The American Civil Liberties Union says police are violating drivers' rights with license plate scanners that can be used to track their whereabouts with little oversight on how such data is used or stored.
The ACLU on Wednesday announced the results of a nationwide survey on how law enforcement agencies use license plate scanners on cruisers, road signs and bridges, and what they do with the data they collect.
Police in Maryland and across the nation run tag numbers to identify stolen or suspect vehicles, but the ACLU said the data collection goes further than many realize.
In Maryland, the ACLU said, only 47 of every 1 million plates read — or .005 percent — were linked to a stolen car or serious crime. But many departments held on to the information or forwarded the data to a state analysis center anyway, the ACLU said.
There are at least 371 state-funded scanners in Maryland across 60 state and local police departments, and the number is growing as technology cheapens, giving law enforcement agencies more information to sift, sort and store.
"There's more and more data fed in, and as it's stored for more and more time, it presents an ever richer portrait of innocent Marylanders' movements around the state." said David Rocah, senior staff attorney for the ACLU of Maryland.
The ACLU said it used public records laws to obtain 26,000 pages of documents from federal, state and local agencies in 38 states and Washington.
The report comes amid increased discussion of government surveillance, following revelations about massive telephone and email data collection programs by the National Security Agency.
Lawmakers at a congressional hearing Wednesday said they did not intend to authorize collection on the scale revealed by former NSA contractor Edward Snowden.
The ACLU report raised similar concerns. An official with AAA Mid-Atlantic said the group supports the use of license plate readers by police to track stolen cars and fugitives and keep roadways safe.
"We do, however, have concerns regarding law enforcement agencies using the technology to build historical databases that can track the movement of vehicles, as we view this as an invasion of privacy," said Ragina C. Averella, a AAA public and government affairs manager.
According to the Governor's Office of Homeland Security, 72 license plate readers were fixed on "critical" roads, bridges and other structures in Maryland in 2012.
The data captured by those cameras, as well as hundreds of mobile units in police vehicles, provided agencies with real-time information on wanted or missing persons, stolen cars and other criminal or "terrorist-related intelligence," officials said.
More than 70 percent of license plate readers in the state feed into the Maryland Coordination and Analysis Center — the state's intelligence "fusion center," where information is used for criminal and counterterrorism investigations.
The database collected more than 85 million license plate images last year.
The ACLU doesn't object to the use of the license plate readers to flag stolen cars or find fugitives, said staff attorney Catherine Crump, the report's lead author. But the organization is concerned that there aren't any uniform standards on how the information is stored, collected, used and protected, she said.
Harvey E. Eisenberg, the coordinator of the Anti-Terrorism Advisory Council of Maryland, said the state's fusion center has rigid policies and board oversight that govern its data.
Eisenberg, an assistant U.S. attorney, said the information sits in a database for one year and can be accessed only by law enforcement agencies that can prove they need it for specific criminal investigations.
"If it hasn't been requested by a law enforcement investigation," Eisenberg said, "it will sit."
But the way that law enforcement agencies use the license plate readers varies from jurisdiction to jurisdiction.