The king of torts - John Grisham

Clay Carter, a public defender in Washington, D.C., reluctantly takes on the case of Tequila Watson, a man accused of a random street killing. Watson insists that he somehow was not in control of his body when he pulled the trigger, a story which Clay tries to dismiss but cannot get out of his mind. Clay tries his best to help Watson, venturing into the capital's most dangerous slums in search of evidence. Clay finally gets a subpoena forcing drug rehabilitation centers to hand over Watson's medical records, as well as those of another man accused of a similar murder.