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.
Continuity mistake: When Velma is dancing and singing for Roxie after making her the offer to replace her sister, during the first half she has an obvious run in her right stocking and a hole about the size of a quarter over her knee. When she tells Roxie the second half is better and finishes her number, the run has disappeared.
Continuity mistake: After Roxie shoots Fred Casely, a photographer takes a picture of the body and in the flash from the camera, you can see Fred's eyes are closed and his head is facing straight up. After Roxie's 'Funny Honey' number, the attorney interrogates her and uncovers the body for a neighbor to identify it. When he does this, you can see that Fred's eyes are open and his head is tilted to the side.
Continuity mistake: During the Cell Block Tango, 'Pop' dances with her partner while she sings. When she says "not chewing, popping!", she turns her head sharply and some of her hair lands on her partners hat. When she says, "You pop that gum," she moves and the hair falls off, but in the close up, it is on his hat again in the same position.
Continuity mistake: Near the end of the movie, after Roxie's audition, Velma is pitching her act again when Roxie puts on her coat and buttons it. The camera cuts back to Velma for a minute, then when it cuts back to Roxie her coat is unbuttoned, then seconds later she is walking through a door and her coat is buttoned again.