Other mistake: After Jeff gets the key from the Rack trap room, the shotgun fires and hits the judge. He is standing with the shotgun to his right, yet he is hit on the left side of his face. There is also an inconsistency with the timing. The gun fires, then the actor turns to reveal the wound on the left side of his face. It's easier (but in no way required) to see the glaring mistake with slow motion.
Other mistake: Near the end of the film when Jigsaw has the tape player, the 'play' button is near the left side. But Jigsaw's finger is on the right side, not even close to the play button. Jigsaw presses on the right side where there isn't even a button, but the tape begins to play anyway although nobody pressed the actual play button.
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