Carl Chatman, 58, had been serving a 30-year prison sentence. A judge ordered his immediate release after prosecutors moved to dismiss the charges in the 2002 sexual assault, the Chicago Tribune reported.
Another man was released after prosecutors dismissed a murder charge dating from 1990. Lathierial Boyd, who was serving an 82-year sentence, was convicted based on the testimony of a man who was wounded in the shooting outside a bar even though witnesses said he was at his sister's at the time.
Sally Daly, a spokeswoman for Cook County State's Attorney Anita Alvarez, said a lengthy reinvestigation of the charges against Chatman preceded Tuesday's hearing.
Chatman, who has been diagnosed with schizophrenia, was homeless when he was arrested and charged with sexually assaulting an employee at the Richard J. Daley Center, which houses courts and other government offices. Police had little evidence beyond the woman's story with no one else reporting having seen Chatman in the building at a time when he allegedly spent the night there.
Chatman's lawyer, Russell Ainsworth, found the same woman accused a Polish janitor of sexual assault in 1979 in an office building where she worked at the time. Ainsworth said her story was almost identical in both cases and accused her of fabricating them to give her grounds for lawsuits.
Edward Szymczak, the janitor, fled to Poland. He wrote the judge in his case saying he was only doing so because he did not have the money for an effective defense against a crime he did not commit.
The woman's husband told the Tribune the decision to drop charges against Chatman is "infuriating." The newspaper withheld his identity to protect his wife's.
"To let this man go is wrong. He was convicted and he deserves to be in prison," he said.