Daniel Baker flew into a fit of rage and jealousy moments before he bludgeoned to death 50-year-old Marina Aksman of Vernon Hills in 2010.
However, momentary rage does not fall under the court's definition of insanity and, as a result, the 24-year-old Deerfield man was found guilty but mentally ill in the first-degree murder case Monday morning.
The ruling by Lake County Judge Daniel Shanes means Baker could be sentenced later this year to between 20 years and natural life in prison. However, Baker will receive treatment for any mental issues he is dealing with while incarcerated, prosecutor Ari Fisz said.
"He will either be treated in prison or can be sent to a mental hospital if prison psychologists decide to do so," Fisz explained. "But after any mental treatment is completed in Elgin, he will be returned to prison."
Neither Baker's family nor Aksman's family would comment after the verdict.
Shanes' ruling comes following a seven-day trial in which defense attorneys sought to prove Baker was insane when he killed his girlfriend's mother on April 1, 2010.
Prosecutors alleged Baker murdered Aksman because she tried to end the relationship he was having with her daughter, Kristina.
Baker, who suffers from multiple mental disorders, took off with Kristina Aksman on a four-day drive after the murder. He was arrested in Montana and admitted to the crime during a five-hour interview with investigators, authorities have said.
Defense attorney Ed Genson said he believed it was that confession that pushed Shanes into finding Baker guilty.
"What hurt was the five-hour statement (Baker) made after the occurrence," Genson said. "We have a fine judge here, which is why it is difficult for me to disagree with him on the verdict. The evidence clearly shows (Baker) was insane."
Genson said he will ask for a new trial for Baker. That motion is expected to be argued in late November, before Baker is due to be sentenced.
Genson added Baker's loud, boisterous and often disruptive behavior throughout the trial clearly showed Baker was not fit to be a part of the court proceedings.
"He was the most difficult client I have ever had," Genson said. "He should have been treated (at a mental hospital) in order to be more cooperative with his attorneys during the trial."
Fisz said most of Baker's courtroom disruptions were "for show."
"Judge Shanes is a good judge and saw through those disruptions," Fisz said. "We are very pleased with the verdict."
Due to her own disabilities, Kristina Aksman was not charged in connection with the murder.
Prosecutors showed Marina Aksman left a voice message for Baker in the early morning hours of April 1, telling the Deerfield man he was bi-polar and would not be allowed to see Kristina again.
Shanes said the phone call drove Baker into a fit of rage, pushed him to drive to Aksman's home in the middle of the night, and attack the woman with a baseball bat.
"What the defendant did was vicious and barbaric," Shanes told a silenced courtroom while he read his verdict. "Those messages triggered a homicidal rage in Mr. Baker."
Shanes also said Baker clearly was suffering from "psychological issues."
"This is a sad and tragic case of violence and disruption," Shanes said. "The court finds Mr. Baker had his share of mental health issues, but that alone doesn't render him insane."