An Illinois woman has pleaded guilty but mentally ill in the 2020 stabbing deaths of her boyfriend’s parents.

Arin M. Fox, 42, pleaded guilty last week in McHenry County to one count of murder in exchange for prosecutors dismissing three additional murder counts and charges of possession of a stolen vehicle, aggravated battery and domestic battery, The Daily Herald of Arlington Heights reported.

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Authorities allege that Fox stabbed Noreen S. Gilard, 69, and Leonard J. Gilard, 73, to death in November 2020 inside their Algonquin home. They were the parents of her boyfriend at the time. She then drove their car to Douglas County, Colorado, where she was arrested.

An Illinois woman has pleaded guilty but mentally ill to the double homicide of her then-boyfriend’s parents.

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A stipulation signed by Fox says all parties agree that Fox, also of Algonquin, had been diagnosed with bipolar disorder, schizoaffective disorder and schizophrenia by three doctors. That document quotes a clinical psychologist as saying Fox “meets the criteria for a plea of guilty but mentally ill.”

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In a legal context, guilty but mentally ill means a defendant has mental illness but understands the difference between right and wrong,

Fox, who remains in custody at the McHenry County jail, faces 40 to 60 years in prison. Her sentencing is scheduled for Dec. 6.

Fox’s attorney, assistant McHenry County public defender Kyle Kunz, said Wednesday he had no comment on his client’s plea.