Factual error: Haloclines are referred to throughout, and depicted occasionally as some sort of underwater tornadoes. Haloclines are in fact just salinity gradients, and look nothing like they do on the show.
Character mistake: A shot shows Djimon Hounsou completing his year entry on a large chalk board. The entries are 20 years apart. The third entry on the second line is 2274, the next should be 2294, but instead it records 2394. The one after corrects the sequence with 2314. Considering there is an entry only every twenty years, you would think he'd be more careful. (00:20:15)
Continuity mistake: When Miles jumps off the ferry to swim ashore, the camera view is from the ferry: he jumps into quiet, fairly level water, yet the camera recedes from him (he jumped off the back of the boat as the camera continues moving with the boat). The angle changes and we see the wake of the boat - but it's not what he jumped into.
Factual error: The depiction of the hanging is completely inaccurate. By the 1890s, the gallows at Newgate were housed in a room within the prison, not in the courtyard. Prisoners' wrists and legs were pinioned before they were hanged, not left free as depicted. The long drop was used in Britain from the 1870s, not the short drop depicted. The large knot depicted was not used in Britain (although it was in America) ; a simple sliding loop was actually used, and this was positioned under the jawbone at the side of the neck, not at the back of the neck, which would quite probably not have broken the neck, leaving the person to strangle to death.
Revealing mistake: Hannah sits in a conference room and pulls a landline phone towards her to dial her friend, asking about the will Owen left. The phone however isn't in any way connected, hence no call could have taken place.
Continuity mistake: Kurt is still recovering from the beating he took in the previous episode with bad cuts on his forehead, checks and temple area. They are red and impossible to miss while he is in the police station. The cuts have miraculously disappeared in the next scene when he goes to visit Mona.
Continuity mistake: Tony Sparkle is seen defacing a picture of Judy Talent. He starts writing something beginning with T. The action cuts away for a moment, and then back again. The words on the picture are "SAD OLD BAT". (00:07:05)
Factual error: A scene in a photographic darkroom shows Michael Gambon developing a colour print in a dish under safe lights. Not possible. Colour printing must be carried out in pitch dark usually inside a light tight print processor, as colour photographic paper is sensitive to all wavelengths of visible light.
Revealing mistake: Mr Knight shoots Suzie Boreton - after the muzzle flashes and sounds stop the bolt of his MK14 EBR continues to move back and forth as if it's still firing. (00:30:30)
Episode #3.1 - S3-E1
Continuity mistake: DI Chandler calls a suspect "Daniel Wilkie." However when the interview is done he goes and talks to Ed, saying "you've just arrested Ben Wilkie."
Continuity mistake: Early in the episode as she is on a fire escape looking to hide somewhere, the window she opens from the outside has two half panes of glass, but on the inside it only has one pane of glass.
Factual error: Chief Superintendent Hilton wears the ribbons of the General Service Medal (awarded for military service in a combat zone, most commonly in Northern Ireland) and the Police Long Service and Good Conduct Medal (awarded for twenty years' service), but not the Golden Jubilee Medal (awarded to all officers with five years' service in 2002), which he would also have. When he reappears in Series 4, he is wearing the Golden Jubilee Medal, Diamond Jubilee Medal (awarded in 2012) and Police Long Service and Good Conduct Medal, which would all be correct, but no longer has the General Service Medal.
Is Lupin Burning... ?! - S1-E1
Other mistake: The logo of the evil organization, Scorpion, contains just a little misspelling. It's missing the R. (00:02:50)
A Single Piece Was Lost - S1-E10
Visible crew/equipment: When the Gruenaks attack the Scientist a puppeteer is visible to the right of one of the Gruenaks, just before it grabs the bird cage and throws it onto the Scientist's head. (00:28:18)
The Secret Fate of All Life - S1-E5
Continuity mistake: The first time we see Detective Cohle being interviewed by the other two detectives, two of the beer cans on the table in front of him completely vanish between shots when he asks to see the rest of the discovery file.
Factual error: The show, which is set in California in 1947, mentions the gas chamber, lethal injection and the electric chair as methods of execution in the state. Two murderers are sentenced to death by lethal injection and one is depicted being instead executed in the electric chair, which the governor states has been brought out of retirement for the occasion. In fact, California adopted the gas chamber as its sole method of execution in 1937 (having previously used hanging). Lethal injection was not used in the United States at all until 1982 and not adopted in California until 1993 (becoming the prime method in 1996). California has never used the electric chair.
The Mind of Simon Foster - S3-E23
Continuity mistake: When the pawnbroker closes his metal gate, he's facing the wire mesh. When the shot cuts, he's instantly facing away from it. (00:10:15)
Revealing mistake: When the thief places The Blue Carbuncle in the goose's throat, it's obvious he actually doesn't put the gem in the bird's mouth. He pretends to, but then drops the gem into his other hand. This is all visible in the shot.
Us vs. Them - S2-E2
Factual error: We see Liam's driver's license. It says he's from Rhode Island, but the license looks nothing like RI's. It's issued by the State Motor Vehicle Commission, but RI does not have an MVC (only New Jersey does). And the expiration date is always the same as the holder's birthday, but here we see it's 2 days after his birthday.