Judge John Scotillo ruled Tuesday that Karl Sneider of Palatine suffered from mental illness and "lacked substantial capacity to appreciate the criminality" of killing his 49-year-old mother, Kathryn Sneider.
During four days of testimony, four doctors said Sneider was schizophrenic and suffered from delusions and hallucinations.
According to court testimony, Sneider told police he was Jesus Christ, his mother was Satan and that her death in January 2003 signaled the triumph of good over evil.
According to police and prosecutors, the two got into a fight after she told him he should be committed to a mental hospital. He then stabbed her, cut off her head with a kitchen knife and put her head on the front porch.
The next morning he stole a neighbor's car and crashed it before police tracked him down, reports said.
Scotillo ordered Sneider to be evaluated by mental health experts within 30 days. The judge will then determine the number of years and what type of mental-health supervision Sneider will receive. He will remain in Cook County jail until then.
Outside the suburban Chicago courtroom, relatives were divided on the ruling.
Some wanted Sneider to go to prison and shouted at his father, Warner, who said his son was a troubled man.
"Don't you understand he's sick?" Warner Sneider said to relatives. "He's going to a mental institution, he's not going to be on the street."
But Sandy Larson, Kathryn Sneider's sister-in-law, said "everybody should be afraid" of her nephew.