Widespread protests in the U.S. over several police shootings have refocused attention on body cameras and whether they might prevent such incidents.

A number of forces in the U.S., Canada and the U.K. already use the technology, but it’s still an open question whether it can truly change how police and the public interact.

In the face of criticism of a grand jury decision not to indict New York police officer Daniel Pantaleo for the death of Eric Garner and with the shadow of the Ferguson riots still looming, U.S. President Barack Obama pledged $75 million US for 50,000 body cameras to be distributed to police departments around the country. 

Garner died in July after a confrontation with police in which he was subdued by several officers and placed in a chokehold by PantaleoThe incident was video-recorded on a bystander's cellphone — as numerous police shootings and violent confrontations have been in recent years.

In the smartphone age, there has been no shortage of controversial police incidents caught on video, yet they continue to happen — most recently last Tuesday with the fatal police shooting of Rumain Brisbon, an unarmed black man, in Phoenix. So, will video recording the actions of police make any difference? 

Some experts think so.

Greater chance of justice

Peter Bibring of the American Civil Liberties Union has argued that the failure to indict Pantaleo is not a reason to abandon police body cameras, which are usually worn on an officer's vest, lapel or helmet or attached to glasses or headsets.

"Video evidence … provides the public with crucial information about how police operate," he wrote in a blog post on the ACLU website. "It’s in large part because of the video footage that the nation is so outraged at Garner’s killing. We know what happened — we may not have all the evidence the grand jury had, but we know a lot more than if no video existed."

'Video might not resolve every dispute, it might not guarantee indictments or discipline in every case where they're deserved — but the chances of justice without it seem much less.' — Peter Bibring, American Civil Liberties Union

The ACLU has endorsed the use of body cameras as a means of promoting police accountability, as long as departments adopt clear policies to protect privacy and limit how the recordings are used.

Video footage can help settle arguments over who did what and when and frees juries and investigators from having to rely solely on police testimony, says Bibring,

"Video might not resolve every dispute, it might not guarantee indictments or discipline in every case where they’re deserved — but the chances of justice without it seem much less," he writes.

Fewer use-of-force events, complaints

There have been several studies that seem to indicate that when police use body cameras during an encounter, it has a "civilizing" effect on all parties.

A randomized controlled trial in Rialto, Calif., which introduced body cameras for its 50 officers in 2012 after several police misconduct scandals, found that in the 12 months that body cameras were used, there was a 60 per cent drop in use-of-force incidents and an 88 per cent drop in citizen complaints about police behaviour. Studies in Phoenix and Mesa, Ariz., had similar results.

All were based on a raw comparison of numbers and provided no details of how police and citizens actually behaved during the encounters, said Michael D. White, a criminologist at Arizona State University who reviewed these trials and others for the U.S. Department of Justice.

"You know that there was this 60 per cent reduction in the use of force, but you don't really know why," he said. "Was it driven by citizens being more compliant and co-operative? Was it driven by police officers being more respectful, which then changed the tone of the encounter? We don't know."

The reduction in complaints, for example, could be the result of people being intimidated by the presence of cameras and deciding not to report an incident when under other circumstances they would have. One of the reasons police departments like body cameras is that they reduce frivolous complaints and cut down on litigation costs, but they may also dissuade legitimate complainants.

Cameras encourage by-the-book behaviour

The studies also found that officers who use body cameras make more arrests and hand out more tickets — likely out of a fear of being reprimanded by their bosses.

'It could be that the body-worn camera is having the effect of reducing officer discretion, that is, officers are less likely to resolve things informally.' — Michael D. White, criminologist

"It could be that the body-worn camera is having the effect of reducing officer discretion, that is, officers are less likely to resolve things informally because they know they're wearing the camera and they know, 'Gee, if my supervisor reviews this, and he sees that I had the potential to make an arrest and I didn't, that may come back to bite me in the butt,'" White said.

Police Chokehold Death

A protester sits in the road near Times Square while rallying against a grand jury's decision not to indict the New York police officer involved in the death of Eric Garner. (Jason DeCrow/Associated Press)

The Mesa study found that officers with body cameras conducted fewer stop-and-frisks, suggesting the presence of a camera may have led them to "think more carefully about what constitutes reasonable suspicion," according to Justin Ready and Jacob T.N. Young, the authors of the study, who described their findings in Slate.

Based on sales figures from police camera vendors like Taser and Vievu, White estimates that about 5,000 U.S. police departments are currently using body cameras, but exactly when officers turn them on varies by department, some leave it to officers' discretion, others require cameras to be on in every encounter with citizens.

This has already led to problems in some jurisdictions. Police officers in Oakland, Calif., were the subject of numerous citizen complaints after they selectively turned their body cameras on or off during the 2011 Occupy Oakland protests, and in Albuquerque, N.M., a police officer involved in a fatal shooting of a 19-year-old woman was fired for not turning on his lapel camera during the incident.

Video not always objective

Even when body cameras are on, they don't necessarily provide a foolproof, objective account of the event.

"People interpret what they see on video through their own experiences," Ready and Young, both assistant professors of criminology at Arizona State University, wrote in Slate.

"Different viewers may contextualize the event differently in terms of how it is framed in their mind, how they think it was precipitated and what they think happened in the 30 seconds before the camera started rolling."

Cameras can actually hinder some types of police work such as domestic violence calls, providing assistance to the injured or mentally ill and intervening in everyday disputes, they said.

Sammy-Yatim-Toronto-police-shooting

Smartphones have made it easier to record police confrontations. The fatal police shooting of Toronto teenager Sammy Yatim on a streetcar was caught on video by a bystander. (Facebook/Canadian Press)

"The device can be a physical reminder to crime victims that they are on camera at times when they are most vulnerable and in need of privacy," they write.

The ACLU, too, has raised concerns about the potential for invasions of privacy in certain situations such as home searches as well as about the long-term storage and use of the video police collect.

"It's vital that this technology not become a back door for any kind of systematic surveillance or tracking of the public," the ACLU said in a 2013 position paper.