MELISSA BLOCK, HOST:
There's another surveillance device that's become the new normal for law enforcement, and that's license plate readers.
AUDIE CORNISH, HOST:
You may have seen one mounted on police car as you've driven by. But if you haven't seen them, don't worry. Chances are, especially if you live in a big city, a license plate reader has seen you.
BLOCK: They do exactly what the name says - read your license plate and keep tabs on where your car has been and when.
CORNISH: If this makes you uncomfortable, you're not alone. Louisiana Governor Bobby Jindal last week vetoed a bill that would allow police to use them. He cited privacy concerns.
BLOCK: It may or may not be a privacy issue. We are talking about cars being used on public roads.
CORNISH: Still, to some, the thought of police collecting your license plate information is unnerving.
BLOCK: Cyrus Farivar is a senior business editor for Ars Technica. That's a technology news website.
CYRUS FARIVAR: I think where it gets creepy is not the act of scanning in and of itself. Where it gets creepy, to my mind, is that the data is kept for long periods of time and where extensive analysis can be run on this kind of data.
CORNISH: Farivar lives in Oakland, Calif., where license plate readers have been used by police since 2006. For a recent story, he was able to get all of the data collected over a nearly four-year period by the Oakland PD.
BLOCK: Added all up, that's more than 4.6 million reads of more than a million unique license plates. And Farivar showed what he could do with this data to an Oakland City Council member.
FARIVAR: Knowing nothing else about him, and just when I asked him for his license plate number and I punched it into our database, then I looked at the map and I said, you know, I bet you live on this particular block. And he said, yes, I do.
CORNISH: Farivar says this data can also be used to find out who in Oakland goes to a certain church or a medical marijuana dispensary.
FARIVAR: Once you know those plates, you know which cars to look for if you wanted to target Muslims or pot smokers or Christians or, you know, anyone else that is engaged in legal and constitutionally protected behavior. It would be really easy to establish sort of a pattern of behavior.
BLOCK: Complicating things is that there are no uniform rules governing how long this data is kept and how accessible it is to the public. Farivar says that for the police, most of this information is useless. Limiting how long the data can be kept, he says, is the first step to preventing its abuse. Transcript provided by NPR, Copyright NPR.