Cameras strapped to police don’t just record bad behavior by officers or people confronted in the field — they often stop the rough stuff from even beginning.

As San Francisco moves toward equipping all of its officers with body cameras, police departments big and small, from Oakland on down to Menlo Park, are reporting huge drops in use-of-force incidents as well as citizen complaints since they began using the devices.

Since deploying wearable cameras in 2010, use-of-force incidents in the 400,000-population city of Oakland have plunged 72 percent, according to department records. With 700 body cameras, Oakland has the biggest inventory in the nation.

Across the bay in Menlo Park, population 33,000, use-of-force incidents fell 33 percent after body cameras were handed out to that city’s 49 officers in 2012. Campbell has seen its citizen complaints drop by half since starting camera use in 2010 — and similar numbers are reported in Brentwood, which has been using cameras since 2008, longer than anyone in the Bay Area.

Such numbers are being watched carefully as the nation roils with protests over citizen-filmed killings of unarmed black men by police, and as an outcry builds for more accountability by officers. Adding police cameras to the myriad cell phones blinking away at confrontations seems to be helping, those on both sides of the debate agree.

'A really good thing’

“The cameras have been a really good thing for us,” said Sean Whent, the police chief in Oakland, which has endured some of the most violent protests in the nation. “I don’t think you can say they are a panacea, or are the only reason for a reduction in use-of-force incidents, but I do think they are a very good factor in that.

“It’s not just that the cops are behaving better when they know the camera is on, but people interacting with us know we’re filming, so they behave better too,” he said. “It think it has a civilizing effect on both sides of the camera.”

So far, just 15 percent of the nation’s police forces use the cameras, but the biggest maker of the devices predicts they will be nearly universal within three years.

President Obama has been urging departments to get body cameras since riots began exploding with the fatal shooting last year by a white officer of Michael Brown, an unarmed black man, in Ferguson, Mo. And this month, the U.S. Department of Justice announced a $20 million program to immediately begin equipping departments with the cameras. Obama is proposing tossing in another $55 million in camera funding over the next three years.

“It’s a no-brainer to start using these devices, with police conflict going on across the country,” said Steve Ward, chief executive officer of Vievu of Seattle, which makes 80 percent of the nation’s police body cameras. “I call this technology a win-win, because police departments want it, but at the same time the community wants the police to have it.

“I don’t know of anybody who doesn’t want them on cops,” said Ward, who was a SWAT team officer with the Seattle Police Department before founding Vievu in 2007.

He gets little argument from Chauncee Smith, racial justice advocate for the ACLU of Northern California. Smith’s main concern with the cameras is privacy rights, and openness of policy.

Privacy concerns

“The cameras do seem to have a good effect in deterring misconduct by both citizens and officers, but because it is such a new technology, we need to ensure that before they are rolled out, there is an open public process for how they will be used,” Smith said. “We have to know why they will be used, and what safeguards are in place to make sure they won’t be misused. People’s privacy needs to be protected.”

Barry Donelan, president of the Oakland Police Officers’ Association, agreed.

“We have to be very careful about how we use this footage,” he said. “These cameras often capture our interaction with citizens who are in some of the most challenging moments of their lives, being filmed at a time of trauma or when they do things they wouldn’t want their mother to see. Society has to decide — do we want all of that on YouTube?”

Already, Oakland has adjusted its camera policy to dictate that interviews with sexual assault victims not be taped, for privacy. It also doesn’t let officers review their own footage before they file a report on a use-of-force incident.

There is no statewide mandate for body camera policy, though, so the rules differ everywhere. Oakland, for instance, keeps its footage for about three years, while Brentwood stores video for a year. BART’s police are allowed to film sexual assault victims.

Setting state standards

Two bills making their way through the California Assembly would set standards on usage of body cameras and storage of footage, but no resolution is expected before the end of summer. They would represent the first comprehensive guidelines in the nation for police body cameras. Whent, the Oakland chief, has testified twice in Sacramento in support of one of the bills.

“I want to make sure everyone has these cameras, because if there is a tragedy we want to have them on to see all sides of what happened,” said Richmond police Capt. Mark Gagan, whose department began mandating use of the devices in March. “It’s not just good for us and for the citizens — it’s a teachable moment.”

Kevin Fagan is a San Francisco Chronicle staff writer. E-mail: kfagan@sfchronicle.com

Twitter: @kevinchron

When cameras roll, force declines

California cities that have outfitted police officers with body cameras are reporting drops in use-of-force incidents. These cities include:

OAKLAND

Down 72 percent in five years. Total in 2009, before cameras went

into use: 2,186. Total in 2014: 611.

RIALTO (San Bernardino County)

Down 59 percent in one year. Total in 2011, before cameras went

into use: 61. Total in 2012: 25.

MENLO PARK

Down 33 percent in two years. Total in 2011, before cameras went

into use: 9. Total in 2013: 6.