A vow by Mayor Michael Bloomberg to appeal the plan, which he has called a "nightmare," may stall the proposed yearlong pilot program in New York, where one precinct in each borough would be equipped with cameras and the results closely monitored. The goal is to provide an objective record of "stop and frisks," which U.S. District Judge Shira Scheindlin found discriminated against minorities, and to encourage more "respectful" interactions.



But already, police departments around the country are doing experimental runs with such cameras, including in cities like Phoenix and Greensboro, N.C., and smaller towns like Coeur d'Alene, Idaho. Even campus cops are getting them—at San Jose State University in California, for instance.

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There is no overall study about the effectiveness of body cameras, but there are promising signs from smaller communities.

The police department in Rialto, Calif., put cameras on a group of officers and saw the number of citizen complaints filed drop by 88 percent—and more importantly, use of force declined by 59 percent.

A test program in Fort Worth, Texas, spurred demand among officers.

"Right now, wearing the cameras is voluntary," Cpl. Tracey Knight, community liaison and PR officer for the Fort Worth Police Department, told NBC News. "However, more and more officers are requesting to have one issued to them and some have even purchased their own."

In Scottsdale, Ariz., police started using 10 body cameras earlier this summer as the agency explores outfitting up to 250 patrol officers with the cameras. Reception was cool at first, Sgt. Mark Clark says, until an incident a few weeks ago.

A police officer's camera revealed that person who filed a complaint against a motorcycle patrol officer made up the story.

"We showed the person the video and they said, 'Um, I guess I must have remembered it wrong,'" Clark told The Associated Press.

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While the cameras seem to impact police and citizen behaviors when on, exactly when they're on varies by police department. Some are automatic, others are triggered at the discretion of the officer, which can raise questions about what officers choose to record—or not.

Across Arizona, in Lake Havasu, the following video, taken by cameras worn by police officers shows how a fast-moving and volatile situation, perhaps difficult to recall in detail later, can be documented (WARNING: intense video with a man being taken down non-lethally but forcefully):