States are free to decide for themselves how and when to provide an insanity defense for criminal suspects.
In a 6-to-3 decision announced Thursday, the US Supreme Court declined an invitation to set a national constitutional standard for those who claim reduced responsibility for a crime because of mental illness.
The decision leaves in place a patchwork of different insanity defense standards from one state to another.
The action came as the high court let stand the murder conviction of an Arizona man who claimed he should not have been found guilty and sentenced to life in prison for the June 2000 shooting death of a Flagstaff police officer.
Lawyers for Eric Clark say the then 17-year-old believed the police officer he killed was an alien from outer space. They say he belongs in a mental hospital rather than a state prison.
The Arizona courts disagreed, rejecting his insanity defense and finding that despite his mental illness, he understood that it was wrong to kill a police officer.
In challenging his conviction, Mr. Clark's lawyers attacked Arizona's insanity-defense statute, saying it violated US constitutional due process safeguards. Specifically, they said Arizona's law prevented them from presenting defense evidence and testimony about the defendant's diminished mental capacity to fully appreciate the nature and quality of his alleged criminal acts.
Under Arizona's insanity statute, the sole test is whether the mental disease or defect is so severe that the defendant did not know his or her criminal acts were wrong.
Lawyers for Arizona and the US solicitor general argued that there was no constitutional bar to Arizona's decision to streamline its insanity law by dropping consideration of a defendant's diminished capacity.
On Thursday, the Supreme Court agreed.
"Arizona's rule serves to preserve the state's chosen standard for recognizing insanity as a defense and to avoid confusion and misunderstanding on the part of jurors," writes Justice David Souter for the majority.
"Not every state will find it worthwhile to make the judgment Arizona has made, and the choices the states do make about dealing with the risks posed by mental-disease and capacity evidence will reflect their varying assessments about the presumption of sanity as expressed in choices of insanity rules," Justice Souter writes.
In a dissent joined by Justices John Paul Stevens and Ruth Bader Ginsburg, Justice Anthony Kennedy says the rule is irrational because it prevents a defendant from fully explaining at trial why he or she could not have committed the crime because he or she suffered from a mental illness and was thus unable to have formed the criminal intent necessary to violate the law.
"It is unclear ... what would happen in this case had the defendant wanted to testify that he thought Officer Moritz was an alien," Justice Kennedy says. "If disallowed, it would be tantamount to barring Clark from testifying on his behalf to explain his own actions."
As a result, Kennedy says, "the rule forces the jury to decide guilt in a fictional world with undefined and unexplained behaviors but without mental illness."
The decision stems from the June 12, 2000, murder of Flagstaff Police Officer Jeffrey Moritz. The incident occurred at 4:51 a.m. when Officer Moritz responded in uniform and in his marked patrol car to 911 calls from residents complaining that a pickup truck was circling the block while playing loud rap music.
The officer activated his emergency lights and pulled the truck over. Within a minute there was an exchange of gunfire. Moritz was shot in the chest and died.
Both sides of the case agree that Clark was driving the truck and that Clark shot and killed the policeman.
Prosecutors introduced evidence at trial that Clark had earlier told a friend that he was thinking of creating a disturbance to attract police officers to a particular location so he could shoot them dead. They said the murder of a law-enforcement officer was therefore a premeditated act.
Defense lawyers countered that prior to the shooting, Clark had been experiencing mental illness for about a year and a half. They said his condition was growing worse. He was admitted to a psychiatric hospital, but was later released. Clark's parents tried to have him recommitted to a hospital, and during the two days before the shooting, they contacted five facilities to take their son, according to court briefs.
Clark believed that Earth had been invaded by aliens and that they'd taken over Flagstaff, the briefs say. He believed they were trying to capture and kill him by poisoning his food. He started to eat at a local Sizzler because he thought he would be safe from poisoning by eating with the general public, court briefs say.
After the shooting, a judge determined Clark was not mentally competent to face trial. He was treated for nearly three years at the Arizona State Hospital before his competency was restored. Then he was placed on trial for murder.
At trial, his lawyers argued that he should be found "guilty except insane" under Arizona law, and sent to a hospital rather than a prison. But the trial judge found that Clark could be held responsible and punished for his crime. A state appeals court upheld that decision.
On Thursday, the Supreme Court upheld the Arizona rulings.