A prominent Denver civil-rights law firm has announced that it is preparing a lawsuit on behalf of Greg Heard, a homeless man who says he was trying to surrender to a Denver police officer when he was tased in an episode caught on a body-camera video . A former SWAT team leader believes Heard’s tasing represented “a textbook use of force,” but Michael Berry, a retired police officer who currently trains law enforcers, strongly disagrees. He breaks down the clip, on view below, and notes that the officer’s use of unprovoked profanity before pulling his taser’s trigger helps explain how incidents like this one can result in excessive force against a suspect and injury or worse to police.