On a sunny Friday afternoon in July 2014, James King, a 21-year-old college student, was walking to a summer job in Grand Rapids, Michigan, when he was accosted by two unshaven men wearing jeans and baseball caps who asked his name and grabbed his wallet. When King tried to flee, the men tackled him, choked him unconscious, and punched him in the face over and over again. The men, it turned out, were cops, and for six years King has been trying to hold them accountable for their actions that day. Next Monday the U.S. Supreme Court will consider whether...