San Jose police, under fire for interactions with the public that have turned violent, on Friday launched a pilot project equipping officers with head-mounted cameras to record contacts with civilians.

Officers will activate the cameras, about the size of a Bluetooth device and attached by a headband above the ear, every time they respond or make contact with a person. At the end of the officer’s shift, the recording will be downloaded to a central server.

Chief Rob Davis said the devices, to be tested by 18 patrol officers, are a technological advance comparable to the advent of police cars, two-way radios and the 911 emergency system.

San Jose is the first major U.S. city to try out the devices, known as AXON.

Although officers are already bearing vests, weapons and radios, most of them welcome adding a camera to record their actions, Davis said. In addition, he said, “We’re making it so it has cachet.”

A leading critic of the department welcomed the cameras as a tool to provide useful evidence, but dismissed their significance as a solution to rocky police-community relations.

“The AXON project is unfortunately a positive thing right now because the level of distrust is so high,” said Raj Jayadev, director of the community organization Silicon Valley De-Bug. “But it doesn’t address the more fundamental problem: What stereotypes police may carry when they see people of color on the street and make assumptions about character.”

The cost of the trial is being shouldered by maker Taser International of Scottsdale, Ariz. But if the trial leads to full-fledged use, equipping the entire 1,400-officer department will be expensive. At $1,700 per kit and a $99 per officer monthly fee, the system could cost $2,888 per officer in the first year, or $4 million.

Davis said he expected the price would decrease, and he hoped that the department would be able to find grants to defray the cost.

The kit includes a camera, a control piece and a computer that can hang from the belt. In the pilot project, officers have been directed to switch on the camera as they are about to contact a civilian. The cameras, equipped with an audio recorder, align with the officer’s vision, and can be later switched to standby mode.

Afterward, the officer can switch the camera to a “buffer” mode, where it still records limited segments of video, and a nonrecord mode. The officer may review the tape at any time, but it may not be erased. At the end of the shift, the device’s memory is downloaded onto a central server.

Davis said commanders will randomly review the tapes, to evaluate the system and to gather information that could help assess police policies and procedures.

Officers, he said, welcomed the devices.

“I used it this morning in making an arrest,” said officer William Doane, one of the AXON test pilots. “It verified what I saw.” In the two days of testing, he generally remembered to turn on the AXON before incidents, but sometimes forgot to turn it off afterward, he said. Overall, he said, “It’s a good system.”

The devices could provide evidence of crimes, timely information about suspects, help with police training and be a resource in investigations of complaints against police and deterrence of public misbehavior, Davis said. Critics, however, are interested in how the cameras might prevent police from overstepping bounds.

Over several months, groups representing Latinos, Asians and African-Americans have criticized San Jose police for too easily resorting to force. Per capita, San Jose police make more arrests for resisting arrest than does any other major California city, according to a Mercury News investigation.

Criticism spiked after police fatally shot a mentally ill man, Daniel Pham, in May and after a cell phone video showed officers apparently beating Phuong Ho, a San Jose State University student from Vietnam.

A detailed review by the Mercury News showed that San Jose police have repeatedly used force in incidents that began as seemingly benign situations. In response, Davis has formed a panel to review the department’s use of force.

In 2008, police received 117 use-of-force complaints, but said none of the complaints was justified.

Jayadev said he was concerned about who would have access to AXON tapes. Given the department’s reluctance to release evidence, such as 911 tapes, he said he fears the camera tapes might prove to be a tool for police but be denied to residents facing criminal charges or criticizing police conduct.

Davis said that the department will balance privacy concerns in making the camera footage available to the public.

Jayadev also pointed out that the trial of AXON mirrors the introduction of Tasers in 2004, soon after police killed a knife-wielding woman in her kitchen.

When Davis became one of the first big city chiefs to arm all his officers with Tasers, the idea was to save lives and reduce violent contacts.

“Of course, they didn’t,” Jayadev said. “We can’t solve our problems with a new piece of gadgetry.”

Contact Sharon Noguchi at 408-271-3775.