(at around 2h 5 mins) When Sullivan pulls up Costigan's record in the computer, his date of birth is initially listed as 11/7/1984. The next time he pulls up the record, the date is 11/7/1980.
(at around 2h 15 mins) When Billy is arresting Colin, he says "you didn't come here to talk, you came here to get arrested" but his mouth is not moving.
(at around 2h 5 mins) While Gwen is talking on the phone, the word "hell" is obviously dubbed over the initial word "fuck."
(at around 4 mins) In the beginning when Frank executes a kneeling man and woman, the woman falls on the back of the man. The next scene shows her clearly beside him, then the next shot, she's back on the man's back.
(at around 1h 28 mins) When Billy's phone goes off in the porn theater, it is on vibrate. However, in the alley when he is following Colin, it rings when he receives a text. The event is described in the script by William Monahan: "His phone has fucked up, as they do."
(at around 17 mins) Costello's signature on the condolence card on Mrs. Costigan's coffin clearly changes appearance between the two successive shots.
(at around 1h 14 mins) When Queenan and Dignam confront Costello it's just the three of them standing there talking. But when Costello says "I've got a date with some angels." The camera goes back to Queenan and you see a fourth person standing there (the FBI guy) whom you've never seen before in the shot.
(at around 2h 10 mins) The taped recording of Costello and Sullivan that Madolyn listens to is from their conversation in the porn theater. However Costello's lines are different on the tape than they were in the theater. One example: While in the theater he says "It won't be me who suffers for it" (at around 1h 26 mins). Whereas on the tape you hear him say "It won't be me who pays for it".
(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.
(at around 1h 50 mins) When Sullivan uses Queenan's phone, the close-up shows the blood transferring from his finger to the left side of the talk button. The wide shot shows the blood on the right side.
(at around 1h 24 mins) Sullivan and Costello meet in an adult movie theater in Boston's Chinatown. However, an earlier reference to the Patriot Act (at around 1h 2 mins) places this movie no earlier than 2001. By then, the porno houses of Boston's "Combat Zone" were nothing but a memory.
(at around 58 mins) When Costigan storms out of Madolyn's office after she refuses to prescribe sedatives, a "sigh" sound is clearly dubbed over Madolyn saying "fuck". She then sighs, and the exact same sound is heard.
(at around 4 mins) When we see Frank Costello from the back as he address young Colin in the auto shop, he has a cigarette in his mouth. In the next shot of him from the front, his cigarette is gone.
(at around 1h 50 mins) When Colin calls Costigan for the first time, he smudges blood across the call button. In the next shot, the smudge is all but gone.
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.
The rank of "staff sergeant" no longer exists in the Massachusetts State Police after the 1992 consolidation of state controlled police forces.
(at around 1h 45 mins) When Sullivan and Dignam are fighting and arguing, Captain Ellerby holds back Dignam in the first shot, but a millisecond later, he yells "SHUT UP!" in the middle of the room, yet it's impossible to move that fast.
(at around 1h 45 mins) When Queenan's body was coming down from being thrown from the roof, Costigan looked up before Queenan's body was in plain sight.
(at around 1h) When the cops are set up to conduct surveillance on the microprocessor deal, the sweat stains on Ellerby's shirt change back and forth.
(at around 2h 5 mins) Sullivan says that the highest decoration the Massachusetts State Police has is the Medal of Merit. It is actually the George Hanna Award.
(at around 2h) As Mr. French is backing up the car, and just before he gets shot, if you slow-mo the movie, you'll see that he has no beard. The driver is clearly a stuntman.
(at around 36 mins) After Costello finishes beating Costigan's broken hand on the pool table, he tosses some money down and begins to walk away. As he is walking away, Costigan is seen in the background slipping down from the edge of the table to sit on the floor and nurse his hand. When the camera angle shifts, however, Costigan is still leaning on the side of the table and slides down to the floor a second time.
(at around 2h 20 mins) None of the pipers are playing the bagpipe music "Going home" when standing at and marching off from the funeral.
(at around 1h 45 mins) When the truck is leaving the scene at 344 Washington, the left back window is shot out twice.
The processors in the movie are supposed to be made by a fictitious company called MASS Processor. However, the processors shown have the logo of the Italian chip maker giant ST Microelectronics. The goof is corrected in the DVD release.
(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.
(at around 1h 16 mins) In one scene, Queenan hands Costigan a glass of ice water, which disappears and reappears between shots.
(at around 36 mins) When Costello is hitting Costigan's arm with his shoe, he is clearly hitting the table area in front of his arm.
(at around 22 mins) Costigan is smoking in the bar when he orders a cranberry juice before meeting Mr. French. Smoking in bars is illegal in Massachusetts. However, given the number of Costello's men who drink in this bar, it may be that the bartenders are not particularly proactive about enforcing that particular law.
(at around 6 mins) When Costigan and Brown are training at the Massachusetts State Police Academy, the Throgs Neck Bridge, which connects Queens and the Bronx, is in the background. The actual Massachusetts State Police Academy is in New Braintree, a small town near Worcester, with no large suspension bridges nearby.
(at around 1h 10 mins) Madolyn's UMass diploma (visible briefly in a box of her stuff when she's moving into Sullivan's apartment) appears to be a black-and-white photocopy. Real UMass diplomas have an embossed Seal of the Commonwealth of Massachusetts in red, blue, and gold ink raised up from the paper, while Madolyn's is entirely black and looks to just be printed on the surface.
(at around 44 mins) Costigan and French get into a maroon Buick Roadmaster, where Costello is waiting. When Costigan opens the flip-phone, the dashboard in the background is that of a newer Mercedes, with a black interior.
(at around 1h 19 mins) When Costigan and Costello's men are writing down their social security and account numbers for Costello at the bar, Costigan corrects Fitzy's spelling of 'Citizens,' and the open end of the envelope is facing to their right. When Fitzy picks up the envelope, however, it switches so that the open end is facing left, then right, then left again in subsequent shots.
(at around 36 mins) When Costello gives Costigan money in the bar to have his arm checked out, he counts out three bills from the wad he's holding in his left hand and drops it on the pool table. In the next frame, the money has shifted to his right hand and there's no money on the table.
(at around 1h 30 mins) When Costello and Costigan are sitting at the table in the restaurant, discussing who the rat is, a handgun falls to the floor. Costello picks it up and points it at Costigan's face. You can hear him manually cock the hammer, but when the camera angle changes, the hammer is not cocked back.
(at around 49 mins) When Colin is interviewing Fitzy as his "lawyer", Fitzy is seen talking on the phone but when the camera goes back to Colin you can see Fitzy in the mirror with his hands folded not using the phone. The camera then goes back to Fitzy and he is still on the phone.
(at around 7 mins) At Sullivan's graduation ceremony right after they are dismissed, one of the other graduates congratulates Sullivan for being "assigned to plainclothes right out of the gig". After graduating a police academy, nobody goes straight to anything except the next stage of their training, which is road patrol with a field training officer assigned to ride with you for several months to further evaluate you, because when police cadets graduate the actual Academy, they are still in training until they complete their field training program and their probationary period. In the north east, between the police academy and the field training program, Sullivan wouldn't even have been on his own on patrol for almost a year. Normally, to get to plainclothes takes many years.
At the top of the frame during a wide shot of the police boardroom, a boom mic can be seen.
As Sullivan investigates the site where the bodies of the Providence thugs were found, a police cruiser has "Lynne Police" stenciled on its side. The city of Lynn is not spelled with an "e".
(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.
(at around 38 mins) Early in the film, when Sullivan switches SIM cards in the phone booth, he has a Sprint RL7400 cell phone, which doesn't use SIM cards. The SIM card is also placed in the phone upside-down.
(at around 1h 6 mins) The microprocessors sold to the Chinese government agents are simple 8/16bit MCUs manufactured by STMicroelectronics. They have 6 KBytes RAM and 128 KBytes Flash ROM, and are sold at every electronics store. You might get a rocket in the air with that kind of CPU, but not very accurately. However, someone mentions later that the Chinese got busted with a set of "lamp sockets", and asks what Costello did with the real microprocessors.
(at around 54 mins) When Costigan is taking Oxycontin, the prescription label doesn't list the strength, and the tablet is a medium-sized white oval, like Vicodin or Motrin 800. Oxycontin is a brand name, round pill that comes in a variety of strengths and corresponding colors (white=10mg, orange= 40mg, dark green=80 mg, blue=160mg).
(at around 2h 20 mins) 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, thus moving back inside. However, after Brown is shot, the elevator does not move at all.
(at around 1h 45 mins) When Queenan is thrown off the 344 Wash building blood is splattered upwards first and then his body hits the ground. Furthermore, a lot of bright red blood is splattered upwards whereas when we get a shot of Queenan's body on the ground there is very little blood visible, and the blood that is visible is dark red.
(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.
(at around 1h 55 mins) When the TV news reports on a body "found in the Fenway marshes," the TV shows a body being removed from a marsh somewhere on the waterfront. The Back Bay Fens are not on the waterfront.
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.
(at around 22 mins) When Billy is in a bar, meeting Mr French for the first time, he walks near a payphone after punching a guy at the bar and pulls his jacket down. In the next shot, his jacket is back on again.
(at around 2h 15 mins) When Costigan is shot in the elevator, the pattern of the blood splashed from his brain on the elevator's inside wall is different between shots. In the next shot, blood on the wall is as dry as a bone.
(at around 2h 15 mins) When Costigan ambushes Sullivan on the roof, he kicks shut the door leading up to the roof. However, in the next shot, Costigan kicks the door again because it is ajar.
(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.
(at around 51 mins) When Billy visits Madolyn, the Microsoft Anti Spyware window on her monitor disappears and appears in different shots.
When Costigan attempts to arrest Sullivan on the roof, some rigging appears in the sky.
(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.
(at around 1h 40 mins) When Queenan gets on the train at Park Street station on his way to meet Costigan, Costigan calls him and tells him to get off at the next stop; Queenan responds, confirming that the next stop is South Station. The stop after Park Street is Downtown Crossing, not South Station.
(at around 2h 10 mins) On the envelope Madolyn receives, Colin's address is shown as 20 Pickering in Boston. Pickering Ave. is in Roxbury, nowhere near Beacon Hill. The ZIP code shown is 02459, which is Newton Centre. In the DVD version, the ZIP code is 02149, which is Everett. Billy's return address is on Conant St. in Boston, but Conant St. is in Revere.
When Costigan pulls Sullivan into the elevator near the end of the film, Matt Damon doesn't react for a split-second, waiting for his cue.
(at around 1h 40 mins) In the subway scenes Queenan and Costigan enter car #01844, but when they leave they exit car #01884.
When Colin is instructing the police officers following Queenan from his office, the Walkie talkie radios being used wouldn't transfer at that range (distance).
(at around 2h 15 mins) After Costigan is shot and killed, and his gun is kicked from his hands, if one listens very, very closely, one can hear the sound of a camera shutter firing. (This indicates that a publicity photo was being taken while the scene was being filmed).
(at around 1h 59 mins) When Bill, Costello, and Mr. French are driving towards the Gloucester cocaine warehouse, shots inside the car show them crossing the Zakim bridge northbound. Shots outside the car show them heading towards the bridge southbound.
(at around 35 mins) After Mr. French breaks and tears off Costigan's cast, the arm is naked with a small amount of bandage in the palm which Costigan then tosses aside. After a brief cut to Mr. French watching as Costello grasps and positions the bare arm, it is again covered in white gauze bandage throughout Costello "beating" it with the boot and the end of the scene.
(at around 15 mins) When Costigan is talking to his uncle while his mother is dying in the hospital, a fire extinguisher is on the wall in the hospital hallway. When the scene cuts to the uncle and back to Costigan, the fire extinguisher is gone, but the hook is still visible.
(at around 2 mins) When Frank is in the diner in the beginning with young Colin, the package of lighters, the gum, the Halls cough drops, and the mints are rearranged in each shot.
(at around 33 mins) When Costigan and Costello meet at the bar for the very first time, Costigan's cast is bright white, and the top edge is very smooth and straight. Next after Costello calls him to the back room (I ain't the cops, and I ain't askin'), the cast is clearly different, a much duller shade of white, and the top edge of the cast is very frayed.
(at around 38 mins) As the Providence thugs bodies are being photographed, the initial close-up shot of the body in tan trousers has the feet close together, right calf laying on the left ankle. In the subsequent full view, the legs are moved, with the left leg tucked up more so the right knee is laying over the left calf.
(at around 59 mins) When Ellerby briefs the cops in to the surveillance operation he turns around from watching the monitor and stands still. In the next shot he is still doing the turning motion while continuing the sentence.
The fingers of a severed hand will naturally curl inwards. Costello's bloody severed hand is an obvious prop.
(at around 1h 40 mins) As Queenan leaves the South Station T stop to walk to the South Boston warehouse where he is to meet Costigan, he walks north, away from South Station. However, South Boston can be seen behind South Station, in the opposite direction.
(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.
In the last scene, when Colin is shot and falling, you can see the stub of the tube used to splatter the blood.
The building addressed "344 Washington" is clearly in the Fort Point Channel neighborhood, just off of Congress street near the Courthouse T stop, looking northwest toward Atlantic Avenue and the Financial District. Fort Point has no Washington St.
(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.
(at around 2h 10 mins) Mandolyn tells Colin that you can tell the sex of the baby in the ultrasound, it is virtually impossible to tell the sex of a child before 4-5 months and one would be showing by then and Madolyn is clearly NOT showing by then she can't have possibly known the sex of the baby.
(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.
(at around 1h 15 mins) When Billy confronts the guy who robbed the armored truck, he pulls a Walther PPKS 380 caliber semi automatic pistol, he shoots the guy in the knee when you see the gun again the hammer is not cocked which it should be after taking the first shot.
(at around 1h 10 mins) When Madolyn first moves in with Sullivan, he teases her for her box of nostalgia after looking at her childhood photo. A few scenes later when Costigan stops by her place while she is packing, the same photo is up on the wall of her place.
(at around 1 min) At the beginning of the film, "some years ago," the sign in the convenience store window advertises The Boston Phoenix as a free paper. Before 2000, the Phoenix cost $.35-.50 (depending on the year).
(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.
(at around 24 mins) At the early police briefing on the Chinese threats of getting chips for their long distance rockets, the missiles on the screen are Russian SAM anti-aircraft rockets.
(at around 58 mins) When Billy leaves Madolyn's office after she refuses to give him a prescription for Valium, she writes the prescription and goes after him without her jacket. In the next scene, she's catching up with him outside the building and wearing her jacket.
(at around 2 mins) When Costello enters the convenience store in the beginning of the movie, the cigarettes behind the counter include a blue Marlboro box, which was introduced in the mid-to-late 1990s. When Colin was a boy, Philip Morris USA's flagship Marlboro label had only 2 selections: Regular (a red box) and Lights (a tan box).
(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."
(at around 1h) When Sullivan enters the surveillance room monitoring the microprocessor transaction between Costello and the Chinese, Barrigan and Brown are with him. In a following shot, however, Brown can be seen sitting at the far left of a table watching camera monitors with his coat off. In the next scene, he is standing next to Sullivan again and his coat is back on.
(at around 2h 5 mins) When Billy discovers the Citizens envelope on Colin Sullivan's desk, the word "CITIZENS" changes from a neater, italic-like handwriting when under the pile of papers back to Billy's original handwriting after being pulled out.
When Billy is at Queenan's house, sitting on the bench with photo frames and pictures on the wall behind him, a frame depicting "the Last Supper" appears and disappears when shown from different angles.
When French is holding the bag with the hand he places a ring very close to Costello's cheek. A second later, without him having moved, the hand is at jaw level and farther away.
Trooper Brown and Costigan know each other at the Academy in the beginning. Brown mentions after shootout that he remembers him. The cops have been watching these guys for months and Brown didn't make the connection sooner. Even if Costigan's fake cover story as an academy drop out was know, Sullivan would have been more eager to peg Costigan as the "rat" earlier.
(at around 2 mins) When Frank picks up a Bic lighter at the luncheonette counter after talking to young Colin, you can see the "BIC" in yellow on the plastic part of the lighter. Bic didn't mark their lighters on the plastic until a few years ago.
(at around 5 mins) When Colin is playing rugby near the start of the film he is playing the position of flanker, but he is wearing the no. 10 shirt, which is the position of fly half. However, some of the players have the same numbers (blue team has 2 number 5s), are out of position (like a 5 and 8 on the flanker spot), both teams have players wearing jerseys in completely unrelated colors (red team has a guy in white) and half of the players are wearing jerseys without numbers on them. Apparently, they didn't care what jerseys they wore.
(at around 3 mins) In the early part of the film, we see an issue of a Wolverine comic book. That particular series didn't exist until the 1990's.
(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.
(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.
(at around 1h 15 mins) When Billy shoots the drug addict in the knee, he is using a Walther PPK. While the PPK is double action, the hammer should remain back after he shoots him.
(at around 1 min) In the opening scene, dated "some years ago," the Boston Phoenix honor box outside the shop uses a logo that was introduced in 2005. The honor box is the same in subsequent present-day shots.
(at around 2 mins) When Costello enters the convenience store in the beginning of the movie, The Halls cough drops, located on the counter, have a modern logo.
(at around 25 mins) UMass Boston is mentioned as being in South Boston. It's very close to South Boston, but it's actually in Columbia Point, Dorchester.
(at around 46 mins) When Billy and Costello are sitting in the restaurant, Billy has a cigarette in his hand and in the next shot, he is blowing smoke rings, without taking a puff.
(at around 1h 55 mins) When Costello's motorcade is crossing the Bunker Hill/Zakim bridge, a close up of the lead car's front license plate can be seen. The font is incorrect for Massachusetts license plates. At no time in the modern age has the state of Massachusetts used that particular font for any state issued plates.
(at around 53 mins) When Billy is talking with Madolyn for the first time in her office, the position of the tissue sticking out of the top of the tissue box on Madolyn's desk changes a few times.
(at around 46 mins) When Costigan and Costello are in the diner with the priests and the nun, Costigan's necklace switches from under his shirt to in front of his shirt and then returns to back under his shirt for the rest of the scene.
(at around 55 mins) When Costigan meets with Queenan and Dignam under the bridge, Dignam's hair is messed up. From behind, his hair is perfectly straight.
(at around 1h 14 mins) When Colin is telling Madylon about how he "Cannot allow you to jeopardize an ongoing investigation...", he lightly puts his hands around her neck and face. When the shot changes and he continues with "...Or your life" his hands are back and he reaches for her face again.
(at around 1h 30 mins) When Sullivan is checking the street surveillance camera, the envelope is propped up on his coat, which shows tan and blue fabric underneath it. When the angle changes to show just the envelope (and when he picks it up at the end of the scene), it is laying flat and only the tan material of the jacket surrounds it.
(at around 1h 9 mins) When Costigan talks to Madolyn at the café, we see him leaning over the table and then pulling away in a back shot. Then the shot cuts to front and we see him still leaning over the table.
(at around 2 mins) When Frank is in the diner in the beginning with young Colin, he has the counterman put Shop Rite brand milk in the bag. At the time of filming, Shop Rite did not have any stores north of Connecticut.
(at around 1h 21 mins) When Billy goes over to Madolyn's apartment she makes him some tea. While he drinks the tea she says his vulnerability is freaking her out. The front shot of her shows her bending to lean her head on her raised, outstretched arm. Immediately, the shot from the back of her shows her standing upright and arm at her side.
(at around 1h 45 mins) After Queenan is thrown from the roof, we see Costigan's POV shot. When Costigan moves his head slightly to the right, the dolly track appears briefly.
(at around 30 mins) When Costigan is getting his arm put in plaster his stare is toward two totally different places between shots.
Based on the view of the State House from Sullivan's apartment balcony, he lives on Tremont St., just north of the Park St. intersection (see reference to Pickering St envelope address goof).
(at around 1h 14 mins) When Madolyn and Sullivan make out in his apartment, just after the phone call he received from Costello, their hands change position between shots multiple times. His hands switch from being on her face to being out of shot and back again, and her hands switch from being on his chest to being out of shot.
During the final shootout between the baddies and the cops, the pilot window of the grey GM is destroyed but appears perfect a second later.
When Costello and French encounter the cops, the first shot shows the cops' car turning their lights on. In a new shot a second afterwards the lights on the middle and right side cars are out and they are turning them on again. On yet another new angle, the lights on the car on the left turn from off and on again in a split second.
While Queenan is talking to Costello out on the street, watch the people behind him. First there's no one, then we have a shot of a woman and a huge line of kids passing next to her. Then back to Costello and the woman, who hasn't moved, is now miraculously visible behind him. To add to the mess, the kids have vanished.
In the scene after Queenan dies, when Sullivan picks up his phone, the number Sullivan calls Costigan in isn't the same as the one from which Costigan calls back, even though it's the same mobile (silver and blue vs. Costigan's red phone for Costello's gang). When Sullivan calls, the number begins with something like "617-854" and when he sees Costigan calling back, it's "617-177".
In the beginning when Costello is saying: "You could become cops or criminals", he has a cigarette in his mouth, but when he leans into to say: "whats the difference?", it disappears.
When Frank and Francis executes the couple on the beach, the woman falls almost on top of the man's back. When it cuts her body has almost moved off him. Then in the next shot she is on top of the man again.
When Costello's bad guys are pulling up in the van to the building where Queenan and Costigan are talking, you can see the wet tire marks where the van stops before it gets there.
Before French dies he starts to cough and there's suddenly less bullet holes in the windshield than in the previous shot.
After the football game, when Sullivan turns around to insult the other team, there's a guy with a light blue shirt that steps ahead of another one with a dark blue shirt. A second later their positions swap.
After the beach scene, Costello is preaching young Sullivan on loaded guns. His cigarette disappears from his lips between shots.
While running from the cops, French turns the car 90º to the left, but from a different angle it's still facing in the original direction.
Costello tells Costigan "your dad had his own code". Then Costigan turns his head and exhales some smoke, but the following frame shows his head in the opposite direction and the smoke is gone.
Costigan enters the bar and points at a guy with a leather cap. In the background, a waiter is leaning on the bar, who then stands up and starts to walk. In the following close shot he is back in the previous place, leaning.
After the football game, Sullivan turns to his right to call the other team "faggots". From a different angle he is making a left turn.
While Sullivan is rain drenched in military school, when he says "Sir! Yes sir!" his hair style changes in a nano second.
When Dignam (Mark Wahlberg) reports the processor theft to the SIU detectives, he says 20 chips were stolen. When Fitzy opens the case at the sale, there are 66.
In the restaurant, after Costigan says "School is out," he starts to bring the cigarette to his mouth, but before he smokes, while the action, music and dialogue continues, the shot cuts to him already exhaling the smoke.
When Costello lies dead in the shovel of the excavator, his right arm moves between shots. (First it is up - in the far shot, it is down).
When Sullivan is checking the CCTV recording, we can see the "citizens" envelope, lying on his coat, on a desk or a chair. First, the folded part of the envelope with "citizens" written on it is upright, with the word appearing upside-down. Then, as he grabs his stuff to leave, the position of the envelope has changed to horizontal.
In the scene in a bar where Costello talks to the young Colin Sullivan, the time in his watch is evidently very different in two shots (when he takes the money from the bar owner and later when he hands Sullivan a bunch of coins). First it reads 2:50, then 2:58, and only one and a half minute has passed in the movie, as shown by Costello talking. Also, the watch in the second shot has no seconds hand, only hours and minutes.
When Sullivan is analysing the Providence corpses, the close-up shows both of his hands together, but on the wide shot one is near the corpse, and the other one close to his hip.
When Billy is sitting inside Queenan's house, the glass of water is in his hand in one shot, disappears in the next and then returns.
The position of Madolyn's spoon while eating the chocolate cake is not continuous in the front and back shots.
When Sullivan is questioning a bad guy, he sits down with a cell phone right in front of him. But later on, he reaches out to our left to grab it.
After Costigan comes out of jail he visits an old lady. From a front shot she is slightly leaning, her left hand unseen. From a back shot the left hand is standing out over his shoulder with a burning cigarette. It should have been visible from the opposite shot at first.
After Costello smashes Costigan's wrist he hands all of the dollars he has in his right hand. A frame later money reappears in the hand.
When Sullivan crosses the street there's a lot of people going to the right. From the CCTV recording there's just one person.
In the final scene of the movie, when Sullivan is walking down the hallway and into his apartment, his belt is light brown. But when he's dead on the floor, it's a dark brown, almost black.
At the very last shot of the movie, taken from inside Sullivan's apartment, the Massachusetts State House appears to be quite closer than in other shots from the apartment - e.g. when Sullivan first rents it.
When Costello is getting his money in the diner, young Sullivan is first sitting next to some packages on the right of the screen , but a shot later, when he stands up holding a brown paper bag, he is seen sitting next to to an empty seat.
When Billy and Costello are talking in the bar, after Costello fires the paper cloth, smoke is visible in the shots involving Billy, but not in the ones involving Costello.
When Sullivan and his pal are watching the golden dome building from a bench, from a back shot his friend has his head faced straight, but from the front shot it's sideways.
The dead woman on the beach lies with her feet together, but a shot later they are spread apart.
During the opening scene at the diner, Costello places a comic book in the grocery bag, and it is well below the top of the bag. In the next shot of the bag, the comic book is much higher in the bag, and in fact is almost rubbing the boy's cheek.
When Costello is hitting Costigan's broken wrist, as Costello is leaving the room, the shot shows Costigan crumpling to the floor beside the pool table. He is on the floor as Costello is leaving. But, the next shot shows him back on the pool table crumpling to the floor again from a bird's eye view.
When Costello and Sullivan are in the porno theater, Costello's line is "it won't be me who suffers for it."When the tape is played back to Madolyn later, it says "it won't be me who pays for it."
When Costello tells the girl he has a hard-on, the position of her fingers on the blue book keep changing.
While having dinner, from a side shot we see Sullivan's mouth chuckle. Frame later, from the front, he is serious and smiles half a second afterwards.
When Ellerby attacks the guy for not installing the cameras in the right place, he knocks off a map from the board. A second later Ellerby is still going after him, and the map is fixed.
In the scene after Queenan dies, when Sullivan picks up his phone to contact Costigan, he presses the "talk" button and a smudge of blood is left. In subsequent shots, there's no trace of blood on the "talk" button.
When Costigan is with Madolyn in her office, the tissues in the tissue box change consistently between shots.
When Billy Costigan is at the funeral near the beginning of the movie and reads the card signed "From Frank Costello," it is initially seen as a heavy bold script, but in the closeup, it is a thin script written in different handwriting.
At Billy's mother's funeral, the signature of Frank Costello on the flowers changes between shots.
While Costigan is having coffee with Madolyn, a coffee cup suddenly appears in his hands close to his mouth, and the toothpick that was in his mouth a second ago vanishes.
In the scene where Alec Baldwin is briefing the cops on the micro processor bust, his shirt has distinct sweat patterns. These patterns change between scenes, back to original then finally almost dry.
When young Sullivan is at Mass, a priest is swinging the smoking incense burning. In the next shot the smoke is gone, and he is away, arriving with the burner and repeating the previous movement.
The top layer on their dessert changes when Sullivan and Madolyn are in the restaurant. Between shots, the top piece changes back and forth between flat and curved.
When Billy and Frank are sitting in a bar, Billy is just sitting at the table. In the next shot he's suddenly in the middle of blowing smoke rings into the air.
When Costello's men drive off, after throwing Queenan off the top of the building, the state troopers are firing at the van. One back window is shot out, then in the next shot of the van the other window is shot out and then the same one is shot again so the one window is shot out twice in the same scene.
In the shootout at the elevator near the end of the movie, when Sullivan shoots the last guy, you can clearly see kneepads under his pants, to soften the fall.
In the Porn theater after Frank reveals the dildo to Sullivan and they argue about it, when the camera zooms out and the view is behind Sullivan the guy to the far right looks like he was added post production.
When Mr. French smashes Costigan's arm cast, on the second attempt Costigan seems to be using his own force to smash the cast. As French loses his grip at the top of the motion, Costigan's arm moves downward with all the force it would have had had French not let go.
In the scene where Costello is smashing Billy's hand with the boot heel, you can tell from the position of Billy's arm that Costello is hitting the pool table rather than Billy's hand. He is actually hitting his own hand more than he could possibly be hitting Billy's.
When Billy shoots the guy in the knee the hammer of his gun is not cocked as it should have been after firing a shot.
(at around 1h 10 mins) When Colin and Madolyn are talking in the kitchen, while she moves in, the cabinet doors go from open to closed repeatedly.
Just after Billy Costigan is shot, the elevator doors try to close. In the shots where the black guy comes out of the other elevator, the doors aren't moving anymore.
When Costigan is with Madolyn in her office. Madolyn doesn't have jacket on but when she runs out after him to give him a prescription she has a jacket.
In one of the opening scenes, when Queenan and Dignam are first interviewing Billy Costigan and Colin individually, Dignam refers to himself as a "staff sergeant." However, the Massachusetts State Police has not had staff sergeants since 1992.
When Costigan is riding the "T" (Boston subway), he is talking to Queenan on a cell phone. However, they are on the "Red" line, which is obvious because of the red walls in the tunnel. Cell phones don't work on the Red line because it is underground and there are no cell phone routers in those tunnels.
When Queenan and Costigan are riding the Red Line, Queenan gets on at Park Street station. Costigan tells him, "Get off at the next stop, South Station." South Station is two stops away; the next stop after Park Street is Downtown Crossing. However, Queenan does get off at the next stop, and it is magically South Station.
In a scene between Madolyn (Farmiga) and Sullivan (Damon) as she is moving in he pulls out a framed picture of her as a kid. Several scenes later as Billy (Dicaprio) meets her at her apartment for their tryst, the picture is hanging on the wall. Sullivan rehangs it.