Factual error: Several mistakes about the clock in Jigsaw's workshop: around 300 years ago the first pendulum clocks were built. They were completely different by size and design than this one, so the claim that it is so old is completely wrong. Real pendulum clocks like the one seen in the movie never have a second hand from center. You can also see by the movement of the second hand that it is a modern, battery operated quartz movement. This also means that the ticking you hear is not created by the clock itself but was added later.

Visible crew/equipment: Several times in the movie you can see a stunt double for Donnie Wahlberg, like when he tries to hang himself. Art runs over and there is a wide shot focusing on both of them. No slo-mo required, but you can see it's a stunt double.

Continuity: 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.

Continuity: When Agent Hoffman writes the letter to Amanda, he puts the envelope so her name is pointing down, yet when Amanda opens the drawer her name is at the top. The director had to do this or it would have revealed Hoffman was the new apprentice all along.

Continuity: When Agent Strahm has finally realised where the final game is being played, he holds up the piece of paper of Jigsaw and Art outside the Gideon building. There is a hand at the top of the picture, which is a newspaper clipping, but he is holding a picture, not a newspaper. This is a reused shot of when he shows Agent Perez the picture earlier in the movie.

Revealing: When Art is hitting the Trevor (the blinded man) character with the hammer/hatchet in the beginning, if you look closely, you can see blood coming from Trevor's head, yet there is no wound or cut. The blood is actually coming from the prop that is hitting him in the head.

Revealing: When Cecil's face is being cut by the Knife-chair, the first time he comes into the blades, it is painfully obvious that the blood is being pumped through the knives, and that his face is not being cut. You can even see his bloody, yet cut-free, face almost come through the knives for at least two full seconds, before there is a flash-frame jump-cut, and a number of deep cuts magically appear on his face.

Continuity: If you go back and compare the ending of "Saw III" with the ending of "Saw IV", you can tell the lighting is different in certain areas (specifically when Strahm sees the dooor swing shut on its own), even though it is supposed to be in the same time and place.

Continuity: When Rig opens the door the clock says 00:00 time left, but when he is talking to Art on the floor the clock says 00:01.

Visible crew/equipment: As Jill is being interrogated, when it cuts to a shot where the two cops are looking at her through two way glass, a camera man is visible between them and the boom mic in seen at the top left hand corner, very faintly.

Continuity: The timer for Ivan's trap is messed up. The first shot we see it at 3 seconds. 12 seconds later we see the time at 42 seconds, and we know the 12 seconds are continuous as Jigsaw's tape plays during this time. 23 continuous seconds later we see it at 37 seconds (this would have been right if not for the second shot). This is when Jigsaw's instructions stop and his one minute should begin. As the first scythe descends into his right eye the timer is at 55 seconds. We see it at 57 seconds just before he gets his limbs ripped off. Two seconds is not enough time for him to scream after the injury to his right eye and recover to convince himself to take out the left so it must be a 1 minute 2 second interval, meaning he had at least 83 seconds to complete the task rather than 60 stated in the tape.

Continuity: *SPOILER* When Agent Strahm breaks into the Jigsaw's room in the end, he literally comes in less than a minute after "Saw III"'s conclusion. Yet, if you look, Amanda's dead body is in a completely different position than the end of "Saw III", which makes no sense, as there was no time or reason for it to be moved. At the end of III, her body was facing towards Jigsaw, and there was only a small amount of blood around her. Here, her body is facing in a different direction, and there is a ridiculously larger amount of blood.

Continuity: When Riggs arrives at the shop, the clock shows 1:16. But, at a second look, it's 3:46.