When Bergman goes to Wigand's house for the first time, he covers his head from the rain with a newspaper running a story on the conclusion of the O.J. Simpson murder trial (The headline is "Simpson Freed"). The OJ trial only started in November 1994 - long after Wigand was fired in March 1993.
When he first calls Jeffrey Wigand, Lowell Bergman leaves a message asking Wigand to call him on 510-555-0199, a California area code, despite being in NY. Later, he leaves a similar message, saying 212-555-0199-this time using the correct area code for NY city. Although he appears to be working from home, and could therefore have the same number wired into his home and office, he would still need to live in the same area code's catchment area.
After the alleged intruder incident, when Wigand is questioned about possessing firearms, he mentions a .38 revolver, a..22 target pistol, but not the .357 magnum revolver he is shown removing from his gun safe and taking into his garden to investigate.
When Bergman first calls Scruggs (as he's flying his Lear jet), Scruggs calls in to air traffic control saying he's "Lear November 643", yet the external shot of the jet shows the registration number to be N[ovember] 6100". Then shortly after returning Bergman's call Scruggs walks out to the runway and the jet now has a registration number of "N550M".
When Bergman and Wigand first meet in the hotel, Bergman places two documents on the table for him to read; the thinner document being placed on top of the thicker one. When Wigand picks them up the thicker document is on top.
When Lowell Bergman, Mike Wallace, Dr. Wigand and his wife are at dinner just before the interview, Dr. Wigand's wife holds a menu upright close to her body. The position of her hands on the top of the menu changes directions between the long shots and the close-ups.
When Richard Scruggs is shown flying his Learjet, he gives the plane's tail number as "November six four three." Right after that, though, we see an exterior shot of an aircraft with the tail number N6100. Later, Scruggs, Motley, and Mississippi Attorney General Moore are seen at an airfield walking toward a Learjet with the tail number N550M.
CBS building in New York, which is at 51 West 52 Street, corner of 6th Avenue - when Bergman looks out of the window, Central Park is to the side of the office, making the building on Madison Avenue or even east of that; if he was on 6th Avenue the park would be straight ahead.
Wigand stands in the hallway at his school in Kentucky as he talks on a pay phone to Scruggs, who is in his office in Louisiana. Although Louisiana is west of Kentucky, via the window at Scruggs's office, we see the sun has set, yet the hallway at the school is filled with light, indicating the sun is still shining.
When Wigand is in the Seelbach Hotel on the phone with Bergman, Wigand says that he "can see them (Brown & Williamson) across the street." This would have been impossible since the (now former) B&W Tower is located one block north of the hotel (the building across the street from the Seelbach is the National City building).
When Wigand is returning from Mississippi, his car is shown passing a highway sign saying "Louisville" via Indiana state highway 31, which runs through southern Indiana. Since Louisville's airport is not in Indiana, there would be no reason for Wigand to be southbound in Indiana heading for Kentucky.
In the beginning of the film when Mike Wallace refuses to move his chair away from the Sheik, the translator translates Mike's English into Farsi to the Arabic-speaking Hezbollah. Farsi and Arabic are not the same language and usually Persians and Arabs do not understand each others' languages, unless they studied it.
The film concludes with the statement that Jeffery Wigand's harassers were never found. In fact the FBI investigated thoroughly and concluded that Wigand had faked the alleged death threats himself. This was mainly due to interviews with Mrs. Wigand who also believed the threats were faked.
On three separate occasions the same Yellow Taxi is occupied by Bergman or greeted by Bergman when he met Charlie from the Wall Street Journal, the numbers on the roof and door are the "1T80". The odds of this happening are slight, since there are 11,787 Yellow cabs in New York.