The court overturned a state appeals court ruling from last year that gave Donyil Anderson a new trial. He was sentenced to life in prison for the 2008 killing of Stacey Hosey. He also injured Hosey's boyfriend, Branden Beavers-Jackson.
Anderson argued on appeal that he deserved a new trial because of faulty instructions to the jury about how his mental state may have been affected by the drug Strattera, which he was taking to treat attention deficit hyperactivity disorder.
The appeals court sided with Anderson last year. It said the jury instruction falsely suggested that taking a prescription drug is voluntary and cannot lead to a mental defect.
But in a 5-2 decision, the Supreme Court said the jury instruction was proper and upheld Anderson's conviction.
"Nothing in our case law supports the proposition that the consumption of prescription medication may form the basis for an insanity defense," Justice Michael Gableman wrote for the majority. Also, Gableman wrote that the court has never distinguished between the use of prescription drugs and illegal drugs in the context of an insanity defense, and there is no reason to do so now.
Anderson's attorney, assistant state public defender Bill Schmaal, said it didn't make sense for the court to conclude that taking a mind-altering prescription drug couldn't contribute to a person's behavior.
"Psychiatric medicine is designed to change the way a person's brain chemistry operates," Schmaal said. "To say there is no difference between that someone who takes illegal drugs to get intoxicated is virtually incomprehensible to me."
The court said if it had agreed with Anderson, future defendants could argue that taking prescription medicine is a legitimate defense for illegal behavior.
Chief Justice Shirley Abrahamson and Justice Ann Walsh Bradley dissented. They argued that the law allows for a defendant to raise an insanity defense on the basis that their behavior was caused by taking medicine that's prescribed by a doctor.
Dana Brueck, spokeswoman for the state Department of Justice which prosecuted the case, had no comment.