How do the license plate scanners that law enforcement use really work?

License plate scanners take a picture of your license plate and compare it with statewide database of wanted vehicles.

To see how these license plate scanners work, CNYCentral's Dora Scheidell rode along with Onondaga County Sheriff's Deputy Robert Betchel while he looked for wanted vehicles and drivers.

The scanner is strapped Deputy Betchel's patrol car. It includes two camera mounted to the trunk which work like eyes, scanning each car as it goes by. They're linked to a computer inside his car which has access to a statewide and countywide database of wanted vehicles.

An alarm goes off when the driver or the car has a violation. The registration could be suspended or the car could be stolen, but it can also help solve more serious crimes.

"it can be used on the criminal side. It's actually saved several lives since we've had it," says Betchel.

Deputy Betchel recently stopped a kidnapping in progress. A man had his ex-girlfriend at knife point. Police had his license plate and Betchel's license plate scanner alarm went off when he drove by.

"The female was turned over to her family members unharmed and in good welfare. So the tool works out very well when it comes to something in that nature," says Betchel.

There is no law governing the use of license plate readers in New York. So the policies, such as how long the information is stored and who has access to it, is different with every agency. In Onondaga County, the information is stored in the database for up to a year and you have to be at least a sergeant to have access to it.

The American Civil Liberties Union has written a report questioning the use of these scanners because while they may help solve crimes, they also track and store the movement of people who aren't criminals.