A former Michigan state trooper was convicted of involuntary manslaughter on Wednesday, nearly two years after he fired a Taser at a teenager on an all-terrain vehicle who then crashed and died.The teenager, Damon Grimes, 15, was illegally riding the A.T.V. in a residential area of Detroit in August 2017. State police officers followed in a patrol car to get him to pull over. When he did not immediately do so, the officer in the passenger seat of the patrol car pulled out his Taser and stunned Damon.Video footage of the episode showed the A.T.V. veering toward the side of the road. The teenager crashed into the back of a parked truck and died shortly thereafter.