Factual error: An important plot point is that diamonds do not burn and can be recovered from the ashes of a cremated body. This is completely wrong - diamonds would combust freely at cremation temperatures, and since they are pure carbon they don't even leave any residue.
Factual error: Devlin proclaims himself to be a staunch Irish Republican but he refers to the Northern Irish city of Derry as "Londonderry." This is the name imposed upon the place by the British and is despised and rejected by Republicans. Devlin would refer to the city as "Derry."
Factual error: At the crime scene, the landlady of the dead man is brought into the room in order to identify one of the dead men. This is never, ever done - she could contaminate the crime scene in a dozen different ways. She would be asked to identify the corpse at the morgue after the scene had been cleared by forensic examiners.
Factual error: Despite the fact that other officers are doing so, Columbo does not wear gloves while examining the crime scene. He also eats and drinks in the room - both absolutely forbidden - leaving eggshells scattered about the place. The crime scene is now totally compromised and nothing found can be used as evidence.
Factual error: In common with many other episodes neither Columbo, the attending police officers or forensic investigators wear gloves or other sterile gear while examining the murder victim's body or the crime scene. Columbo hands out bananas to other people on the scene which they happily eat. The senior crime scene forensics officer, Kingsley, hands out coffee and doughnuts! Eating and drinking are absolutely forbidden on a sterile crime scene, which has been hopelessly contaminated with fingerprints anyway.
Factual error: In the middle of summer in southern California, water spread thinly on an outdoor ceramic surface would start evaporating immediately and would be gone in about fifteen minutes. The surrounds of the pool would be bone dry by the time Columbo arrived at the scene, nearly an hour after the murderer sprayed the water there.
Factual error: Columbo parks across the street from a house where a murder has occurred. The address is given as 1278 Fairfax Drive. Columbo investigates and returns to his car. A house number, 400, is painted on the curb. The house across the street from 1278 would have an odd number, probably 1277 or 1279. It would not be 400.
Factual error: When Columbo initially latches onto the radio dilemma (which ultimately solves the case) the dial is tuned all the way to the left. He later tells someone that the radio is set to 'Classical 52', but an AM radio starts at 54, meaning 540KHz. There is no 52.
Factual error: Near the end of the episode, Jackie Cooper fires a bullet into his hotel room from the balcony using a revolver fitted with a silencer. Hayward also uses a revolver with a silencer to kill Stone. This is a classic Hollywood error, as silencers do not work on revolvers (unless noticeably modified), due to the gap between the barrel and the cylinder. They also don't make gunshots nearly as quiet as shown.
Factual error: In the series, Columbo does not carry a gun, and in several episodes it is mentioned that he doesn't like guns and/or that he doesn't know very much about them. In the real world, all LAPD officers must carry guns, and they must re-qualify with them at the range six times each year. Also, due to the very nature of their work, they are knowledgeable about numerous types, makes, and models of guns.
Factual error: The license plate on the automobile of Stallions football team owner Fred McBain reads STALLION1, but personalized California license plates can not have more than seven characters ( http://www.vanityplatebystate.com/alphabetical-listing-of-states/california/).