Police body cameras have become a rallying cry in the wake of racially charged decisions by grand juries in Ferguson, Missouri, and New York City, but experts caution that increased use of the devices may raise more questions than answers.

Often what is filmed may appear excessive to a person unfamiliar with police work, even though the conduct may be legal.

"There's this saying in policing: 'It's lawful, but awful.' It's technically legal to do that, but it's a terrible thing to do ... We have to work on the awful piece, that's what we need to focus on," said Jim Bueermann, who heads the nonprofit Police Foundation.

Officers in one of every six departments around the country now patrol with tiny cameras on their chests, lapels or sunglasses. And President Barack Obama wants to spend $74 million to equip another 50,000 with them around the country.

A camera captured a white New York police officer applying a chokehold that led to the death of Eric Garner, an unarmed black man. In Ferguson, Missouri, there was no camera showing what happened when a white police officer fatally shot Michael Brown, a black man.

In both cases, grand juries declined to indict the officers.

Many law enforcement officials support cameras' use and say they are effective.

The police department in Rialto, California, found after a yearlong University of Cambridge study last year that the cameras led to an 89 percent drop in complaints against officers, possibly reining in misbehavior on the part of the public and officers as well as ultimately limiting department liability.

"If it were up to me, every officer walking around in a uniform would be wearing a body camera," said Martin J. Mayer, a California-based attorney who has defended law enforcement agencies for more than 40 years.

Most civil libertarians support their expansion despite concerns about the development of policies governing their use and their impact on privacy. Rank-and-file officers worry about being constantly under watch, or that an errant comment may be used by a supervisor to derail their careers.

Officers, however, generally have the law on their side.

A 1989 U.S. Supreme Court case concluded that claims an officer used excessive force must be judged by whether the officer's actions were " 'objectively reasonable' in light of the facts and circumstances confronting them" at the time.

With video evidence, "we're being forced to confront exactly what these legal standards mean," said Peter Bibring, a staff attorney for the ACLU of Southern California. "It provides the public a much better foundation to draw their own conclusions about what police are actually doing, and whether they believe it's appropriate."

Mayer said that in most states the penal code allows officers to use "the amount of force necessary to repel and overcome" force used by an individual. "It's not just to match. It's to overcome it," he said.

Camera footage provides an independent record from the officer's perspective and tangible evidence that cannot be changed, unlike often malleable and faulty eyewitness accounts, experts say. But video is limited, only showing what's in front of it after the camera is turned on.

That allows for interpretation and ambiguity that can inflame the public, regardless of what the law allows.

"At the end of the day, if people don't like the lack of an indictment, then they have to look at what the legal standard is in these cases. Sometimes that's the law," Bueermann said.

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Tami Abdollah can be reached at http://www.twitter.com/latams.