16-year-old Donovan Nicholas was found guilty of aggravated murder and murder in the death of 40-year-old Heidi Fay Taylor in April 2017.
Nicholas, who was tried as an adult, originally pleaded not guilty by reason of insanity back in December.
He was sentenced to three years in prison on a gun specification, plus 25 years to life. He is not eligible for parole until he serves 28 years in prison.
A forensic psychologist, Daniel Hrinko, testified a year ago in Champaign County Family Court that Nicholas suffers from a dissociative disorder.
In a 911 phone call obtained by this news organization, Nicholas can be heard telling dispatchers that another personality killed the woman, who was stabbed more than 60 times and then shot in their home.
"I just killed my mother," Nicholas can be heard saying on the recording. "It wasn't me who, who, it wasn't me who killed her. It was Jeff. Jeff. I'm sorry."
He said Jeff was another personality.
"This is going to be really hard to explain but I kind of have another person inside me," Nicholas says on the recording.
Defense attorney Darrell Heckman said it's believed Nicholas' alleged split personality "Jeff" is a character from an internet horror series "Jeff the Killer," who is known for fictitious brutal killings on the shows.
Nicholas, who was 14 at the time of his arrest, will be sentenced in Champaign County Common Pleas Court.
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