San Jose police are testing head-mounted cameras to record interactions with the public.
The test using 18 patrol officers comes as citizens' groups criticize the department for too often using force during arrests.
Officers are to turn on the cameras every time they talk with anyone. They download the recordings after every shift, the San Jose Mercury News reported.
The cameras are the size of a Bluetooth cell phone earpieces and attach by a headband above the ear.
San Jose is the first major American city to try the devices, made by Taser International. Taser is paying for the experiment, but the price could be high if San Jose equips all 1,400 officers.
Each kit costs $1,700, plus a $99 per officer monthly fee. That's $4 million department-wide each year.