AlbSoft

Now, some police departments are using miniaturized video cameras and their microphones to capture, in full detail, officers’ interactions with civilians. The cameras are so small that they can be attached to a collar, a cap or even to the side of an officer’s sunglasses. High-capacity battery packs can last for an extended shift. And all of the videos are uploaded automatically to a central server that serves as a kind of digital evidence locker.

William A. Farrar, the police chief in Rialto, Calif., has been investigating whether officers’ use of video cameras can bring measurable benefits to relations between the police and civilians. Officers in Rialto, which has a population of about 100,000, already carry Taser weapons equipped with small video cameras that activate when the weapon is armed, and the officers have long worn digital audio recorders.

But when Mr. Farrar told his uniformed patrol officers of his plans to introduce the new, wearable video cameras, “it wasn’t the easiest sell,” he said, especially to some older officers who initially were “questioning why ‘big brother’ should see everything they do.”

He said he reminded them that civilians could use their cellphones to record interactions, “so instead of relying on somebody else’s partial picture of what occurred, why not have your own?” he asked. “In this way, you have the real one.”

Last year, Mr. Farrar used the new wearable video cameras to conduct a continuing experiment in his department, in collaboration with Barak Ariel, a visiting fellow at the Institute of Criminology at the University of Cambridge an assistant professor at Hebrew University.

Half of Rialto’s uniformed patrol officers on each week’s schedule have been randomly assigned the cameras, also made by Taser International. Whenever officers wear the cameras, they are expected to activate them when they leave the patrol car to speak with a civilian.

A convenient feature of the camera is its “pre-event video buffer,” which continuously records and holds the most recent 30 seconds of video when the camera is off. In this way, the initial activity that prompts the officer to turn on the camera is more likely to be captured automatically, too.

THE Rialto study began in February 2012 and will run until this July. The results from the first 12 months are striking. Even with only half of the 54 uniformed patrol officers wearing cameras at any given time, the department over all had an 88 percent decline in the number of complaints filed against officers, compared with the 12 months before the study, to 3 from 24.

Rialto’s police officers also used force nearly 60 percent less often — in 25 instances, compared with 61. When force was used, it was twice as likely to have been applied by the officers who weren’t wearing cameras during that shift, the study found. And, lest skeptics think that the officers with cameras are selective about which encounters they record, Mr. Farrar noted that those officers who apply force while wearing a camera have always captured the incident on video.

As small as the cameras are, they seem to be noticeable to civilians, he said. “When you look at an officer,” he said, “it kind of sticks out.” Citizens have sometimes asked officers, “Hey, are you wearing a camera?” and the officers say they are, he reported.

But what about the privacy implications? Jay Stanley, a senior policy analyst at the American Civil Liberties Union, says: “We don’t like the networks of police-run video cameras that are being set up in an increasing number of cities. We don’t think the government should be watching over the population en masse.” But requiring police officers to wear video cameras is different, he says: “When it comes to the citizenry watching the government, we like that.”

Mr. Stanley says that all parties stand to benefit — the public is protected from police misconduct, and officers are protected from bogus complaints. “There are many police officers who’ve had a cloud fall over them because of an unfounded accusation of abuse,” he said. “Now police officers won’t have to worry so much about that kind of thing.”

Mr. Farrar says officers have told him of cases when citizens arrived at a Rialto police station to file a complaint and the supervisor was able to retrieve and play on the spot the video of what had transpired. “The individuals left the station with basically no other things to say and have never come back,” he said.

The A.C.L.U. does have a few concerns about possible misuse of the recordings. Mr. Stanley says civilians shouldn’t have to worry that a video will be leaked and show up on CNN. Nor would he approve of the police storing years of videos and then using them for other purposes, like trolling for crimes with which to charge civilians. He suggests policies specifying that the videos be deleted after a certain short period.

A spokesman for Taser International said it had received orders from various police departments, including those in Pittsburgh, Salt Lake City and Hartford, as well as Fort Worth, Tex.; Chesapeake, Va.; and Modesto, Calif. In the San Francisco Bay Area, the police department of BART, the transit system, has bought 210 cameras and is training its officers in their use, part of changes undertaken after a BART police officer’s fatal shooting of an unarmed man in 2009.

Before the cameras, “there were so many situations where it was ‘he said, she said,’ and juries tend to believe police officers over accused criminals,” Mr. Stanley says. “The technology really has the potential to level the playing field in any kind of controversy or allegation of abuse.”

Mr. Farrar recently completed a master’s degree in applied criminology and police management at the Universiity of Cambridge. (It required only six weeks a year of residency in England.) And he wrote about the video-camera experiment in his thesis.

He says his goal is to equip all uniformed officers in his department with the video cameras. “Video is very transparent,” he said. “It’s the whole enchilada.”