A former Michigan state trooper is facing a prison sentence for involuntary manslaughter for firing a Taser at a Detroit teenager who crashed an all-terrain vehicle and died.

Mark Bessner quit the state police after the 2017 incident. He's returning to court Monday for his sentence, about a month after his conviction .

Prosecutors say Bessner "committed an unspeakable act" when he fired his Taser from a moving patrol car and struck Damon (Da-MAHN') Grimes.

Bessner's lawyer said the officer believed Grimes had a gun in his waistband, but the 15-year-old didn't have a weapon.

Bessner, who is white, didn't testify at the second trial. During his first trial, which ended without a verdict, he said he was "shocked" to learn that the black teen didn't have a gun.