Barrington man pleads not guilty to killing doctor, mother of his child

A Barrington man charged with first-degree murder in the slaying of his estranged girlfriend pleaded not guilty Thursday in Cook County court, his defense attorney said.

William R. Zientek, 46, is accused of fatally shooting Vernon Hills doctor Olga Duchon on Nov. 17, 2024. The two were parents of a 3-year-old child, authorities said.

Zientek had invited Duchon, an endocrinologist, to his home for a discussion amid friction over care of the child, but the meeting turned violent.

He beat Duchon with a baseball bat, fracturing her skull, then shot her, Cook County Assistant State’s Attorney Robert Mack said at a December hearing.

Zientek told police that he fired in self-defense.

The couple’s relationship ended in 2021 after Duchon objected to Zientek purchasing and keeping firearms in their home, Mack said. She later obtained an order of protection against him.

Zientek’s attorney, Thomas Glasgow, said his client filed a report with Barrington police before the shooting claiming the former couple’s child was being molested by a relative.

Glasglow also stated that Duchon came to Zientek’s house to see the child and while there he informed her of intending to file a petition to obtain custody.

Daily Herald staff reporter Barbara Vitello contributed to this report.