The deaths of Michael Brown and Eric Garner might never have happened if police had been wearing cameras. That's one lesson from a recently published study on the effect that body-mounted cameras have on police officers' use of force.

This isn't just about police conduct. The general public, as well as police, act differently when they know that they're being filmed, and the result is a lot less violence. When cameras were worn, use of force by officers dropped by more than half, and complaints against them fell nearly ten-fold in the study.

For 12 months all police officers in Rialto, California were randomly assigned to either work shifts where they wore high definition cameras that recorded all contacts with the public or to shifts in which they worked without the cameras.

Despite the promising findings, the authors caution that there's a lot more that needs to be figured out before body-worn cameras become standard police equipment.

The results of nearly 50,000 hours of police-public interactions showed that when officers wore the cameras, use of force dropped by 59% and complaints against the police fell by 87%, when compared to the previous year's figures.

Complaints dropped from 0.7 per 1,000 contacts with the public to 0.07.

Knowing that you are being filmed creates a self-awareness in everyone, officers and civilians alike, the researchers say. This prevents situations from escalating before they get out of hand.

Being filmed alone is not enough. Eric Garner's death was digitally recorded by bystanders, but neither Garner nor the police knew that they were being filmed.

The huge drop in incidents involving force and in complaints against police during the 12 months led the Rialto police department to approve a three-year plan for officers to continue wearing the cameras. The Rialto experiment is currently being replicated in over 30 locations worldwide, from Northern Ireland to Uruguay.

Despite the promising findings, the study authors caution that there's a lot more that needs to be figured out before body-worn cameras become standard police equipment. Questions ranging from exactly how video evidence will affect criminal trials to how the vast amount of data will be stored and handled to how to stop embarrassing personal footage from ending up on the six o'clock news are some of the issues that need to be settled.

Then there's the matter of cost. The study did find that Rialto saved approximately $4 in litigation costs for every dollar spent on the program. But, according to Rialto's police chief, startup costs for Rialto's 54-officer police staff were about $150,000. The cameras themselves run about $1,000, and there are many other costs, including batteries and software. A cash-strapped town might have trouble coming up with that amount of money, while larger cities will need much, much more, just to get started.

Still, as the deaths and civil unrest from 2014's policing point out all too well, it's hard to put a price on peace and harmony. And this study suggests that's what these cameras may offer.

The study appears in the Journal of Quantitative Criminology.