One framework for analyzing moral reasoning in complex situations is Kohlberg's theory of moral reasoning. Kohlberg suggests that as the child matures in terms of moral development, there is a progressive reconsideration of what is right, as well as of the relationship between law and society. The theory suggests the importance of the social environment in stimulating moral reasoning. Kohlberg's work has been criticized because it argues that the conduct in a particular society may be judged only be that society's values. Studies on the My Lai incident in Viet Nam, capital punishment, and abortion suggest that the issue of taking human life appears very different to people at different moral stages of development. A special case of the dilemma of lethal force is found in the police officer's decision to use deadly force in the line of duty. In most States, police officers are allowed to use lethal force when the officer's life is in danger, a civilian's life is in danger, or when a dangerous felon is fleeing from arrest. A moral reasoning study of 24 police officers responding to hypothetical dilemmas dealing with the use of deadly force revealed that the officers of different moral stages viewed the dilemma of taking a human life in distinct philosophic frames of reference. Moral development theory is extremely useful in interpreting the type of rational violence present when the police officer makes the decision to use deadly force. Police departments should use some means of moral reasoning evaluation to select officers entering police work. Eight references are provided.