Police in Minnesota and across the country are increasingly using small car-mounted cameras to scan thousands of license plates and pinpoint -- in real time -- stolen vehicles, suspended drivers and criminals.

Those same cameras also record the time, date and location of every car they see and store the information. That disturbs privacy advocates, who want more details about the cameras and are calling for standards to govern how police classify and retain plate-reader data.

Without a state law, departments in Minnesota are free to set their own policies on how long they keep the information. The State Patrol deletes location data after 48 hours, St. Paul police erase it in 14 days and Minneapolis retains it for a year.

Minneapolis cops captured data on 805,000 license plates in June alone, and 4.9 million so far this year. When a Star Tribune reporter requested data on his own license plate under Minnesota's open records law, the Minneapolis Police Department responded with a list of dates, times and coordinates of his car that illustrated his daily routine.

Over the course of a year, cameras in squad cars logged him heading to work on W. Franklin Avenue at 8:07 a.m. one day, returning home on Portland Avenue S. at 6:17 p.m. on another, and parking three times late at night outside a friend's house in Uptown. Police had captured the car's license plate seven times.

"The technology that would make '1984' possible in real life exists now," said Chuck Samuelson, executive director of the Minnesota ACLU, which recently joined 35 of its affiliates nationwide to file data requests on how local agencies use the technology. "But the infrastructure to protect individuals' privacies and rights doesn't exist, particularly on the legislative and the judicial side."

"The Minneapolis Police Department has no guidance from the state of Minnesota as to how long this data should be kept," Sgt. William Palmer said in a statement Friday. "We are hopeful that such guidelines will be put in place for a statewide standard. Until such a time as guidelines are established the MPD has decided to keep this data for a period of one year to ensure we can comply with requests for public data."

Public information

So who has access to your location data? Anyone who asks for it, according to Bob Sykora, chief information officer for the Minnesota Board of Public Defense. Sykora warned in a memo this June that location data retained by police is currently public. That means it could be obtained via record requests by data miners or other members of the public, he wrote, enabling burglars to learn someone's daily routine or ex-spouses to track former partners.

"I really believe there's a potential for somebody getting hurt or killed," said Sykora, a member of the Criminal and Juvenile Justice Information Task Force, who will tell that body Friday that the Legislature should classify the data as private so only the subject of the data could obtain it.

Currently, only the plate number, time, date and location are available to the public, Sykora said. Other substantive information, such as the vehicle owner's name and address, are already private. So a person would need to know the license plate number to track someone else's car.

Rich Neumeister, a privacy and open government advocate, has been making extensive requests of local law enforcement agencies to determine how each uses license plate readers. "The bottom line in all this is that law-abiding citizens' privacy and due process are compromised here with the new technology," Neumeister said.

He would like the Legislature to address how long the data can be retained, how it can be shared and when police can use it. "Standardization is important for our liberty and privacies," said Neumeister, who has found that agencies have implemented wildly different policies -- in some cases no policy at all -- largely out of public view.

The growing use of the technology has spurred a few other states to create laws governing their use. Maine passed a law in 2010, for example, that makes plate-reader data confidential and requires it to be erased in 21 days unless it is part of an investigation.

Widespread use

Use of license plate readers has expanded dramatically in recent years. Agencies using them in the metro area include Minneapolis, St. Paul, Bloomington, Lakeville, Maplewood, Washington County and the State Patrol. In March, the state Department of Commerce issued grants for even more departments to purchase readers, including four for the Hennepin County Sheriff's Office.

"The [license plate reader] is valuable technology that saves time for the trooper while allowing them to be more productive and less distracted while observing license plates," said Lt. Eric Roeske of the State Patrol in a statement.

St. Paul has used the cameras since 2008 and now has 10, all of which are mobile, said police spokesman Howie Padilla. He said they do not share the data with other departments.

Minneapolis uses mobile readers on squad cars, traffic enforcement vehicles and cameras installed on bridges. Palmer said there are eight vehicle cameras and at least two stationary cameras. One stationary camera captured the Star Tribune reporter, but police redacted its location.

In Minneapolis, the cameras capture 13,000 to 36,000 plates a day, according to documents the Star Tribune obtained. About 6,100 of the 805,000 reads in June were "hits," meaning they matched a state database of about 400,000 listings, including stolen vehicles, revoked licenses, wanted criminals and missing persons, among other categories.