The real Jeffrey Wigand asked for two concessions from the filmmakers: that they change the names of his daughters, and that there be no smoking anywhere in the film. Both requests were granted (except for the three small instances previously mentioned).
The scenes at the Pascagoula mansion, on the Gulf of Mexico, were filmed at the home of the real Richard Scruggs (the attorney portrayed in the film) in Pascagoula. Hurricane Katrina destroyed the home in 2005.
Jeffrey Wigand, the anti-smoking subject of this movie, requested a ban on cigarettes in the film. However, cigarettes are smoked in the movie at least thrice: (1) by a woman in the background as Wigand enters the airport, shortly before served with a restraining order, (2) by a Muslim soldier seen briefly while Bergman is being transported to the Hezbollah meeting site, and (3) by a photographer with whom Bergman converses briefly about what might be going on inside the courtroom.
Toward the end of the film, Mike Wallace shows Lowell Bergman an unflattering article and editorial about CBS in the latest New York Times. The article and editorial are clearly from different sections of the paper. This would seem to be a goof, since the Times' op-ed pieces usually appear in the back of the main news section. The real-life pieces to which this scene refers, however, were published on a Sunday (12 November 1995), which means that the news and editorials would in fact have appeared in separate sections, just one more example of director Michael Mann's eye for detail.
In a scene in Bergman's office, Mike Wallace tells Lowell Bergman, "I don't plan to spend the end of my days wandering in the wilderness of National Public Radio." In reality, Bergman left CBS in 1998 (not right after the Jeffrey Wigand piece, as depicted in the movie) to work for Public Television.
Wigand tells his entering chemistry class that their very first experiment would be to "measure the molecular weight of butane." Student comprehension of a topic as complex as this would require background knowledge of chemistry. But by failing to raise their hands to indicate they had such knowledge, the students would likely not have been able to understand this as their first lesson in the subject.