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NORMAN, Okla. -- Defense attorneys for a man on trial for a gruesome workplace attack have rested their case, leaving room for rebuttal from state prosecutors.

Alton Nolen stands accused of beheading his coworker Colleen Hufford and stabbing Traci Johnson inside Vaughan Foods in September 2014. Hufford died from her injuries, but Johnson survived.

Dr. Shawn Roberson, a forensic psychologist who met with Nolen after a court-ordered pre-trial evaluation, was one of two rebuttals called by the state Thursday. He testified the suspect showed no signs "whatsoever" of a mental illness.

According to Roberson, Nolen was cooperative and never shut down during the evaluation despite refusing to answer some questions. He told the court Nolen was narcissistic, rather than 'grandiose' as described by the defense's mental health experts. 'Grandiose' is a sign of mental illness, according to Roberson.

The second rebuttal witness called Thursday was Dr. Jarrod Steffan, a forensic psychologist who also met with Nolen in the past. He testified Nolen suffers from a personality disorder with anti-social traits, pulling examples of his apparent 'controlling' tendencies.

The defense team includes attorneys Mitch Solomon and Shea Smith. They called a total of four witnesses to the stand, including two mental health experts who testified Nolen is suffering from schizophrenia and was insane during the time of the attacks.

Dr. Anita Jeanne Russell, a Tulsa-based psychologist, met with Nolen in the spring of 2015 for an evaluation.

"I found him to be quite delusional," Dr. Russell recalled in court.

Another witness called by the defense was religion professor Dr. Robert Hunt of Southern Methodist University. He told the court Nolen "did not have a firm grasp of Islam", after Nolen justified the beheading as correct by the Quran for feeling oppressed at work.

State prosecutors called more than 20 witnesses to the stand during their presentation of evidence in the first three weeks of trial. Many of the witnesses were former colleagues of Nolen and investigators who interviewed him after the September 2014 attack. They testified Nolen never appeared to be hallucinating or hearing voices.

Cleveland County district attorney Greg Mashburn says the state has one more rebuttal witness who testify Friday. After that, the jury will begin deliberations.

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