The Supreme Court today upheld Arizona’s insanity defense law, ruling against Eric M. Clark, who killed a police officer in 2000 at a routine traffic stop. Clark, who had been diagnosed with paranoid schizophrenia before the incident, believed that his locality had been taken over by aliens and that he was being held captive and tortured. Clark argued that the Arizona legislature had wrongly narrowed its insanity standard in 1993. The law says that to prove insanity, a defendant must establish that “he was afflicted with a mental disease or defect of such severity that he did not know the criminal act was wrong,” said the court’s summary of the case.
In a 5-to-4 ruling, Justice David Souter said that Clark’s due process rights were not violated by the revised law. “Clark can point to no evidence bearing on insanity that was excluded,” said the court’s summary. The majority said that Arizona has the authority to define its presumption of sanity, and that its practices help avoid confusion and misunderstanding on the part of jurors. Souter was joined by Chief Justice John Roberts, and Justices Antonin Scalia, Clarence Thomas, and Samuel Alito. Justices Anthony Kennedy, John Paul Stevens, and Ruth Bader Ginsburg dissented; Justice Stephen Breyer issued a partial dissent.