost said.
There are more than 320 such devices in use in Maryland. More than 43 percent of those are connected to the Maryland Coordination and Analysis Center which used to be tasked with tracking just terrorist activities but now has an expanded role in all crimes, according to the ACLU.