December 22, 2014 9:49 AM EST

The lack of video evidence in last summer’s fatal police shooting of Michael Brown in Ferguson, Mo., has accelerated a movement to equip cops with cameras on their uniforms. Experts say more than 5,000 of the nation’s 18,000 police departments are now using or testing the devices–including big-city forces in Los Angeles, New York City and Washington–as part of an effort to mend often frayed ties with citizens. Since Ferguson, Vievu, the largest manufacturer of the cameras, says the number of departments testing its devices is up 70%, while monthly sales are at record highs. “In 10, 15 years,” says Arthur Lurigio, a criminal-justice expert at Loyola University Chicago, “I think we’ll be talking about the camera in the way that today we talk about the baton or the badge.”

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