U.S. Supreme Court Decision on Insanity Defense: Clark v. Arizona



Statement by the Treatment Advocacy Center on the ruling: "We as a nation need to finally stop counting on the insanity defense to keep mentally ill people out of prison and start counting on treatment to keep people from committing crimes in the first place ..."

June 29, 2006: The Court ruled that Arizona's law on the insanity defense does not violate constitutional due process.

From The ruling in Clark v. Arizona (05-5966) was written by Justice David H. Souter and divided the Court 6-3, although Justice Breyer also filed a partial dissent and partial concurrence. The ruling upheld what is called the "Mott rule" in Arizona, barring psychiatric evidence of a mental disorder short of insanity to offset prosecution evidence of criminal intent. The ruling also upheld Arizona's definition of the insanity defense.


In hearing Clark v. Arizona (docket 05-5966), the US Supreme Court is considering a direct challenge to the insanity defense for the first time in more than 25 years.

Where we stand: The failure of the system to avert this tragedy comes down to badly written and poorly used laws and policies for helping people with severe mental illnesses too ill to make informed treatment decisions. In places with more humane laws and policies that actually get implemented, the results are different for people like Eric Clark. Of participants in New York’s assisted outpatient treatment program, for instance, 83% fewer experienced arrest and 87% fewer experienced incarceration. Violent episodes were reduced. Medication compliance improved. Quality of life is restored. Arizona has a similar law, but it is vastly underused. Cases like Eric Clark’s are the result. Laws restricting mental illness treatment are insane. Perhaps one day the Court will consider the constitutionality of condemning people to psychosis.


Eric Clark was convicted of first-degree murder for the June 21, 2000, shooting death of Flagstaff, Arizona, police officer Jeff Moritz, who was shot while making a traffic stop. Clark, a young man with untreated schizophrenia, was delusional and thought that aliens had invaded Flagstaff. Like about half of those with schizophrenia, Clark’s brain disease prevented him from understanding that he was ill.

At trial, Clark's family testified that he had been exhibiting symptoms of severe paranoia for years before the shooting, and that they had been unable to access long-term treatment for him, despite many attempts.

Clark was sent to prison on October 3, 2003, for a minimum of 25 years. Once in prison, Clark refused his psychiatric medications. In February 2005, the Court of Appeals upheld Clark's conviction. His attorney then requested the Arizona Supreme Court hear the case in an attempt to get Clark out of prison and into the state mental hospital.

It is worth noting that Eric Clark’s parents are still fighting for him to get treatment, now from behind bars. This is the same battle they were fighting before he shot and killed Officer Moritz.


It has been recognized for centuries that criminal defendants who lack understanding of their actions, and therefore lack moral culpability, should be treated differently by the legal system than other defendants. English common law has recognized insanity as a bar to criminal culpability for more than 700 years.

When John Hinckley was found not guilty by reason of insanity for shooting then-President Ronald Reagan in the early 1980s, the public reaction was that the law was not strong enough. This led to widespread reassessment of the insanity defense.

Underlying these hundreds of years of jurisprudence is an unwavering belief that the insane act without an understanding and appreciation of the consequences of their behavior. This lack of awareness requires, from a constitutional standpoint, that some provision be made for the severely mentally ill to be treated differently under criminal law.


Recent scientific findings about the nature and effect of severe mental illnesses are essential in the due process consideration of any criminal defense based on a person’s ability to comprehend the nature, quality or wrongfulness of his conduct. It is now also known that among the symptoms of these diseases is the neurological deficit anosognosia, which prevents affected individuals from knowing they are ill and thus from obtaining treatment. Anosognosia is a biologically-based inability to appreciate one’s own illness. Thus, it differs from denial, which is a psychologically-based coping mechanism common within the non-mentally ill population.

Anosognosia can prevent a mentally ill person from comprehending—and thereby treating—his own illness. Lack of treatment is known to increase the risk of this person committing a violent act. Consequently, the moral and legal doctrines of the last several centuries dictate that such a person be afforded a defense based upon his mental and, as society now knows, physical ailment.


 (1) Whether Arizona's insanity law, as set forth in A.R.S. § 13-502 (1996) and applied in this case, violated Petitioner's right to due process under the United States Constitution, Fourteenth Amendment?

(2) Whether Arizona's blanket exclusion of evidence and refusal to consider mental disease or defect to rebut the state's evidence on the element of mens rea violated Petitioner's right to due process under the United States Constitution, Fourteenth Amendment? Cert. Granted 12/5/05


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