Judge Joan Margaret O'Brien: Professional Background and Legal Expertise

Hon. Joan Margaret O’Brien is a judge for the Cook County Circuit Court in Illinois. She was elected to the Circuit Court in 2000 and was retained in subsequent elections.

While on the bench, O’Brien has held assignments in the Fifth Municipal District and the Child Protection Division. In addition, she served as a supervising judge of the felony courts for the Fifth Municipal District and is also credited with establishing both the Veterans and Drug Treatment Courts in Bridgeview.

She completed a J.D. at Drake University Law School in 1982.

After law school, O’Brien joined the Cook County State’s Attorney’s Office, where she served as a career prosecutor until joining the judiciary in 2000. Over the course of her tenure there, she first worked as an assistant state’s attorney assigned to felony narcotics, traffic, and misdemeanor cases while also prosecuting criminal appeals. She then prosecuted cases in the felony trial division for three years (1989 to 1992). As she rose through the ranks, O’Brien later served as a deputy supervisor for felony review and a supervisor of the First Municipal District (1993 to 1996) before being named chief of the Municipal District, where she was tasked with supervising 150 fellow prosecutors.