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)
1 other mistake
Directed by: Darren Lynn Bousman
Starring: Tobin Bell, Betsy Russell, Costas Mandylor, Scott Gordon-Patterson, Scott Patterson
Continuity mistake: The blood stain on Riggs' white shirt around the neck has blood under the collar, then at the end it is over the collar and has increased in amount.
Eric Mathews: I don't want to play anymore.
More trivia for Saw IV
Question: A tape recorded by John directed toward agent Perez states that her partner would soon take the life of an innocent man. How did John know that agent Strahm would kill Jeff? For all he knows, Strahm could have followed Rigg through the factory rather than Jeff. The "if you're good at anticipating the human mind, it leaves nothing to chance" excuse doesn't work here. The only reason Strahm followed Jeff was because he heard Jeff hit a ceiling light with a crowbar.
Answer: Realistically there is no way he could have known. The writers were just working backwards from the plot point on this one.
Phaneron ★