Factual error: In the scene on the El where the cop gets shot, you can hear the train engineer saying, "Balbo, next stop"; this is also said later on the police radios, when they say there is an officer down at the Balbo station. Two problems: 1) There is no Balbo station. 2) Even if there were, the station they start from is at Lake street (looks like the main transfer station at Clark and Lake), and the train pulls out going north. However, Balbo is south of Lake street.
Factual error: When Dr. Nichols leaves the damaged elevator, and Kimble later exits (the infamous arm in the door shot), neither would be possible as the elevator was emergency stopped by Nichols and can be seen positioned just below the floor. The elevator doors would not line up with the floor doors, and both sets would need to be manually opened.
Factual error: When Kimble is being interviewed by the police, a cop says "book him." We later learn the police were still trying to find out if a one armed man could've done it. The police can't arrest someone if the investigation is still ongoing. An arrest is supposed to mark the end of an investigation, the trial is the next stage.
Factual error: In the train crash scene there are many mistakes. 2 locos are pulling a hand full of cars, a small switcher loco would actually have been used. Oil journal bearings that haven't been used for decades. A flat car carrying logs, but there is no logging in the Chicagoland area. The second loco for some reason derails. In reality the train would have just pushed the bus a few hundred feet with no derailment. The shed explodes. The 200 ton loco just slides along the soft ground.