Many states allow a jury in a criminal trial to return a verdict of “Not Guilty by Reason of Insanity.” The law in Kootenai County and elsewhere in Idaho does not allow a complete insanity defense.
Idaho statute 18-207 specifically states that a “mental condition shall not be a defense to any charge of criminal conduct.” Instead, after the judge imposes the sentence, the mentally ill defendant may be sent to a confined facility that treats mental illness rather than being sent to a regular prison. The discretion is up to the sentencing judge.
Even if an expert (psychiatrist or psychologist) testifies that the defendant did not have the mental ability to conform his actions to the requirements of the law, the insanity defense would not apply.
However, the above harsh law does not totally foreclose a defense of insanity under certain circumstances. For example, in every criminal case, the prosecutor has the burden of proof as to all elements of the crime. For many crimes, part of the burden of proof involves proving the intent of the defendant. Thus, for example, if a person has been charged with killing a person, but he is suffering from psychotic hallucinations and believed that the person he shot was actually a grizzly bear, the prosecutor may not be able to prove that the defendant acted with the intent to kill a human being.
As a practical matter, in cases where a defense attorney can demonstrate to the prosecutor that the defendant is seriously mentally ill, the prosecutor will sometimes avoid trial and enter into a plea bargain in which the defendant is still punished, but the primary goal of the sentence would be to alleviate his mental illness.