NORTH COUNTY - The round black cameras mounted atop Escondido police Sgt. Don Shumate's patrol car are doing a lot of his work for him these days.

The cameras click rapidly, working constantly to photograph license plates on passing cars and inputting the numbers into an on-board computer, which then runs the number against a database of stolen vehicles.

If a vehicle comes back reported as stolen, the system - called automated license plate recognition - emits alerts both audibly and on the computer screen mounted beside the patrol car's steering wheel.

"It's basically a stolen car hunter," said Shumate, whose car captured hundreds of plates as he drove around Escondido one morning earlier this month. "It's looking for those I can't see. It's able to run things the human eye would miss. … They can be bumper to bumper, and we got it."

Auto theft is a continuing concern in the region, and more than 25,800 vehicles were stolen countywide last year, according to the San Diego County Regional Auto Theft Task Force. With 794 motor vehicle thefts this year through October, Escondido has the highest theft rate in North County and the fifth-highest in the county, county statistics show.

San Diego police have three license plate tracking systems, and have recovered 119 vehicles with them since last year, Detective Brian LeRibus said.

Use of the cameras has drawn some concern from civil rights activists, who said they are worried that the increased use of surveillance technology, without the use of independent oversight, could infringe on citizens' privacy.

"Our main concern is the tremendous power this gives law enforcement to track people," said Kevin Keenan, director of the San Diego and Imperial county chapters of the American Civil Liberties Union. "We all want stolen cars to be found and car thieves to be caught, but this power could be used in other ways."

In response, Shumate stressed that the devices photograph the license plate, not the driver. Furthermore, the cameras are only a tool used to speed up an officer's work, and do not provide any more information than police already have access to, he said.

The county Sheriff's Department now is working to secure funding to put two of the devices in place by next year, Lt. Phil Brust said. The California Highway Patrol is also testing the technology, though it is not in use by the agency's Oceanside office, which handles most of North County, Officer Eric Newbury said.

The system in Escondido uses three cameras mounted atop a patrol car that can capture license plates from 10 to 15 feet away in less than a second. It also scans for vehicles wanted by police or listed by an Amber alert, which is issued for missing children.

The program, developed by United Kingdom-based PIPS Technology, allows officers to check for stolen vehicles much faster than they could with the traditional method, which requires them to relay the license plate number to a dispatcher, who then checks it against the stolen vehicle database.

Shumate described that method as "very tedious."

"When you're behind a possibly stolen car, you have to manually type while driving. It typically takes 30 to 40 seconds," he said. With the reader, he said, "We can read 20 plates in that same time."

The system scans surrounding cars automatically while the patrol car is on, and officers can use other computer programs as the tracker works. If the device detects a stolen car, an alert appears over any other application the computer is doing.

Escondido employs one license plate reading system that was put into place about five months ago at a cost of $25,000, paid for with grant funds. There are no current plans to expand the program, though police will evaluate the system next year to determine whether they will buy more systems, Shumate said.

Since its employment, about 100,000 plates have been scanned, leading to 470 hits for stolen vehicles. Police are working now to track the number of vehicles recovered through the system, and it is still too early to know how successful the technology is, Lt. Bob Benton said.

The use of license plate reading technology has grown quickly in the U.S. over the last three years, and between 75 and 100 law enforcement agencies statewide currently use some type of program, said Greg Lary, vice president of West Coast Operations for PIPS Technology.

"The demand is definitely growing from a law enforcement perspective," he said.

The program is similar to that used to monitor vehicles on toll roads and to count cars for traffic management projects, Lary said. The technology, which is used extensively in the United Kingdom, was initially developed as a way to track vehicles following a 1993 bomb attack in England, he said.

- Contact staff writer Sarah Wilkins at (760) 740-3524 or swilkins@nctimes.com.