Continuity mistake: When John Gacy hands a joint to the young guy he's picked up on the corner, the joint is nearly finished. When the young guy hands it back, it's almost a full joint.
Gacy (2003)
1 continuity mistake - chronological order
Directed by: Clive Saunders
Starring: Adam Baldwin, Mark Holton, Charlie Weber, Tom Waldman
Factual error: The movie takes place in Des Plaines, Illinois, with a couple of scenes from downtown Chicago. However, throughout the movie you can see both palm trees and mountains in the background, none of which actually exist in Illinois. The producers also point this out on the DVD commentary.
Kara Gacy: God only knows what you're doing in there.
John Wayne Gacy, Jr.: What I am doing in that garage is all business related.