Contrary to uninformed opinion, defendants found not guilty by reason of insanity are not simply released from custody. They are generally committed to mental hospitals where they can be confined for longer than their prison terms would have been. In the case of Jones v. United States, the Supreme Court in 1983 backed this proposition, ruling that the sentence that criminal defendants would have received had they been convicted should have no bearing on how long they could be committed to a mental hospital.
After Hinckley, many states changed their commitment policies to ensure that a defendant found not guilty by reason of insanity would be required to stay in a mental hospital for a certain period of time for evaluation following acquittal. Previously, no time was specified. Also, several states changed the burden of proof for release from the state to defendants.