Lean says "Jeff" completely different to when she says it in Saw 3. When the door finally closes, she screams "Jeff!" for ages. Once Jigsaw's throat is cut in Saw 3, she stops. [I cannot understand what this mistake is suggesting. At no point in either movie does Lynn scream "Jeff!" for ages. She only says is a few times in both films, and for the most part, it matches from "Saw III" to "Saw IV". The only changes being out of necessity because we have to watch the finale's of both films at the same time, so we don't see everything from "Saw III."]

In the investigation of the "spike trap" scene, the rod (and the shadow of the rod) can already be seen through the left side of the crime scene photographer's neck before it even enters. [I have watched the scene several times, and even gone through it frame-by-frame, and I can guarantee that at no point do you ever see the rod (or shadow) coming out of the photographer's neck before the rod enters. In fact, going frame-by-frame, you can tell that it perfectly comes out in sync with it's entrence.]

*Spolier* When it is revealed that the events of "Saw III" and "IV" are running concurently, we are shown that the climaxes of both films supposedly occur simultaneously in under four minutes (as evidenced by the countdown clock that Rigg sees). However, if you re-watch "Saw III", you will see that the climax of that film takes about 10 minutes to transpire. In other words, it would be impossible for everything we see at the end of "IV" to actually happen as depicted, because there is too little time. (You can also tell that they edited parts of the dialogue and sound effects when Strahm is listening to make it seem faster.) [The sequence isn't in real time. It's simply meant to demonstrate that Agent Strahm is about to enter into the fray.]

When Hoffman grabs the tape (from Jigsaw's stomach) off of the tray in the beginning before he plays it, at first the tray is dirty in the wideshot, then perfectly clean and shiny in the overhead closeup, then once again dirty when the shot cuts back. [No, the tray is not dirty: it's just the light reflecting off the tray.]

John Kramer records his voice in order to test Cecil. This doesn't make sense: the tape player never is used because John talks face to face with Cecil about his game and the knives trap. [It makes perfect sense. He was going to use a recording and avoid face-to-face contact (thus preventing the possibility of Cecil identifying him later), but Cecil woke up before Jigsaw expected, probably due to Jigsaws inexperience in sedating others. Jigsaw then chose to go on with the test anyway, and simply explained the rules in person instead.] Corrected by Twotall

When Eric Matthews is standing, just before he dies, look at his mangled leg with the leg brace. As Eric wiggles, you can see the skin of his real leg, perfectly healthy, underneath. [This is not a mistake. Only his ankle was damaged (when he purposely broke it), not his entire leg. So, seeing healthy skin on his leg does not constitute a mistake.]

The reading of the 'stomach tape' after the autopsy changes considerably between the first scene of the movie and the last. [That's because the tape is longer than the first scene led on. If the entire tape was played at the very beginning, it would have given away one of the film's twists.]

During the autopsy of Jigsaw his brain is put on a scale. However when it is removed the dial on the scale doesn't move. [Some scales in morgues have to be reset manually. This is to allow time for more careful note taking, and to make sure that the M.E. remembers to record the weight. The only reason I know this is that my sister is a medical examiner.] Corrected by wizard_of_gore

The trap is set up for Riggs to open the door and kill Matthews, but Artie comes through the door first with the trap already set up, so shouldn't Artie have killed Matthews when he came through the door first? [This is incorrect because when you see Artie come in the door first he then presses the lever down locking the door and THEN putting the trap into action. So that the next person who opens the door will spring the trap.]

In the opening "Blind and Mute" trap, when the machine in the middle starts to pull at them both, the mute's chain is pulled taunt and causes him to pull back at it. After he notices the key on the back of the blind man's neck, he suddenly has plenty of slack on his chain to go all the way to the side of the machine and battle the blind man. [His distance from the machine changes. As he goes nearer the chain gets slack.] Corrected by Duff "King Of Beers" Mckagan

In the scene when Cecil is trying to get into the clinic and fakes that he left his coat, Jill turns around and unlocks the door to the waiting room, grabs the coat, and hands it to Cecil, who then charges into the room and demands the keys from Jill. Why would he need the keys if Jill never relocked the door? He was watching her the whole time, so he would have known. [He wants the keys to the medicine cabinet. They probably have methadone, among other things.] Corrected by wizard_of_gore

The two ice-blocks that are suspended from the ceiling (that kill Mathews) were present the entire film. However, it is impossible that nobody would have noticed them, as they would be melting at least lightly, causing water to drip down and make noise. Also, they are rigged to a series of wires and pulleys that would have literally been impossible not to notice. [Who's to say what a person would, or would not notice under extreme stress? The lawyer was concentrating on watching the monitors, and saving his own skin, and the detective standing on the ice block has been in captivity for six months, and wants to die, so he certainly may not have noticed some water dripping from the ceiling.] Corrected by wizard_of_gore