
Continuity mistake: During the scene where Ness kills the Italian mobster in the lodge near the border, the moment he shoots him the wooden rail behind has two sticks underneath, half a second later, when the mobster is flying backwards dead, the sticks disappear, and a second afterwards, when he is laying dead, the rail's appearance has nothing to do with the previous two.
Answer: It's about 50% truth and 50% fiction. Ness, Al Capone, and Frank Nitty are real, of course, but the characters played by Connery, Garcia, and Smith are fictional. Ness started out with 50 candidates for his 'Untouchables' force. This was whittled down to 15 finalists and from that he selected 9 agents (none of which has the same name as the characters played by Connery, Garcia, and Smith). It's true that Capone was convicted for tax evasion. He was sentenced to 11 years in prison, but received an early release because he was in the last stages of syphilis. He died shortly after being released from prison.
raywest ★
Capone lived for 8 years upon his release from prison. The 8 years being slightly longer than the actual prison time he served, which was just over 7 years. He died, having the mental capabilities of a 12-year-old.