Insanity Defense- is it Rational?

The insanity defense continues to evolve and be shaped by our knowledge of cognition, mental health and effectivity of treatments and punishments, as well as cultural changes and response by the public to outcomes from the criminal justice system.

We have had immense gains in our understanding about mental illness since the M'Naghten Rule was established, although public sentiment continues to lag this knowledge.  If you consider the treatments that have included electric shock therapy, lobotomy and other practices considered barbaric today, how society has evolved in the understanding of mental illness, and the rights of the mentally ill, has also evolved.  Yet, when the criminal justice system has "gone too far", public outcry about guilty going unpunished results in a backlash that reverses the direction away from the rights of the accused towards authoritarian punishment. 

I have struggled with the notion of the insanity plea, as I can see both the need for protecting the mentally competent from acts they do not understand, and the need to mete out justice and protect society from violent offenders.

I find it interesting that there are three states (Utah, Montana and Utah) that do not allow the insanity defense.  This seems greatly unfair to me, as there are those who are clearly incapable of understanding their actions, or of subsequently understanding the trial.  This seems like shooting my dog unless it tells me, in flawless English, to "please don't shoot".  How can we hold persons who cannot understand their actions accountable under the law?  Still, I do understand the desire for justice and punishment, to the point of revenge, particularly for the families of victims.  The anguish of seeing someone "walk free" who has been proven guilty in the family's perspective would be a dagger in the mind that would cry out for revenge.

I've lived with the mentally ill, and that's included bipolar disorder, sensory integration disorder, autism, dementia, Altzheimer's and anorexia nervosa.  There's a big difference from being [neurotic, ADD, grumpy, getting your freak on, irrational, jerk, caffeine overdosed, drunk] and hearing voices, thinking bugs are moving under your skin or talking to your long-dead mother who you think is in the room.  You don't punish a baby for filling their diaper, or a deaf child for not responding when you talk to them.  It is a common misconception in education that "all children should be treated the same".  However, my autistic child needed more time and assistance at understanding the questions.  That's not cheating or creating a differing standard, any more than you'd hand a fill-in-the-blank quiz to a blind child, then give them an F when they failed to complete it.  When you're dealing with gaps in mental health where there is no recognition of actions, consequences and/or societal mores, to what end do you punish them?  You might as well punish a child because it rains.

The concept of not executing someone who had become insane after conviction of a capital crime had seemed wrong to me until I studied this topic more deeply.  Now I understand that their insanity would prevent them from mounting a credible defense for appeals, or at least, prevent them from understanding the appeals process.  Still, if they were found insane after being denied their final appeal, I think they should be executed.