The presentation opens with a description of John Hinckley, Jr.'s attempt to assassinate President Reagan and the key elements of Hinckley's subsequent successful insanity defense. This trial is considered the focal point of the renewed debate over the historic and current use of the insanity defense. Since the evolution of the principles of the insanity defense in American courts originated in the M'Naghton case in Great Britain, this case is reviewed along with the insanity-defense principles that emerged from it. The current American Law Institute (ALI) insanity rule is then compared with the M'Naghton rule, with the ALI rule considered to be broader and more flexible, encompassing the use of the concept of diminished capacity within the insanity defense. Attention is given to what happens to a defendant acquitted by reason of insanity, namely, the mental health treatment that may be required and the nature and length of confinement accompanying such treatment, along with procedures required for release. Arguments against the insanity defense are then presented, including the early release of dangerous persons from psychiatric facilities, a jury's inability to judge between conflicting psychiatric testimony about a defendant's mental state at the time of the offense at issue, the subjectivity of psychiatric opinion, and the fact that only rich defendants can afford to use the insanity defense, since it involves costly psychiatric testing and testimony. Arguments for the continued use of the insanity defense are based in the concept of fairness and justice, which holds that a person whose mind is clouded by mental illness at the time of an offense cannot be said to have the criminal intent required for legal guilt. Attempts to revise the insanity defense, notably the development of the verdict of guilty but mentally ill, are considered, and attention is given to Oregon's effort to improve its system of handling mentally ill people in trouble with the law. A subject index and a recommended reading list with 17 entries are provided.