Just after midnight on Oct. 26, the stolen Jeep Cherokee of a university professor who was slain the previous morning passed a camera mounted on a pole. It took the automatic camera less than a second to scan and process the license plate number, discover it in a database and send out an alert to police cruisers.
A detective spotted the vehicle and gave chase, leading to the arrest near downtown Washington of the 18-year-old driver, who is being held in nearby Montgomery County, Md., on auto theft charges and is considered "a person of interest" in the homicide, police said.
The technology used in this case has recently swept the country. Long used in Europe, it is now employed in all 50 states and is also helping to combat the flow of drugs, illegal currency and weapons across the U.S.- Mexico border.
U.S. Customs and Border Protection awarded a contract in October worth as much as $350 million to increase its use along the border, where thousands of license plates are processed by the system every day.
But the technique, which, unlike speed cameras, snaps pictures of all vehicles passing by, worries privacy advocates. Wary of its ability to pinpoint and store the location of vehicles, they worry that innocent people may become easy targets for tracking.
Read More: License plate readers help police and Border Patrol, but worry privacy advocates
