Episode #1.5 - S1-E5
Other mistake: Ian is pointing a gun at Luther in the hotel. The maid starts to open the door from an adjoining room (roughly 4 meters away). Ian starts firing at the door, and Luther falls over on the spot he is standing on. Half a second later, Luther is through the door pushing the maid to the floor. What about the hail of bullets he must have had to go through to get to the door? (00:47:00)
Episode #1.6 - S1-E6
Other mistake: A detective is watching footage on a computer screen of the standoff with Luther and Reed where police snipers are on rooftops. Someone walks across the screen right behind Luther and Reed. Surely the police would have cordoned off the area with the snipers on the rooftops.
Episode #4.1 - S4-E1
Other mistake: Luther says "Budge up." The subtitles say "By jump." (The correct subtitle is in the DVD extras). (00:40:40)
Episode #4.2 - S4-E2
Other mistake: One character says "Is this another appeal to my maudlin East-End heart?" The subtitles say "eastern heart." (00:29:00)
Episode #2.1 - S2-E1
Other mistake: During the opening sequence. Sadie Buckingham walks out of Smithfield market, walks down St John's Street, Cawcross Street, then up Greenhouse Rents. This is a dead end. She next appears walking along Jerome street where she is murdered. After the titles DCI Luther walks down through the police cordon and meets Martin. In the background is Godfrey Phillips Ltd, which is a company at the junction of Commercial Street and Jerome Street. This is a 30 minute walk from Smithfield. Luther then says "is he having a joke... slaughtered like cattle next to a meat market".
