• Continuity

    (at around 1h 50 mins) When Colin uses Queenan's phone and redials the last number (Billy's), Queenan's phone displays the called number as 617-869-1469. When Billy calls back from that same phone a couple of minutes later, the calling number shows as 617-177-9528, which doesn't match.

  • Continuity

    Near the end of the film, after Costigan is shot, the elevator is blocked. It tries to close but, Costigan's body is blocking it. After Brown is shot, the elevator doesn't move at all.

  • Continuity

    When Queenan is thrown off 344 Washington St., a lot of bright red blood is splattered upward, then his body hits the ground. A shot of Queenan's body on the grounds shows a little dark red blood.

  • Continuity

    When Costigan is shot in the elevator, the pattern of the blood on the elevator's inside wall is different between shots. In the next shot, the blood on the wall is dry.

  • Continuity

    (at around 2h) When Frank is running away during the shootout, he gets shot on the left side of his body, and blood hits the wall. In the next shot, you can clearly see him running and no blood nor bullet holes in his shirt or jacket. When he sees Colin, he is taking off his jacket and his bullet wound has switched to the right side of his body.

  • Continuity

    (at around 2h 15 mins) When Costigan is shot in the elevator, there is no blood on Sullivan's face. When the camera cuts to him again, his face is covered in blood.

  • Continuity

    (at around 2h 5 mins) When Costigan is discovering the envelope on Colin's desk, the markings on the envelope change at least twice in between shots.

  • Continuity

    (at around 2h 10 mins) Between the discovery by Costigan of the envelope on Colin's desk, and the return of Colin in the room, the arrangement of the various piles of documents on the desk have changed.

  • Continuity

    (at around 1h 50 mins) When Delahunt calls Costigan over as he is dying, Costigan prepares to sit next to him in one shot. After a close-up of Delahunt, Costigan prepares to sit next to him again.

  • Continuity

    After Queenan dies, and Sullivan picks up his phone, the number Sullivan dials for Costigan isn't the same one seen when Costigan calls back, even though it's the same mobile. When Sullivan calls, the number begins with something like "617-854" and when he sees Costigan calling back, it's "617-177".

  • Continuity

    Before French dies, he starts to cough, and the windshield has fewer bullet holes than in the previous shot.

  • Continuity

    When Costello lies dead in the shovel of the excavator, his right arm moves between shots.

  • Continuity

    In the final scene of the movie, when Sullivan is walking down the hallway and into his apartment, his belt is light brown. When he's dead on the floor, it's very dark brown, almost black.

  • Crew or equipment visible

    When Mr. French backs up the car, just before he is shot, the driver has no beard. It's clearly a stuntman.

  • Crew or equipment visible

    When Costigan attempts to arrest Sullivan on the roof, some rigging appears in the sky.

  • Crew or equipment visible

    After Queenan is thrown from the roof, the next shot is from Costigan's point of view. When Costigan moves his head slightly to the right, the dolly track appears briefly.

  • Factual errors

    (at around 2h 10 mins) It would actually be nearly impossible for Sullivan to completely delete the records that prove that Billy is an undercover cop. It was shown that those records were stored on some part of the department's primary database/records system (as opposed to being simply a file on Queenan's PC, for example). Such critical systems are ALWAYS backed up and historical copies kept under very secure conditions, in order to keep exactly that type of deletion from occurring. All anybody would have to do to prove that Billy was working undercover is to retrieve a backup copy of the information. If Sullivan wanted to truly delete all records of Billy's work, he would actually need to delete the current records (as shown) AND delete each of the historical backups kept in storage.

  • Factual errors

    (at around 1h 50 mins) When Sullivan uses Queenan's phone to call Billy, he leaves a blood smear on the dial-pad. In the time between Queenan's death and the call being placed, the blood on the outside of the phone would have dried; Sullivan wouldn't have gotten blood from the phone on his hand, and wouldn't have left a smear.

  • Factual errors

    (at around 2h 20 mins) At Costigan's funeral, bagpipers are heard playing part of the second movement of Antonín Dvorák's "Symphony No.9 in E minor." In the credits it is incorrectly listed as "Symphony No.5 in E minor."

  • Plot holes

    In the elevator shoot-out near the end, Colin shoots the 'other rat' then cleans the gun of finger prints and residue and leaves it carefully on the floor. The forensics's people will have examined every gun and bullet fired and found this discrepancy.

  • Revealing mistakes

    (at around 2h 15 mins) When Costigan is in the elevator after he arrested and handcuffed Sullivan, Costigan slams against the wall with Sullivan. Sullivan's left hand is supposed to be handcuffed behind his back, but he puts out his hand to catch himself as he hits the wall.

  • Revealing mistakes

    When Queenan's body is coming down from being thrown from the roof, Costigan looks up before Queenan's body is in plain sight.

  • Revealing mistakes

    The counterfeit State Police patches on the uniforms and logos and computer desktops are completely different from the authentic ones on the documentation in the evidence box for Queenan's murder and on the cruisers deployed for the arrest.

  • Revealing mistakes

    (at around 2h 20 mins) After Colin is killed and the camera moves towards the window, a stunt man is clearly put in the place of where Matt Damon's body should lie for a brief moment.

  • Revealing mistakes

    After Costigan is shot and killed, and his gun is kicked from his hands, something makes the sound of a camera shutter firing. A publicity photo was probably taken while the scene being filmed.

  • Revealing mistakes

    (at around 2h) When Colin shoots Frank in the chest, killing him, the device used for mimicking a bullet wound is clearly visible under Franks gray "Irish" t-shirt.

  • Revealing mistakes

    In the last scene, when Colin is shot and falling, you can see the stub of the tube used to splatter the blood.

  • Revealing mistakes

    (at around 2h 5 mins) After Costello is shot and killed, his flip-style cell phone rings, even though it is open. In reality, there would be no ring, only a tone in the earpiece, letting the user know there is an incoming call.