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John Locher, Associated Press
Las Vegas police officer Nicole Hemsey demonstrates a body camera, seen on her shoulder, Wednesday, Nov. 12, 2014, in Las Vegas. The camera is the same type now being used by about 200 street officers in Las Vegas.

LAS VEGAS — Las Vegas police and a UNLV researcher say they're studying the effect that lapel video cameras have on officers and the public.

Almost 200 patrol officers are wearing cameras every day, and Lt. Dan Zehnder said Wednesday that video has been used 11 times since March to clear officers when someone wanted to complain.

Zehnder referred to the controversial police shooting of a teenager in Ferguson, Missouri, and says a lot of questions would have been answered if the officer who shot him had been wearing a camera.

The program in Las Vegas is being funded by a $107,000 grant from the National Institute of Justice.

UNLV Center for Crime and Justice Policy director William Sousa says he's studying how cameras change interactions between officers and the people they encounter.