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Questions Remain About How To Use Data From License Plate Scanners

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License plate scanners have helped police locate stolen vehicles and have even assisted in murder investigations. But with their ability to track a person's every move, skeptics worry about privacy.

License plate scanners have become a fact of life. They're attached to traffic lights, on police cars — even "repo" staff use them. All those devices have created a torrent of data, raising new concerns about how it's being stored and analyzed.

Bryce Newell's laptop is filled with the comings and goings of Seattle residents. The data comes from the city's license plate scanner, acquired from the police through public disclosure requests. He plugs in a license plate number, uncovering evidence of long-forgotten errands.

"Looks like we have you here on University Way," he says. "And this was at 3:30 in the afternoon," he says.

Newell is a PhD student at the University of Washington. He studies surveillance and is experimenting with what people can find out from stored license plate data. The scanners have already proven themselves when it comes to finding stolen cars, but Newell says with a big enough data base of this information, people could do so much more.

"As we mix data between roving systems on these patrol cars and systems mounted on, say red lights, law enforcement could get a much better picture of our individual movements," he says. "And with enough data, [police can] predict when we might leave our home and when we might be at home, for instance."

It's hardly an invasion of privacy for someone to scan a license plate. After all, that plate was meant to be public. But with millions of scans, patterns emerge. That means unusual activity stands out. And some police agencies have started experimenting with this kind of analysis.

Ron Sloan is director of the Colorado Bureau of Investigation. They've tried analyzing licence plate scans from an area near where a murder victim was found.

"We were able to do some rudimentary analysis of that data to try to determine whether or not there were vehicles that were going through the area that did not live in the area, that were from outside of the area or vehicles that that would not have been their route driving home," he says.

Sloan says it's a promising technique, but it's one he fears police will lose because of privacy fears. He and several other heads of police associations recently sent Congress a letter warning that public "misconceptions" may end up restricting police use of license plate data. Sloan says people should remember that the police are not the NSA.

"I think it's helpful for people to understand that their fears that they're being tracked or that they are somehow having their privacy violated by tracking their personal pursuits over time is not even something we have the capabilities of doing. And we have no interest in that."

But states keep passing new restrictions on how long police may store license plate data. Under these laws, police have only a few months before they have to hit delete. Still in the long run, these state laws may be moot because even as states limit the size of police databases, private ones keep growing.

Jennifer Lynch is an attorney with the Electronic Frontier Foundation. She says the nation's biggest collections of license plate data are in private hands, controlled by companies such as "Vigilant Solutions." And their information is basically unregulated.

"Private companies don't have the same responsibilities as government," she says. "Vigilant doesn't have to provide any transparency to the public about how it collects the data, how long it retains it for and who it shares it with."

These companies have been amassing license plate data from their clients — police departments around the country — as well as private contractors and other sources. That means the richest databases are held by the private sector, not the government.

But that doesn't mean the government can't use them. The Department of Homeland Security recently announced plans to use a commercial service for nationwide license plate searches. The plan is meant to answer privacy fears, since the database won't be in government hands. But that doesn't reassure Lynch.

"The fact that a private company is collecting the information doesn't really make me feel any more secure in my privacy and civil liberties if law enforcement agencies and the federal government can access it in any case."

Homeland Security wouldn't give NPR an interview about its plan to use commercial databases, but in a memorandum, it recognized "potential privacy risks" and it pledges to "follow the DHS Fair Information Practice Principles to the extent possible."

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