Eric Clark, a 17-year-old with schizophrenia in Flagstaff, Ariz., was convinced that aliens in the form of policemen were coming to get him. Late one night he hopped in his brother's pickup truck and circled the block with the radio blaring. When an officer arrived, Clark shot and killed him.
Five years ago, the U.S. Supreme Court rejected his insanity defense and agreed with Arizona prosecutors that a paranoid schizophrenic who has delusions can nonetheless be held accountable for his crimes. Clark understood it was wrong to kill a police officer, the court concluded, even if he may have thought he was killing an alien.
Legal experts say the Clark case and similar rulings make it highly unlikely that Jared Lee Loughner could successfully plead insanity to escape punishment in the shootings of 19 people, including Rep. Gabrielle Giffords, in Tucson this month.
However, Loughner would stand a good chance of escaping the death penalty because of mental illness, the same experts say. Since the shootings were seen by dozens of witnesses and captured on video, they say, the only question in his case is what punishment he deserves.
It's not clear whether the 22-year-old Loughner has been formally diagnosed with a mental disorder, but his incoherent rants — well-documented in online videos — create a troubling portrait.
"The public is hostile and the courts are hostile to a mental health defense," said David Bruck, a law professor at Washington and Lee University and a nationally recognized expert in capital cases. "An insanity defense is almost never successful if the prosecution chooses to fight the issue."
However, "it seems clear that mental illness will play a big role in this case," said Richard Bonnie, a professor of law and psychiatry at the University of Virginia. "The ultimate issue will be whether Loughner receives a death sentence, and on that issue, the mitigating evidence of his mental illness is likely to be the determinative factor."
The law has long struggled with how to punish criminals who appear to be mentally deranged. For more than 700 years, English criminal law has recognized an exception for an insane person. A crime involves not just a wrongful act, but an intent to do wrong, and it was said that a "madman" did not understand his actions were wrong.
But while this principle is well accepted, the insanity defense has always been controversial. The most famous case in the history of insanity law was in 1843, when a Scottish woodcutter named Daniel McNaughton was acquitted by reason of insanity of the murder of a British official after medical experts testified that McNaughton suffered from delusions that he was being persecuted.
The British public and Parliament were outraged. The House of Lords convened and set down what became known as McNaughton rules: To prove insanity, the defense must show that the defendant had a "disease of the mind" at the time of the crime that left him unable to "know the nature and quality of the act he was doing," or that he did not understand it was wrong.
These rules were standard in American law through the middle of the 20th century. But advances in psychiatry persuaded many courts to adopt a more lenient approach to mental illness. Some said a defendant could be excused if an "irresistible impulse" caused him to act. Others were excused if they lacked a "substantial capacity" to understand their crimes.
But acquittals in highly publicized cases prompted a sharp backlash against the use of mental-health evidence.
In 1979, Dan White, a former San Francisco supervisor who wanted his job back, was convicted of voluntary manslaughter rather than first-degree murder for killing Mayor George Moscone and Supervisor Harvey Milk after pleading diminished capacity due to depression, citing his unusual consumption of sugary foods as evidence. That argument became widely known — derisively —as the "Twinkie defense." Public outrage led to California abandoning the diminished-capacity defense.
The tide against use of the insanity defense turned dramatically in 1982 when John Hinckley Jr. was acquitted by reason of insanity of the attempted assassination of President Reagan.
In response, Congress tightened the law on insanity, dropped the focus on the defendant's mental condition and said his lawyers must prove by "clear and convincing evidence" that he did not know his acts were wrong. Arizona also tightened its law and said that a defendant's mental illness did not shield him from criminal punishment.
Loughner is expected to face federal and state prosecution for the Tucson shootings. The Supreme Court's ruling in Clark vs. Arizona will be "highly relevant" to both, said David Goldberg, an Arizona lawyer who represented Eric Clark. "Even if you have a mental illness and it affects what you do, that doesn't matter," he said, summing up the ruling. "All that counts is if you knew right from wrong."
After shooting the police officer in Flagstaff, Clark ran away, and that was seen as proof he knew he had done wrong. He was sentenced to life in prison.
In Loughner's case, defense attorney Judy Clarke would have to show that her client did not know his actions were wrong. Evidence that Loughner was paranoid or delusional would not be enough to shield him from punishment, under either federal or Arizona law.
Such evidence may be good enough to shield him from a death sentence, however, if the Justice Department or the state asks for one.
"It makes sense to use an insanity defense in a case like this if the government seeks the death penalty," Goldberg said. "He may not be legally insane, but you would be educating the judge and jury as to why his actions occurred."
In the sentencing phase of a capital case, the jury must unanimously agree that death, not life in prison, is the proper punishment. Evidence of a defendant's troubled mental state commonly results in the jury voting against execution.