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Justice Obrien for Illinois Supreme Court

Justice Mary Kay O'Brien



Mary Kay O’Brien is an experienced and highly qualified judge with deep roots in the community and a long history of public service.

Justice O’Brien has served on the 3rd District Appellate Court for nearly 18 years. She has heard more than 4,500 cases and served on numerous committees, including the Supreme Court Rules, Legislative, and Appellate Court Access to Justice Committees, the Illinois Courts Commission, and the Lawyers Assistance Program, among others.

Prior to becoming a judge, O’Brien served as a state legislator from 1996-2003. Despite facing an incumbent, O’Brien ran to fight for working families and commonsense values. Her victory secured the Democratic majority in the House of Representatives. While serving in the General Assembly, O’Brien chaired the Judiciary Committee on Criminal Law where she presided over death penalty reform and fought to protect children from violent offenders and expand the statute of limitations for sexual assault against minors.

A proven vote-getter with a history of winning tough battles, O’Brien was elected four times by the voters of the 75th District, won a decisive victory for the 3rd District Appellate Court in 2004, and was retained in 2014 by nearly 80% of voters. Her political skills were developed at a young age while campaigning for her family friend and political mentor, State Senator Jerome Joyce.

O’Brien was raised on the family farm in Reddick, Illinois where she learned the importance of hard work, integrity, and public service from her parents, Norma and Don O’Brien, a retired Local 265 sheet metal worker.

 Justice O’Brien attended Joliet Junior College, Western Illinois University, and the University of Illinois, where she earned her law degree. In addition to her service as a legislator and judge, O’Brien worked for former Attorney Generals Neil Hartigan and Roland Burris for four years where she focused on consumer advocacy, including working to stop a crop insurance scam affecting Illinois farmers. She also worked in the Grundy County State’s Attorney’s Office and in private practice covering family law, criminal law, real estate, banking, and municipal law.

She and her husband Todd Gereaux are the proud parents of Mason, Mike, and Matt. O’Brien is an active member of numerous bar associations and local organizations, including the Town and Country 4-H Club, Lion’s Club, the Kankakee County NAACP, and AMITA St. Mary’s Hospital, where she currently serves as board chair. She is also a longtime leader for the Illinois Lawyers Assistance Program (LAP), a non-profit organization that protects clients and the public from impaired lawyers and judges by providing mental and physical health services to legal professionals in need.

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