The insanity defense, called the "not criminally responsible" defense in some jurisdictions, is an affirmative defense that may be asserted in some states in order to seek dismissal of a prosecution, although confinement in a mental institution would then likely result. Also, if conviction of a crime would require registration on a sexual offender registry, many jurisdictions require that a person acquitted solely by reason of insanity register as though that person had been convicted.
The recent trend by states has been to limit or virtually abolish the broad insanity defense. In the states of Idaho, Kansas, Utah, and Montana, their state supreme courts have replaced the insanity defense with a different procedure that only allows a defendant to introduce evidence to negate a specific requirement of intent for a specific crime. In these states the issue becomes one of evidentiary intent, rather than dismissal of the entire case.