After filming a scene shot at the school, Russell Crowe pranked young castmates by screaming and ripping out his hair. The realistic gray wig had many fooled and horrified, until the crew and Crowe erupted in laughter.
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.
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).
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.
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.
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.
The outside of the Pascagoula courthouse shown early in the film is not the actual location where events took place. The real courthouse in Downtown Pascagoula was being remodeled during filming and the temporary courthouse was a re-purposed old grocery store on Market Street, which has since been demolished and replaced by storage units. It's the door of the temporary courthouse shown in closeup as they are entering.
The scenes of Pascagoula Beach Blvd. show a seawall next to the road where the Gulf comes up to it. Since filming, the Army Corps of Engineers pumped sand from the sound and created a sand bar that runs the entire length of the beach-front connecting it to the "sandbox" on the east end, extending a 1/4 mile sand beach into one approximately 2 miles long. The concrete barriers along the road were replaced with a promenade between the street and the sand.