Other mistake: In Saw II, Jigsaw shares a story with Detective Matthews about how he attempted suicide after his cancer diagnosis by driving his car off a cliff. We then see Jigsaw pulling a metal rod out of the left side of his stomach. However, no puncture wound/scarring is visible on Jigsaw's stomach when his autopsy is being performed. (00:00:50)
Saw IV (2007)
Trailers
Directed by: Darren Lynn Bousman
Starring: Tobin Bell, Betsy Russell, Costas Mandylor, Scott Gordon-Patterson, Scott Patterson
More trailers
More mistakes in Saw IV
Eric Mathews: I don't want to play anymore.
Trivia: When Officer Rigg is walking through the school, before he finds Morgan and Rex in the rod trap, he walks by a dark room blocked off with police-barrier-tape. Originally, there was a scene that revealed this was the room where Troy from "Saw III" died, but it was cut, presumably for pacing reasons.
Question: A glass casket with a key inside it is shown in John's warehouse. What does that mean?
Answer: This was revealed by director Darren Bousman to have originally been used in a now-deleted (and not released as of Oct. 2020) scene in the movie. The glass box is used for what is (most likely) a different purpose in Saw V.
Answer: It plays an important role in the next few movies.