Clark v. Arizona

Brief Filed: 1/06
Court: United States Supreme Court
Year of Decision: 2006

Read the full-text amicus brief (PDF, 140KB)


At issue is the scope of the constitutional duty of states to allow evidence of sanity to be used as a defense in criminal cases relevant to the intent element of a charged crime

Index Topic

Insanity Defense


Defendant was charged and convicted in a bench trial of the first-degree murder of a police officer. All experts agreed that Clark suffered from schizophrenia, paranoid type, and was actively psychotic at the time of the crime. Nevertheless, he was found guilty and sentenced to life in prison. He appealed his sentence and conviction, inter alia, on the grounds that the Arizona insanity defense statute violated due process and that, following established Arizona law, the trial court failed to consider the evidence of Clark’s mental defect in determining whether he had the requisite mens rea to commit first-degree murder.

APA's Position

APA joined with the American Psychiatric Association and the American Academy of Psychiatry to file a brief in support of the petitioner. The joint brief argues that 1) due process prohibits a state from categorically barring consideration of evidence of mental disorders relevant to the intent element of the charged crime, 2) substantive due process analysis strongly supports a constitutional rule barring serious criminal punishment of a defendant who, because of mental disorder, lacked a rational appreciation of the wrongfulness of his conduct, and 3) Arizona law comports with substantive due process if it is broadly enough construed. The brief provided APA with an opportunity to educate the Court about mental illness, how it can affect human behavior; and, ultimately, how it can undermine notions of culpability that form the foundation of the criminal law’s justification for punishment. The brief also was designed to assist the Court in understanding how expert evidence about mental disorders, presented by qualified professionals, is both reliable and relevant to the issues raised by mens rea requirements, and how mental disorders can bear directly on an individual’s beliefs, understanding of what he is doing, his knowledge and, hence, his intent.


The U.S. Supreme Court ruled that a state may constitutionally limit the insanity defense to prove that the defendant did not know the wrongfulness of his acts and—of greater significance—that it may exclude psychological or psychiatric testimony in certain circumstances on the ground that it has the potential to confuse or mislead the jury.