On Aug. 3, a mobile camera spotted Minneapolis Mayor R.T. Rybak's city-owned car on 5th Avenue downtown. On Aug. 7, it found the car again on Nicollet Island. On Aug. 9, another camera saw the mayor's car on a side street near the University of Minnesota.

All of that data resides in a city of Minneapolis database containing millions of license plates scans, captured by devices mounted on city police and traffic vehicles. As a Star Tribune public records request shows, knowing someone's license plate number gives anyone access to city data about where that vehicle has been seen.

The cameras are increasingly popular with law enforcement agencies locally and nationally because they can spot criminals and other wanted persons in real time. But without a state law, the data is public and can be stored indefinitely. In Minneapolis, location data is stored for one year. St. Paul discards it after 14 days, while the State Patrol erases it in 48 hours.

Now several legislators are joining privacy experts who say the Legislature needs to set standards on the classification, retention and use of that data. "This is something that I think demands attention on a statewide basis," said Rep. Tony Cornish, R-Good Thunder, chairman of the House Public Safety Committee.

After the Star Tribune reported on the issue last week, documenting data the city had kept on a reporter, data requests began to trickle in to Minneapolis police. The department now has "License Plate Reader Request" forms, which are stored in a special binder, to document each one.

Jake Ingebrigtson, co-owner of Car and Credit Connection in South St. Paul, requested location data on four vehicles that his company is trying to repossess from people who have stopped making payments. "This can really help us try to locate vehicles," said Ingebrigtson, whose company sells cars to people with bad credit.

Tony Messner, vice president of the mechanical service company Palen Kimball, asked for location data on one of the firm's vans that was stolen and later found damaged and missing tools. "We thought maybe there is a chance that the license plate showed up in some location around town," Messner said. "And that might help us figure out what happened."

Palen Kimball may not get much back, but it's worth a shot. Over the course of a year, scanners spotted Rybak's current and former city-owned cars 41 times. The most recent captures featured pictures of the car, which are stored for 21 days. Seven of the locations were redacted because the department does not release locations of its stationary cameras.

A police spokesman, Sgt. William Palmer, said last week that they retain the data for a year "to ensure we can comply with requests for public data" and that they hope to get guidance from the state about how long to keep it. On Thursday, Rybak said he asked Police Chief Tim Dolan to develop recommendations for the City Council and him to consider.

"In some cases, the license plate data the police have retained have proven helpful in investigating and solving crimes," Rybak said in a statement. "But there are important, legitimate concerns around the length of time it is stored and how it is or can be used or accessed that we need to address."

Palmer said the department has used the database in investigations. In one instance, investigators looking for a suspect found through the scan data that his car was parked repeatedly on a block in north Minneapolis.

Minneapolis has eight mobile cameras -- split between police and traffic vehicles -- and two stationary ones that have captured 4.9 million license plates in 2012. The traffic vehicle scanners are generally used to identify parking scofflaws, city spokesman Matt Laible said. The city of St. Paul has 10 mobile cameras.

The license plate number, date and location of the vehicle are considered public data, but other information, such as the vehicle's owner and address, are not.

Last Friday, the state's Criminal and Juvenile Justice Information Task Force voted to recommend to the Legislature that the data should be classified as "private," meaning only the subject can request it from police.

"Now that we see someone's patterns in a graphic on a map in a newspaper, you realize that person really does have a right to be secure from people who might be trying to stalk them or follow them or interfere with them," said Bob Sykora, chief information officer for the Minnesota Board of Public Defense, who recommended the reclassification.

Voting no were privacy advocate Rich Neumeister and a representative of the attorney general's office, who felt the recommendation also needed to cover data retention, usage and access. "If you make things private [without addressing these issues], there's no accountability or transparency on how they're using millions of records," Neumeister said.

In a separate motion, the task force recommended the data be retained for a "limited period" and will appoint a group to determine what that should be.

Rep. Kelby Woodard, R-Belle Plaine, said he intends to introduce legislation next session that makes the license plate reader data private. "There is also a need to clearly define the legitimate uses of this data by law enforcement and a limitation to the retention of this highly sensitive data," Woodard wrote in an e-mail.

Cornish, a retired police chief, would ideally like to see the data dumped immediately if the vehicle doesn't register as wanted by law enforcement -- known as a "hit." He worries about the potential that the databases could be abused, citing past problems with state vehicle records.

"Even though technology is great and it helps catch the bad guys, I don't want the good guys being kept in a database," Cornish said.

Eric Roper • 612-673-1732 Twitter: @StribRoper