Brief Fact Summary. When Clark, who was without dispute a paranoid schizophrenic, was not allowed to present evidence of diminished capacity in his trial for first-degree murder, he pleaded violation of his right to due process of law.
Synopsis of Rule of Law. A state does not violate due process of law by preventing the introduction of evidence showing diminished capacity by a criminal defendant.
Issue. Does a state violate due process of law by preventing the introduction of evidence showing diminished capacity by a criminal defendant?
Held. (Souter, J.) No. A state’s prohibition of the introduction of diminished mental capacity by the defendant in a criminal case does not violate due process. The state prohibition applies only to evidence regarding mental capacity and mental disease, usually based on expert testimony, rather than observation. Such a restriction, provided it has a good reason, is not a violation of constitutional rights, as the benefits outweigh the loss of the evidential value. Another point is that the consideration of such evidence is limited if the evidence is disallowed as a whole. Evidence regarding mental disease and mental capacity presents risks which can be limited by allowing only the insanity issue to be considered, upon which the burden of evidence rests on the defendant. Some of these risks are the debatable nature of some diagnoses of mental disease, the danger of the evidence being misleading and the risk of ascribing a greater level of certainty to the evidence of mental capacity than the experts intended to communicate. Firstly, the diagnosis does not reveal the uncertainty about what actually defines mental illness, which is not always agreed upon by mental health experts; secondly, the evidence of mental disease may lead jurors to mistakenly suppose that the defendant lacks reasoning, thought, willpower or moral discrimination because of his mental illness, when such may not be the case at all, even if the diagnosis is broadly correct, and the defendant is undisputed to belong to such a category; and finally, the expert opinions carry undeserved weight when they supplement the diagnosis of mental capacity with their judgment of the defendant’s mental capacity, as to his inability to understand right or wrong, or to think through an action in the manner necessary to establish the mensrea. The danger is always present that in this type of evidence, unlike observational evidence, the expert will not be able to define the exact state of mental thought or capacity at the moment of the offense despite the most careful examination. The legal categories that are responsible for the definitions governing mental capacity judgments are not identical with psychological categories that define the psychiatrist’s judgments. These practical and theoretical problems pose a substantial risk that the expert testimony regarding mental capacity evidence will have an apparent but unintended and unreal authority. This risk and the inherent difficulty of evaluating the importance of evidence regarding mental disease are the basis of Arizona state’s decision to limit expert psychological or psychiatric evidence to consideration on the insanity issue, on which the defendant, as the party which stands to benefit, has the burden of persuading the court. The verdict is affirmed.
The Washington court stated that the Constitution is violated by arbitrary rules that prevent whole categories of defense witnesses from testifying on the basis of a priori categories that presume them unworthy of belief.View Full Point of Law
In this case, the Court made the point that while not every state will find it necessary to exclude mental capacity or mental disease evidence, it is still a sensible choice by Arizona as the reasons given for channeling the evidence are to limit the risks while still preserving due process of law for the accused person.