Electra Glide in Blue (1973)

An Arizona motorcycle cop patrolling the desert highways longs to move up to Homicide. When a death first treated as suicide begins to look like murder, he gets the chance he has been waiting for, with a superior officer backing his instincts. As the investigation into a hermit’s mysterious death unfolds, he must face uneasy truths about his ambitions, his judgment, and the people around him.