The claim
“The police put millions of innocent people under surveillance in order to catch a tiny minority of wrongdoers. Perhaps now it is time to make officers wear a camera and microphone while on duty.

“When they tried this in California, use of force by police officers dropped by two-thirds in a year.”

David Davis, Conservative MP, in the Times, 23 October 2013

The ongoing plebgate affair hinges on whether MP Andrew Mitchell swore at the police and called them “plebs” or not. It’s one person’s word against another.

If it had been filmed, says Mr Davis, none of this would be happening. That’s why he’s advocating that all police officers in the UK should be fitted with cameras recording everything they say and do. London Mayor Boris Johnson has backed his suggestion too.

Does putting cameras on cops improve police behaviour?

The background

Mr Davis cites the key piece of evidence in this area: a study carried out by Cambridge University researchers in a small city in California – Rialto.

If Mr Davis and the Mayor of London get their way, this year-long trial on a police force of 157 could be the basis for changing policing across the United Kingdom and installing cameras on cops across the country.

A judge in New York has already asked for the police in certain boroughs of the city to wear cameras – also based on the evidence from this study. A suggestion that would affect a million people in the city.

The study that has got law-makers on both sides of the Atlantic pushing for a major change in policing is a 14 page piece called ‘Self-awareness to being watched and socially-desirable behavior: A field experiment on the effect of body-worn cameras on police use-of-force‘

The headline results of the study are striking. After putting small wearable cameras on police officers in the Californian town of Rialto, complaints against the police fell by 88 per cent after one year of the trial.

And police officers used force on 59 per cent fewer occasions than the year before the cameras came in. It was also noted that the camera-carrying cops were less likely to use force than the control group of Rialto cops who weren’t carrying cameras.

So do cameras actually improve police behaviour or the behaviour of the public?

The analysis

People behave better when they know they’re being watched, says Dr Barak Ariel, author of this cop camera study and a visiting researcher at the Department of Criminology at Cambridge.

That’s the principle behind the whole Rialto experiment. The study explains it this way: “A voluminous body of research across various disciplines has shown that when humans become self-conscious about being watched, they often alter their conduct. Accumulated evidence further suggests that individuals who are aware that they being-observed often embrace submissive or commonly-accepted behaviour…”

In the trial, police wore small cameras mounted on collars, earpieces, and even Oakley sunglasses.

The results at the end do show significant reductions in complaints against the police and occasions when the police used force.

But the catch is that the numbers are small.

Yes police complaints dropped by 88 per cent, but it’s only a fall of 21 complaints: down from 24 complaints in 2012 to three the year after the cameras were introduced. Three is a very small number, but to take a comparison point – complaints fell by 23 between 2011 and 2010 – from 51 to 28.

The stats on the use of police force also show a dramatic drop but again, the numbers are small.

Police in Rialto used force some 61 times in the year to February 2012. The year after on-cop cameras were introduced the number of incidents fell to 25, a drop of 59 percent – the two thirds that Mr Davis refers to.

But though the statistics are small, they are significant, says Professor Lawrence Sherman, Director of the Jerry Lee Centre of Experimental Criminology in Cambridge. He helped design the study that was written up by his colleague Dr Ariel.

“The numbers are very adequate for answering the question. The question was in Rialto, what difference would wearing cameras make to police complaints and the use of force? When the sample size shows a huge effect, it shows you that it has adequate power.”

Professor Sherman compared the change to other technical developments that have revolutionised whole fields – hygiene for example.

“The handwashing experiment in Vienna, when doctors started to wash their hands, the death rate of women who had just given birth fell from 15 per cent down to two per cent. It’s been clear to everybody ever since that if you look at the data, that it made a huge difference in preventing the spread of infection.”

Is it transferable? The UK College of Police are actively conducting research into cop cameras – telling us on Wednesday that they are looking for police forces where it can be tested.

The Hampshire police force is already ahead of the curve – they’ve been testing wearable cameras or Body Worn Video for police officers since 2008. In April 2013, they decided to roll it out further – a trial that is on-going.

The verdict

It’s a striking case study analysed in depth, with very clear results. But Professor Sherman, one of the leading brains behind it, acknowledges that it needs more rigorous testing, to get stronger evidence.

“I will strongly recommend that they use randomised trials in any tests that they do in the UK, but I can’t guarantee it because frankly there’s a real reluctance to use randomised trials by people in power,” he said.

“We’ve done randomised tests with mid-level police who want to be scientific, but when an issue becomes this powerful you get people who are impatient… Rialto is by far the best evidence available, because it was done properly.”

And there’s another question. Will it actually be the police that the cameras will be turned on? The answer in Hampshire at least is no.

“It will make officers more professional, but that’s a side-effect,” said Inspector Steve Goodier, who is leading on the Body Worn Video project for Hampshire, a project he hopes will be “a template” for other forces in the country.

The camera, as far as Hampshire are concerned, is used to gather evidence against criminals that can be used to support prosecutions: “The camera is an independent witness. When you have your camera running it’s undeniable that that is what went on between the officer and the subject. It captures evidence firsthand that is used in a number of ways to support the prosecution case.”

He can cite several cases where it was used to prosecute criminals, but none he knows of where the footage was used to investigate a police officer.

Professor Sherman maintains that the cameras will need to be on all the time a police officer is on duty – bar bathroom breaks – in order for the system to be worthy of trust and for police to be fully transparent.

But in the implementation in Hampshire, that is not what is being done, said Inspector Goodier.

“It’s only turned on when the officer deems it necessary to turn it on. It’s not indiscriminate recording, it’s incident specific. The officer has to decide – should I turn the camera on. But in general we’re saying to officers – if you’re going to invoke a power in law, you should be turning your camera on. If you want to stop a person or a vehicle.”

Filming doesn’t automatically restore trust in the police. Nor does it automatically make officers or members of the public behave.

“It is just a tool,” as the Police College press officer told us – so how it is used and the framework around it will make a big difference to what impact these miniature cameras have.

By Anna Leach