Factual error: The snub nosed revolver used by Miss Fisher, a J-Frame S&W, was not produced until 1950.
Factual error: There is no way Laurel Lance would have been allowed on the prosecution team for Moira Queen's murder trial. Due to the facts that she both dated and as a lawyer represented the defendant's son, the defendant's daughter used to intern for her, and her boyfriend was one of the people killed in the Glades, it would have taken all of two seconds for the court to have her removed if she didn't willingly recuse herself, since her presence would be a major conflict of interest.
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.
Factual error: Noticed this watching season 2, and I assume it was also the case in season 1. The entrance of the Miramar Playa has flags from various countries flying. One of them is the Canadian flag with the maple leaf. Wrong flag. In that period the Canadian flag was the "Red Ensign", or "Dominion Flag." The maple leaf flag wasn't introduced until 1965.
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.
Factual error: A plastic bag of items is found under the footboard. Plastic bags weren't invented in 1969. They first appeared in public in 1979.
Enough Nemesis to Go Around - S3-E1
Factual error: The 1-ton electromagnet is supposed to have moved only the bullets without affecting the steel elevator car at all. This is impossible.