The son of a circuit court judge, Fitzgerald began his own career in the law as a prosecutor in the Cook County State's Attorney's Office. When first elected to the bench in 1976, he was the youngest Cook County judge. He served as a trial judge in the Criminal Court from 1976 to 1987, when he was assigned Supervising Judge of Traffic Court. In 1989, he returned to the Criminal Division as Presiding judge. He was also appointed to serve as presiding judge of Illinois's first statewide Grand Jury. He was elected to the Supreme Court of Illinois for the First District in 2000.