How Accurate?

Except for the two-part pilot episode and the Season 4 episode "Cooker in the Sky", which was based on an actual case of the real Untouchables, all of the episodes came from the imaginations of the show's writers. Many episodes included real historical characters and a few included real historical events but for the most part the show was fiction. For instance, the real life Eliot Ness never did battle against the likes of New York mobsters Dutch Schultz, Legs Diamond, and Waxey Gordon like he did on the series and the real life Frank Nitti committed suicide instead of dying in a blazing gun battle with law enforcement officers.

In some of the later episodes, Desilu added the disclamer graphic "The Untouchables is based on the book by Eliot Ness and Oscar Fraley. Certain portions have been fictionalized". In still later shows, it was shown as a graphic and voiced by Les Lampson (the KTTV weekend news anchor and "voice" of the Untouchables intro). Many episodes had NO basis in fact. Obviously, Ness, Capone, Nitti, Bugs Moran, Jake Guzik, Ma Barker, and a few others were real gangsters in their day, but were heavily modified characters for the show. Quinn Martin had a few favorite actors that showed up in later QM Productions like "The FBI".

"Last of the Untouchables" which details the life of former Untouchable Paul Robsky (on whom the character of Jack Rossman in the series was based) should be taken with a grain of salt. Robsky was a very disgruntled and jealous individual who hated the fact that his former boss, Eliot Ness, had become a crimefighting legend while he was all but forgotten in the annals of history. He never missed the chance to run down and belittle Ness and his accomplishments. I'm not saying that everything in Robsky's book was untrue just that you ought to consider the source and where it's coming from.

After a lot of reading on Ness, I found out that maybe he wasn’t such a big shot. But these forums deal with the series, and no matter how inaccurate or fictional, Robert Stack was just excellent in that role

Horror, Science Fiction & Fantasy

The Ma Barker episode is cringe worthy. The birthday party for her son was unintentionally funny particular the shot of her handing a jumper she knitted.

If you don't mind a comment by someone who is really late to the party, here goes: I was a tv film editor in the early 1970's and our local station ran these episodes. We ran each and every print to assure continuity and also to identify scenes that could be eliminated for time as each episode was shortened by 3 minutes for commercial purposes. Eventually we editors would notice countless goofs, anachronisms and errors. In one episode, a conversation takes place in a prison theater projection room. The equipment is obviously modern (for 1960) and not the period stuff a 1930's prison would have. My favorite however is a car chase where a vintage automobile crashes. The story called for the car to overturn but the producers were clearly not about to wreck a valuable antique. Instead, a stock shot of a 1950 Ford, swiped from the movie "Thunder Road" is used. I remember how the editors gathered around the projector, running the scene again and again and laughing at the miraculous transformation of a 1930 vehicle into a 1950 sedan. All I can say is that if such outrageous errors were ignored, how accurate would the story lines be? Turning out an episode a week at minimum cost required a lot of concessions to the truth. And when a single man is to be credited with arresting almost every mob guy from the 1930's, the results are breathtakingly untruthful. They might as well have created a totally fictional policeman in the manner of "Law and Order". Or made him a superhero!

[deleted]

The original book was a novel. Ness originally wanted it to be accurate, but Oscar Fraley insisted that it be heavily fictionalized in order to have sales appeal.

As for the TV series, at the end of the pilot episode the credits say that the series is based on the novel "The Untouchables". At the end of other episodes the credits say that "The incidents portrayed in this episode are fictional . . . ."

So the series is clearly fictional, and a lot of dramatic license was used to get better ratings. Based on what I know, I'd say it is about 95% fiction, with a few facts sprinkled in from time to time.