Amends Rule 12 of the Federal Rules of Criminal Procedure to authorize a new plea of "guilty but insane" for any criminal defendant whose actions constitute all necessary elements of the offense charged but who lacks the requisite state of mind as a result of mental disease or defect.

Adopts the current notice provisions for a defense of insanity for the new plea of guilty but insane.

Permits the jury or the court in a non-jury trial to find a defendant guilty but insane. Requires the court in any such case to hold a hearing to determine the present mental condition of the convicted person. Directs the court to commit such person to the custody of the Attorney General upon a finding by a preponderance of the evidence that the person is presently suffering from a mental disease or defect as a result of which release would create a substantial danger to himself or to the person or property of another.

Directs the Attorney General to release such person to a State which will assume responsibility for his custody and treatment or otherwise to hospitalize such person in a suitable facility.

Requires the court to hold a hearing upon the certification by the director of the facility that such person's release will no longer create a substantial danger to himself or the person or property of another. Directs the court to order the discharge of a person who is found to have recovered.

Provides for the hospitalization of persons found guilty, imprisoned persons, and persons due for release, who are found to suffer from mental disease or defect.