During Verbal's interrogation, his coffee mug looks half-empty when he takes the first sip. In the next scene, there is suddenly more coffee in his mug.
Shot of a landing Jumbo Jet (four-engined Boeing 747) becomes a twin-engined 767 a moment later.
Prior to lighting the police car in fire, the lights on the car are stepped on and crushed yet in the following shots, they are intact.
In the opening murder, the gunman is not wearing gloves. After the shooting, he is shown in close-up wearing gloves, dropping his cigarette. Then during his escape, while in shadow, he is visibly no longer wearing gloves. (Audio commentary reveals the close-up hand to be that of composer/editor John Ottman).
In the scene where Kobayashi is walking through the office building flanked by his two bodyguards, just before the camera pulls back to reveal Hockney, we see an African-American woman in a white blouse and tan slacks walking along side of Kobayashi. In the next cut to Kobayashi walking through the elevator corridor, if you look to the bank of elevators to the left, you'll see the same woman coming out of an elevator as if she had just come down from one of the upper floors.
In the hospital scenes in the burn unit, the medical staff are gloved and gowned but their surgical masks are pulled down under their chins. Their masks should be covering their noses/mouths because burn victims are extremely vulnerable to infection.
In the opening scene when the police arrive to the dock of the burning ship, there are bodies lined up up on the pier covered in body bags labeled "S P CORONER" as in San Pedro Coroner. The Department of the Coroner is a function of Los Angeles County.
Either the name of snitch Arturro Marquez is misspelled (Because in Spanish the name is Arturo - with one "r" only) or maybe is a game of words (because Turro in Argentina means artful).
During the line-up scene, as the suspects enter the line-up booth, a microphone can be seen above Hockney's position. This is a standard feature of police line-up booths. (In some releases of the movie this is not visible because the scene has been cropped vertically to change its aspect ratio.)
The robbery of New York's Finest Taxi service is a 5-man job, done with four vans, two of which have passengers not in the driver's seat. The van in front is driven by Keaton with Verbal holding the gun when the back door opens. The van behind rear-ends the car and gunmen hold guns on the cops from the driver's side of the van on the right and the passenger side of the van on the left. Who is driving the van on the left? Three guys (Fenster, McManus, Hockney) are doing four jobs (driver rear, driver left, passenger left, driver right). It's possible Hockney (in the left van) threw it into park and quickly slid over to the passenger window. But this is Verbal's version of the story, not necessarily what actually happened. It is quite possibly his mistake, not spotted by Kujan, rather than a mistake by the filmmakers.
When Kobayashi enters the lift with his two bodyguards, Macmanus shoots them. In the next shot we see that Macmanus is sitting on top of the elevator. But the blood of the two bodyguards splashes on the elevator window which in fact should have splashed on the ground since the shots came from above.
It can be argued that the blood splashed in all direction and hence came on the window, but Kobayashi who is standing just next to those bodyguards doesn't even have a drop on him.
In the first hospital scene, the Hungarian's face is burned, but his right eyebrow isn't even scorched.
Blood squib visible (at around 1h 11 mins) in the money bag as Hockney is shot.
There is no cut on the boy's neck after man slices his throat.
Saul's eyebrows are moving a bit after he is dead.
When the criminals all exit the police station, McManus and Fenster stand in front of a magazine stand with issues from several different years. The Entertainment Weekly showing Michelle Pfeiffer is from 1990, the National Lampoon is from 1991, the Newsweek about the Clinton Health Papers is from 1993 and the Advocate showing Rudy Giuliani is from 1994. A real magazine stand would not be displaying old magazines.
Dean Keaton's line "If I don't get Kobayashi my way she'll get him her way", spoken to Verbal Kint by the dock, doesn't match the movement of his lips.
During the harbour scene near the end, the report of McManus's Steyr AUG is very muted and yet he has no silencer attached.
When one of the guys robbing the corrupt cops (at around 34 mins) wearing pantyhose on his head and sitting in the driver seat of the white panel van looks back and says "hurry up", his mouth is not moving.
In the scene when the men go to ambush Mr. Kobayashi at his law offices, just after he enters the front door of the lobby with his bodyguards, crew members and lighting stands are visible in the reflection of the polished marble as the camera dollies past the column.
During Verbal's interrogation, when Dave Kujan bends over to pick up the dropped cigarette lighter, several lighting stands and a flag are visible in the background, by the desk lamp.
(at around 12 mins) After the lineup scene when the characters are moved to the cell, as Fenster begins to pace back and forth, there is a silver microphone visible underneath the bench that Todd Hockney is laying on. Two seconds later it vanishes.
In the robbery of "New York's Finest Taxi Service", the firefighters arrive wearing Los Angeles fire helmets, not the black leather helmets used by New York.
Planes landing in New York City from South America would land at JFK airport and not La Guardia airport. The arriving passenger was picked up at the departure section of the Delta building.
In the beginning of the movie, we see "San Pedro" police department. San Pedro is part of the city of Los Angeles, and as such, it would be the Los Angeles Police Department, Harbor Division.
When the police taxi service picked up the smuggler, after they were shown crossing the Verrazano Narrows Bridge, the smuggler handed the police the envelope of cash and asked if it was enough to get him to Staten Island. Having crossed the bridge, they would have already been in Staten Island. If they came from Newark Airport, they would have already been on and left Staten Island, but this wouldn't be the case as the New York City police would not have picked him up in Newark, New Jersey.
During the New York police car robbery, palm trees can be seen in the background when the car's windshield is first hit with a sledgehammer. The palm trees are more clearly seen in the full-screen version.
Verbal tells Kujan about Fenster's death (He actually says "After Fenster's death, I wanted to run away.") In that case, the police wouldn't normally just let him out so easily: This would mean confessing to knowing about an unknown murder, and he would be questioned, at least about where the body was buried.
After Verbal shoots the smuggler, Keaton opens the car door, takes the briefcase, and closes the car door with bare hands, leaving his fingerprints behind. Having been arrested before, his fingerprints would be on file and he wold have been quickly identified as having participated in the murder. If Keaton was the smart, seasoned criminal he was made out to be, he would have been more careful and not left his fingerprints behind.
While planning the robbery of the taxi service, Verbal wants to do the job without killing anyone. He later kills Saul, which would have been unnecessary during that robbery. Nobody picks up on this clue that Verbal is not who he claims to be.