Blog Post

Mary Jane Theis was born in Chicago on February 27, 1949, where she grew up. She graduated from Loyola University in 1971 and pursued a law degree from the University of San Francisco.   She returned to Chicago and served as an assistant Cook County public defender until 1983. She became a judge on July 1, 1983, a Cook County associate judge. In 1988, she won election as a circuit judge. In 1993, was assigned to the First District Appellate Court which she was elected to in 1994 and served in that position for seventeen years. She married John T. Theis, whom she went to law school with, and the couple have two children together. Theis was appointed to the Illinois Supreme Court in 2010 and in 2012 won a full ten-year Supreme Court term, after winning an election. Theis has served as Supreme Court liaison to the Illinois Judicial College. She has been a member of the Board of Governors of the Illinois State Bar Association and the Board of Managers of the Chicago Bar Association and is a member of the Women’s Bar Association of Illinois. Theis has taught at numerous judicial education programs, seminars and conferences. Justice Theis is the recipient of the American Constitution Society Legal Legend honor from the Chicago Lawyer Chapter. Theis served as Chief Justice of the Illinois Supreme Court from 2022-2025. Theis announced her retirement from the Illinois Supreme Court effective January 29, 2026.

Justice Mary Jane Theis: An Oral History