Plot hole: In the end, all they have to do is ask the President, when he's conscious (Liev didn't kill him; he just knocked him unconscious), who killed everyone in the control room and nearly killed him. He would know who the traitor is and it's not Salt - when they look back at the facts, they'll see how Salt only killed when she absolutely had to, and how she saved lives and stopped a 3rd world war.
Revealing mistake: When Leo is laying his dead kids on the grass, the little girl keeps moving her eyes and breathing.
Revealing mistake: At the end when Katie enters Hunter's room and throws Kristi against the camera, Katie's reflection in the wardrobe mirror shows her in a different position from when she attacks Kristi, to after she drops out of view.
Continuity mistake: When Ariadne wakes in the Snow Fortress and the floor goes from under her, we can see her gloves fall in to the crack but in a different camera shot of her we can see the gloves are now back near her head again. (02:12:20)
Visible crew/equipment: When Hoffman runs to hide from the second coroner, he goes right up close to the camera. When he does, you can see the camera's shadow on his face. (01:08:00)
Continuity mistake: During the close up of Paul writing the word "Mark White" on the lid of the coffin, he is using his right hand. The shot then goes back to Paul, and he is writing with his left hand.
Factual error: When Ewan McGregor drives to Belmont MA to visit Paul Emmett, he checks the mailbox to see whose mail it's addressed to. It shows the name Paul Emmett, address, Belmont MA 02324, which is the wrong zip code; it is the zipcode for Bridgewater MA, and Belmont MA should be 02478.
Other mistake: In the scene where Jensen is attempting to decrypt the password on the hard drive with the algorithm, he uses the command "traceroute d-hea" which is commonly used to test network connectivity, not decrypt passwords.Then follows it with the command "dir" to reveal HTML code instead of directory structures.
Factual error: Detective Bowden's son is ejected from the front of the car and there is a hole in the front windshield. The collision was a straight side-swipe and his momentum should have taken him out the passenger-side window. He would have gone out the windshield if the car had been rear-ended or if they had crashed head-on into something, but the car came to rest in an open field.
Other mistake: Finbar is shown torturing a victim while the victim has his head in a halo used for immobilizing a person's head. The screws to hold the victim's head tight can be seen not to be touching his head, yet the victim is still bleeding from the screws.
Continuity mistake: When Ree visits a girl holding a baby, when she's about to leave the baby's hat swaps from off to on between shots.
Plot hole: When Dylan enters the vampire Vargas's bedroom to interrogate him, Dylan frequently steps away from the door to let sunlight in to burn Vargas, so that Vargas will cooperate with the interrogation. Vargas is in his bed and could easily cover himself with his sheets to block the sunlight, but never does.
Continuity mistake: First when Carson kisses Rachel she's on his left side. When the kiss is over she's suddenly on his right side. (00:52:00)
Factual error: When Luke puts the starting cables on the battery of the pick-up truck sparks fly from the connection. However since he hasn't connected the cables to anything on the other end yet no sparks should be visible. Next to that the battery is nearly dead so there is no power to give the sparks in the first place.
Audio problem: When Niko is going to get the key for somewhere for Zoe to hide and then Zoe disappears he says "Zoe"? When he says it his mouth does not move but once he finishes saying it that's when his mouth moves.
Factual error: When the Senator is looking at the rent ledger, there are entries for each property as well as the date that money was collected. One of the dates is 2/29/74, yet 1974 was not a leap year. The only leap years in that decade were 1972 and 1976. (00:56:30)
Continuity mistake: When the two young lads jump off the bridge to escape in handcuffs, as they fall together the handcuffs disappear. (01:12:00 - 01:13:00)
Continuity mistake: Jason spits blood onto Joker's chin which changes spot wise and shape wise by the next shot.