When the ACLU released a report Wednesday describing widespread license plate scanning of cars on America's roadways, everyone from privacy advocates to Sunday drivers felt their basic rights of anonymity further slip away. First our data packets, and now our license plates? Isn't anything safe from the prying eyes of the government?
But when you look at how plate scanning is being used at the street level, it's easy to understand the zeal with which police have adopted it. The practice may not appeal to the defenders of civil liberties—we'll get to them soon—but the fact remains that license plates are visible to the public at large, and law enforcement say plate scanning directly benefits anyone who owns a car, and wants to keep it.
"Every day, they put out a list of every stolen car, and send that out to us on task forces," Hinch says. "We'll get a report that says, 'These stolen cars were seen in your area' with a Google map linked."
As Hinch drives around scanning plates in target areas, the scans are immediately matched against a database of known stolen vehicles. If a match is detected, a little siren goes off inside his cop car. "Any car that displays a stolen plate, we have more than enough PC [probable cause] to stop it," Hinch says.
"The car might be parked in front of somebody's house, so we can set up surveillance at the location and wait until the person returns to the car," Hinch says.
License plate scanning cameras can be mounted on the roof or the trunk of a police car, or they can be installed inconspicuously in the light bar on the roof of the car. Police also install stationary plate-scanning cameras at the sides of busy thoroughfares or at state or national border crossings.
In some cases, plate scans can be combined with other data to flesh out a sharper profile of a suspect. Hinch says images of drivers captured by police cameras at stoplights can be matched with plates to attach a face with a plate number.
Even when police have only a partial scan of a license plate, or if they have a scan showing the color or type of car its attached to, historical scan data can reveal the full plate number, and eventually the owner of the vehicle. That's exactly how police tracked down and captured a man who abducted a child in San Jose recently, Hinch says.
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