The occupant was said to be violent, so officer Carlos Ramirez approached the apartment warily. A dank smell wafted from inside. Ramirez bristled with body armour, radio, gun and Taser, but before knocking on the door he adjusted just one piece of equipment: a tiny camera on his collar.
A tubby, barefoot man with broken teeth and wild eyes opened the door. He appeared to be high. Ramirez questioned him about allegedly beating and evicting his stepson, a mentally disabled teenager. The man shifted from foot to foot and babbled about death threats.
The encounter, tense but polite, ended inconclusively, a routine police foray into family dysfunction – except for the fact it was all recorded. As he returned to his patrol car and next assignment, Ramirez tapped an app on his phone and uploaded the video. "Somewhere down the line something could happen and what that guy said, his demeanour, could be evidence."
Rialto, a small, working-class city that bakes in the San Bernardino foothills outside Los Angeles, appeared in the films Transformers and The Hangover. Among law enforcers, however, it is becoming better known for pioneering the use of body cameras on police officers.
Over the past year all 70 of its uniformed officers have been kitted out with the oblong devices, about the size of stubby cigars, and the results have emboldened police forces elsewhere in the US and in the UK to follow suit.
The College of Policing recently announced plans for large-scale trials of body-worn video in England and Wales, saying Rialto's experiment showed big drops in the use of force and in public complaints against officers. David Davis, a former shadow home secretary, has backed the idea. It follows "plebgate's denting of public trust.
Rialto has also become an example for US forces since a federal judge in New York praised its initiative.
"I think we've opened some eyes in the law enforcement world. We've shown the potential," said Tony Farrar, Rialto's police chief. "It's catching on."
Body-worn cameras are not new. Devon and Cornwall police launched a pilot scheme in 2006 and forces in Strathclyde, Hampshire and the Isle of Wight, among others, have also experimented.
But Rialto's randomised controlled study has seized attention because it offers scientific – and encouraging – findings: after cameras were introduced in February 2012, public complaints against officers plunged 88% compared with the previous 12 months. Officers' use of force fell by 60%.
"When you know you're being watched you behave a little better. That's just human nature," said Farrar. "As an officer you act a bit more professional, follow the rules a bit better."
Video clips provided by the department showed dramatic chases on foot – you can hear the officer panting – and by car that ended with arrests, and without injury. Complaints often stemmed not from operational issues but "officers' mouths", said the chief. "With a camera they are more conscious of how they speak and how they treat people."
The same applied to the public; once informed they were being filmed, even drunk or agitated people tended to become more polite, Farrar said. Those who lodged frivolous or bogus complaints about officers tended to retract them when shown video of the incidents. "It's like, 'Oh, I hadn't seen it that way.'"
Cameras made officers more careful about using force. "It's still part of the business, they still do it. But now they make better use of what we call verbal judo."
Fewer complaints and calmer policing, said Farrar, would reduce lawsuits and expensive payouts.
Images of police brutality have shaken California since grainy footage of Los Angeles police officers beating Rodney King ignited riots in 1992. (Rialto police fished King out of his pool after he accidentally drowned last year).
In May sheriff's deputies in Kern county confiscated videophone footage of them fatally beating a father-of-four, David Silva, prompting suspicion of a cover-up.
Videotaped sheriff's beating prompts charges of coverup after death - Los Angeles Times In those and other cases the officers did not know they were being filmed.
Farrar is a wonkish contrast to the stereotypical abrasive commander of TV dramas. He has several degrees, including a recent master's from Cambridge's Institute of Criminology, which planted the idea of methodically assessing the impact of body cameras.
Upon returning to Rialto (city motto: "bridge to progress") he obtained $100,000 (£62,640) in state and federal funding for the Taser-made cameras – about $1,000 each – plus servers and fibre-optic cables. Each officer has his or her own camera, mounted on collars, spectacles or caps, and is expected to activate it during interactions with the public. Encounters are logged and uploaded to a secure digital cloud service, evidence.com.
The chief advised bigger departments who wish to do the same to scale up incrementally, to iron out technical bugs and let officers get used to the idea.
In Rialto some bristled at the intrusion, fearing loss of privacy and autonomy. "I heard guys complaining it would get them into trouble, but I've had no problems so I'm OK with it," said Ramirez.
Most now accepted cameras as another part of the job, said Sgt Josh Lindsay. A self-confessed technophile, he said they provided context to contentious incidents partially captured by bystanders' phones. "Now you can see the [suspect] punching the officer twice in the face before he hits him with his baton."
Even more valuable, cameras aided evidence gathering, such as statements from domestic abuse victims, he said. "By the time those cases get to court often things have cooled down and the victim retracts. But with the video you see her with the bloody lip. There's nothing lost in translation."
Under California law police are not obliged to inform people of the filming. Local media coverage has spread awareness of the cameras but many, like the barefoot man questioned by Ramirez, appear oblivious. If there is to be a backlash, it is too early.
Even Orwell did not anticipate body cameras in 1984, but the American Civil Liberties Union of Southern California, a frequent critic of police abuses, said with the right controls accountability gains would outweigh privacy concerns. It urged the department to regularly delete videos, and keep them private, unless needed for prosecutions.
Farrar said controls were in place. "No one wants to see these videos on YouTube."
