Police can also plug any license plate number into the database and, as long as it passed a camera, determine where that vehicle has been and when. Detectives also can enter a be-on-the-lookout into the database, and the moment that license plate passes a detector, they get an alert.
It’s that precision and the growing ubiquity of the technology that has libertarians worried. In Northern Virginia recently, a man reported his wife missing, prompting police to enter her plate number into the system.
They got a hit at an apartment complex, and when they got there, officers spotted her car and a note on her windshield that said, in essence, “Don’t tow, I’m visiting apartment 3C.” Officers knocked on the door of that apartment, and she came out of the bedroom. They advised her to call her husband.
A new tool in the arsenal
Even though they are relatively new, the tag readers, which cost about $20,000 each, are now as widely used as other high-tech tools police employ to prevent and solve crimes, including surveillance cameras, gunshot recognition sensors and mobile fingerprint scanners.
License plate readers can capture numbers across four lanes of traffic on cars zooming up to 150 mph.
“The new technology makes our job a lot easier and the bad guys’ job a lot harder,” said D.C. Police Chief Cathy Lanier.
The technology first was used by the postal service to sort letters. Units consist of two cameras — one that snaps digital photographs and another that uses an optical infrared sensor to decipher the numbers and letters. The camera captures a color image of the vehicle while the sensor “reads” the license plate and transfers the data to a computer.
When stored over time, the collected data can be used instantaneously or can help with complex analysis, such as whether a car appears to have been followed by another car or if cars are traveling in a convoy.
Police also have begun using them as a tool to prevent crime. By positioning them in nightclub parking lots, for example, police can collect information about who is there. If members of rival gangs appear at a club, police can send patrol cars there to squelch any flare-ups before they turn violent. After a crime, police can gather a list of potential witnesses in seconds.
“It’s such a valuable tool, it’s hard not to jump on it and explore all the things it can do for law enforcement,” said Kevin Davis, assistant chief of police in Prince George’s County.
The readers have been used across the country for several years, but the program is far more sophisticated in the Washington region. The District has 73 readers; 38 of them sit stationary and the rest are attached to police cars. D.C. officials say every police car will have one some day.