License plate readers aboard police cars

How police license plate readers can invade your privacy.
by Rob Sachs

Cyrus Farivar is a journalist, radio producer and author. He is also the senior business editor at Ars Technica a Conde Nast Publication.
He has reported for The Economist, Wired, The New York Times, the CBC, PBS, NPR etc.

Cyrus Farivar, by his own admission, has an obsession. He's obsessed with a technology that most people don't even know exists: license plate readers

"I first learned about them around 2013, when I was reading a blog post" says Farivar, a senior editor with the technology news website Ars Technica. "These things were being discussed for purchase in Massachusetts by various local law enforcement agencies. I started to wonder, 'Well, OK, are these things being used in other places in America besides Massachusetts?' The answer was, 'Yes, of course.' "

License plate readers are small devices that typically sit on the roof of police cars, scanning up to 60 plates a second as the police cars drive around. "All the plates that it can see in its visual field - cars coming toward the police car, cars driving away from the police car, driving to the side, parked," Farivar says. "No matter what, it can scan them."

Then, the plate numbers are cross-referenced with a "hot list" of plates of wanted or stolen vehicles. The problem, Cyrus says, is that only a small fraction of the plates are on the wanted list. The rest of the plates are on cars that belong to non-criminal, law-abiding people - people whose movements the government could now conceivably track.

"The fear is that with enough data points, with enough instances where your car was captured, you might be revealing something about that person that the government may not already know,"Farivar says." (Not unlike the meta-data collected by cell towers hits)

This technology is used all over the country in big cities like Boston, Chicago, New York, Washington, DC, and Los Angeles, but also in some smaller cities.

As far as our friends pulled over by the Maryland Police.

But for his research on license plates readers and their effect on privacy and civil liberties, Farivar turned his attention to his own backyard: Oakland, California. He filed a records request for all the license plate reader records that had ever been collected and received 4.3 million records covering roughly four years.

He reviewed the records, identified clusters of data points on a map and - by simply matching a license plate to its owner - was able to piece together an astonishing amount of personal information like whether or not you had a handgun permit.

But still, he cautions, we need a better understanding of the limitations on government's ability to collect big data. "Just because the government has the ability to do that, in my opinion, it doesn't necessarily mean that they should be able to."