Factual error: In the scene where Roxie is placed in the "paddy wagon" to be taken to Cook County Jail, the prosecutor refers to himself as District Attorney Harrison. However, the court system in Illinois doesn't have district attorneys; rather, they have state's attorneys. The original play by Maureen Watkins correctly calls him a state's attorney.
Factual error: When Mr. Flynn is in the restaurant talking about the latest socialite arrested for triple homicide, he briefly uses a telephone their waiter provides. According to an antique phone collector's association, there are many errors between the phone and the time period. First of all, that phone's design was from the Bell Tel. Co., and wasn't manufactured until about 1930. Secondly, even if the movie was set in late 1929, the phone has a handset didn't exist until 1937. Thirdly, the phone is brass-plated with an ivory handset; This colour combo was called the "Imperial", and was introduced to celebrate the 75th Anniversary of Bell Tel. Co. in 1951, and was certainly not available in the 20s.