I do not know if Elizabeth Smart kidnapper Brian Mitchell is mentally ill. I do know that the judge said he has no mental incapacity that would prevent him from aiding in his own defense, and the judge is therefore sending him to trial.
The issue of mental illness may again come up at trial, and the American legal system has only a bad way of handling that: Not Guilty by Reason of Insanity.
A mentally ill person can be found Not Guilty by Reason of Insanity (NGRI) if the jury finds that the person was not able, at the time of the crime, to understand the difference between right and wrong. NGRI defenses are rarely successful because most mentally ill people, even when psychotic do understand the difference between right and wrong. John Hinkley probably understood it was wrong to shoot Ronald Reagan, but, gosh, it might've gotten him a date with Jodie Foster. Right and wrong isn't the issue: psychotic reasoning is.
If you 'know' (not think) you are the messiah and the police are trying to kill you, in self-defense (to your psychotic way of thinking) you have to shoot the police first. This is the insane Catch-22 often faced by the mentally ill. They 'know' shooting the police is wrong, but they also 'know' if they don't, the police will shoot them. Because they 'know' the former, they can't be found NGRI. The result is that people who were so mentally ill they couldn't control their actions are sent to jail. That's not anyone's idea of justice.
If an NGRI insanity defense is successful, they are involuntarily hospitalized and treated, usually with medicines that prevent violence. But when individuals found NGRI regain sanity, theoretically, they have to be released. And then they can go off medication and become violent again. Again: That's not anyone's idea of justice. It doesn't help anyone.
What's to be done?
We should replace" Not Guilty by Reason of Insanity (NGRI)" with 'Guilty Because of Mental Illness (GBMI). People found Guilty Because of Mental Illness should be sentenced to treatment for the maximum time-or longer- they would have been sentenced to jail had they been found guilty.
The sentence to treatment could include involuntary inpatient commitment and involuntary outpatient commitment and the patient could be ordered to go from one to the other without any new hearings being required. A case worker, probation officer and doctor would monitor compliance with treatment (much like New York's Kendra's Law) and have the ability to order which form of commitment is needed, depending on the how well the offender is doing.
If mental illness was the cause of the violent act, then treatment is the cure. It's as immoral to incarcerate the mentally ill for an action they couldn't control as it is to let them go off treatment and become violent again. Our current system does both.
Allowing a plea of "Guilty Because of Mental Illness", with mandatory treatment is the only sane approach to treating mentally ill offenders.
(NOTE: The opinions in this piece are the authors and not any organization he may be associated with).