NEW YORK (AP) — What if Michael Brown’s last moments had been recorded?

The fatal police shooting of the unarmed black 18-year-old in Ferguson, Missouri, is prompting calls for more officers to wear so-called body cameras, simple, lapel-mounted gadgets that capture video footage of law enforcement’s interactions with the public. Proponents say the devices add a new level of accountability to police work.

“This is a technology that has a very real potential to serve as a check and balance on police power,” says Jay Stanley, senior policy analyst at the American Civil Liberties Union.

The case supporters make is simple: Cops and criminal suspects alike are less likely to misbehave if they know they’re being recorded. And there’s some evidence supporting it. In a recent Cambridge University study, the police department in Rialto, California — a city of about 100,000- saw an 89 per cent decline in the number of complaints against officers in a yearlong trial using the cameras.

The number of times the police used force against suspects also declined. After the trial, the cameras became mandatory for the department’s roughly 100 officers.

Rialto isn’t unique. Across the US and in England, Australia, Brazil and elsewhere, a growing number of departments are implementing the cameras, in addition to — or instead of — the dashboard-mounted cameras that are already widely used in police cars. Some one in six U.S. police departments now use body cameras in some form, according to ACLU attorney Scott Greenwood.

A recent petition submitted to the White House website calls on President Barack Obama to create a bill that would require all police officers at the state, county and local levels to wear cameras. The plea has more than 142,000 signatures.

White House officials say every petition that crosses the 100,000 signature threshold is reviewed and will receive a response. The administration could use the petition to weigh in on the broader issue of police accountability and transparency.

In the meantime, the Los Angeles Police Department is testing the cameras and the New York City Police Department said this month that the department is exploring the feasibility of using the devices. The city’s public advocate, Letitia James, has called for the cameras as a check on police misconduct following the death of a black man placed in a chokehold by a white police officer last month in Staten Island.

Cameras come with complications, however. It’s unclear whether a police body camera would have altered the situation. A bystander recorded Eric Garner shouting “I can’t breathe!” as police officer Daniel Pantaleo placed him in a chokehold. Garner later died. The city medical examiner ruled the death a homicide and the Staten Island District Attorney said this week that the case is going to a grand jury.

Although body cameras provide a record that courts and police can use to reconstruct events, there’s no guarantee the footage will provide easy answers. There are privacy concerns for all those being recorded, whether it’s the police officers, crime suspects, victims or innocent bystanders. There are also legal and procedural questions: Who gets access to the recordings? And what happens when an officer’s device mysteriously malfunctions or gets turned off at an inopportune moment?

Experts including the ACLU’s Stanley caution that with the gadgets must also come with well-thought-out policies, including guidelines that spell out how long recordings are kept and what to do in situations where footage goes missing.