Arizona public safety officer David Callister was driving near a 1991 Nissan sedan when an alert sounded inside his cruiser and an image of a license plate flashed on his laptop. It was a signal that the car was stolen, reports the Associated Press. The alert came from a $20,000 device that uses infrared cameras mounted on the police car to scan license plates and match the numbers against databases of stolen vehicles and people wanted for crimes. Callister wasn’t focusing on the old car. “The plate reader would get you stuff you wouldn’t normally be thinking about,” he says.
About 400 of the nation’s 18,000 police agencies own at least one license plate scanner. They are expected to become more common as the price of the devices falls. The readers let officers scan about 75 times more plates during an eight-hour shift than the traditional method: writing down numbers and running them past a dispatcher. Civil libertarians say the scanners raise the troubling question about whether the government will expand its use of the technology to track people’s private lives. Police say anyone can jot down license plate numbers on a street corner; the scanners do that, only more efficiently. Patrick Camden, a spokesman for the Chicago Police Department, said, “You’re driving on a public way. There is no privacy about driving a car on a public way.”