The insanity defense does have a place in the justice system because some people honestly didn't know what they were doing was wrong at the time a crime took place. Sometimes, the insanity defense is abused by desperate defense lawyers trying to get lighter sentences for clients. However, for those who are clinically insane the defense for such a malady must be there to protect someone's life as opposed to giving a defendant the death penalty.
The insanity defense has a legitimate place in criminal justice. There are people who truly need mental health help. Our criminal justice system usually imprisons people instead of getting them the mental health help they could truly use. Many of these people would benefit from extensive therapy. Prison does nothing to help these people. Prison is no different than locking an animal in a cage.