Carthage, N.C. — A state toxicologist testified Thursday that the man charged with opening fire inside a Carthage nursing home two years ago had several prescription drugs in his system at the time of the rampage.

Robert Kenneth Stewart is charged with eight counts of murder in the March 29, 2009, shootings at Pinelake Health & Rehab that left seven patients and a nurse dead and three other people wounded. He could be sentenced to death if convicted.

Stewart submitted to a blood test about 9½ hours after the shootings, and tests showed he had the antihistamine Benadryl, the anti-depressant Lexapro and the sleep aid Ambien in his system, according to Richard Waggoner, a toxicologist with the State Bureau of Investigation.

Waggoner said there was also an indication of the tranquilizer Xanax in Stewart's blood.

Defense attorney Jonathan Megerian told jurors last week that Stewart overdosed on Ambien the night before the shootings, which put him in a hypnotic state that left him powerless over his actions. Stewart doesn't recall what happened the day of the shooting and can't be held legally responsible, Megerian has argued.

A prosecutor asked Waggoner Thursday whether someone could calculate the amount of Ambien in a person's blood from nine hours earlier.

"Not with any type of accuracy," Waggoner replied, noting that people eliminate the drug from their systems at different rates.

The SBI lab only tests for the presence of drugs, he said, adding that analysts don't quantify any precise amounts.

Megerian said during cross-examination that Moore County prosecutors never sent Stewart's blood sample to a private lab for review. The defense team did, he said, and the results showed Stewart had 12 times the normal dose of Ambien in his system.

Other crime-scene technicians testified Thursday about the clothing Stewart was wearing at the time of the shootings and about his rifle.

Because of a schedule conflict for one of the jurors, the trial was expected to take Friday off and resume next Monday.

Stewart's former wife, Wanda Neal, is expected to testify next week.

Megerian said he has some concerns about Neal's competency and said Superior Court Judge James Webb might need to hear her testimony outside of the jury's presence first before deciding whether to allow it.

Neal tried to commit suicide by overdosing on medications on July 31 – the day before Stewart's trial began – and was treated at FirstHealth Moore Regional Hospital until Tuesday night, when she was released, prosecutors said.

She signed a consent order Thursday to allow Megerian to review all of her medical records since March 2009.

Prosecutors have argued that Stewart was abusive and controlling of Neal, prompting her to leave him in the weeks before the shootings. He went to Pinelake, where she worked, to track her down and was so heavily armed that nothing was going to stop him, prosecutors have said.