Whether Michigan's guilty-but-mentally-ill verdict violates due process because jurors cannot fairly distinguish mental illness from legal insanity.
Holding
No. The statutory distinction between mental illness and legal insanity is sufficiently clear to permit a fair trial.
Reasoning
Michigan's statute permits a guilty-but-mentally-ill verdict only when the factfinder finds beyond a reasonable doubt that the defendant committed the offense, was mentally ill when doing so, and was not legally insane. Mental illness is a substantial disorder significantly impairing thought, mood, judgment, behavior, reality recognition, or ordinary functioning. Legal insanity is the more demanding condition in which mental illness causes a lack of substantial capacity to appreciate wrongfulness or to conform conduct to law.
The Court viewed the statutes as creating a continuum: every legally insane person is mentally ill, but not every mentally ill person is legally insane. Thus, the verdict does not add an irrelevant inquiry; it requires the factfinder to decide whether the defendant's mental impairment crossed the statutory threshold that eliminates criminal responsibility.
The additional inquiry may make some cases harder, especially where the evidence lies close to the line between illness and insanity. But difficult distinctions are not beyond a jury's competence. The Court compared this task to other familiar criminal-law distinctions, such as differentiating an intent to kill from an intent to do great bodily harm. Policy objections to the Legislature's choice of verdict belonged to the Legislature, not to a due-process challenge.