CARTHAGE, N.C. — A judge ruled Wednesday that prosecutors must prove that a Moore County man wasn't under the influence of a sleeping medication two years ago when he opened fire inside a Carthage nursing home, killing eight people.

Closing arguments are set for Thursday in Robert Stewart's trial. Stewart is charged with gunning down seven patients and a nurse in the March 29, 2009, shootings at Pinelake Health and Rehabilitation Center. He could be sentenced to death if convicted.

Prosecutors have argued that Stewart went to Pinelake, where his then-wife, Wanda Neal, worked, to track her down and that he was so heavily armed that nothing was going to stop him.

Defense attorney Jonathan Megerian has maintained that Stewart doesn't recall what happened the day of the shootings and can't be held legally responsible.

Megerian told jurors that Stewart was taking several medications and overdosed on the sleep aid Ambien the night before the shootings – a blood test taken hours later showed he had 12 times the normal dose in his system – putting him in a hypnotic state that left him powerless over his actions.

Because the evidence of the Ambien in Stewart's system was presented in the prosecution's case, Superior Court Judge James Webb ruled that jurors must assume Stewart wasn't in control of his actions. To convict him of murder, the judge ruled, jurors must be convinced otherwise by the evidence.

The defense theory, called automatism, differs from involuntary intoxication, which isn't a legal excuse for committing a crime, because evidence has shown that doctors prescribed the Ambien for Stewart.

Webb rejected a defense request to allow the jury the option of convicting Stewart of manslaughter, but they will be allowed to convict him of either first-degree or second-degree murder, depending on whether they believe he planned on shooting his victims.

A second-degree murder conviction doesn't carry the possibility of a death sentence.