Plot hole: Unless Jarvis Goodland has the world's most stupid lawyer, he has nothing to worry about. Columbo searches the greenhouse and uses a metal detector to find the bullet which, supposedly, shows Goodland's gun is the murder weapon. He conducts the search without a warrant and against Goodland's wishes - he asks him several times to desist with the search and leave. Any evidence discovered or collected during the search is inadmissible in court.
Plot hole: Dr Kepple is finally caught when he rushes to the hiding place of the calibration converter that he hid in the lamp after the murder. Why is it still there? It was a great hiding place initially when the police were searching people and the building in the hours after the murder but Kepple had plenty of opportunities after that to get rid of it. It is the only piece of evidence linking him to the crime and it is in his office so you would think that his main priority would be to dispose of it as soon as possible.
Plot hole: Just before Joe Devlin kills Vincent Pauly in the hotel room, he picks up the Full's Irish Dew whisky bottle with his bare hands. The same bottle falls to the floor when Pauly is shot, and Devlin then kicks it over to the body. Devlin didn't wipe the bottle clean at any point, therefore it will be covered in his fingerprints, but this is never mentioned throughout the episode. There's no way the police would overlook such a basic clue.
Continuity mistake: Dr. Murcheson is not wearing gloves when he scrapes the women's faces. Then he goes into another room and removes a gray glove from his left hand.
Dead Weight - S1-E4
Character mistake: When Columbo first comes to the general's apartment, the general is showing Columbo a submachinegun. He also shows him a magazine and says it is an "extra clip." A retired general would know the difference between a clip and a magazine; the terms are not interchangeable.
Columbo and the Murder of a Rock Star - S10-E3
Factual error: They talk about Wednesday as day of the murder. On the other hand, we see a speeding ticket with 3-11-91. In 1991, March 11 was a Monday and November 3 was a Sunday, so whichever way the date is written the day is wrong. (01:17:53)
Columbo and the Murder of a Rock Star - S10-E3
Factual error: Champagne corks have a metal cap between the cork and the wire cage. (They can be seen when both Creighton and Columbo open bottles.) When Creighton injects the chloral hydrate into the champagne, he does not have the difficulty he should have getting through the metal. The needle does not come out damaged as it should, and it did not go far enough into the cork to put the liquid into the champagne-it would get lost in the cork itself.
Character mistake: Piloting a helicopter, Leslie ends a radio conversation by saying "Over and out." "Over" means "I'm done talking; please respond." "Out" means "I'm done talking and I'm ending this communication." An experienced pilot would never say "Over and out." They are two different terms.
Deliberate mistake: Beth shoots Bryce three times in the chest, and he falls face down on the floor. She then drags his body across the floor, also face down, to in front of the sliding door, but there is no sign of blood anywhere.
Character mistake: In the performances, Benedict is not conducting; he is waving his arms around.
Factual error: When Mrs. Williams takes Columbo flying, she does some aerobatics. Neither of them is wearing a seatbelt. No pilot would do that.
Death Hits the Jackpot - S11-E1
Continuity mistake: After Lamarr takes off Freddy's undershirt we see the level of the water in the bathtub. Then he drags Freddy over to the tub and breaks his watch. At that time the water level is lower than it was before, even though the water was still running.
Revealing mistake: At the end when Laurel and Hardy are licking Columbo, a substance is caked on Columbo's neck, presumably the food they used to get the dogs to lick Peter Falk.
The Bye-Bye Sky High I.Q. Murder Case - S6-E3
Factual error: A "silencer" (properly called a "suppressor") does not muffle a gunshot to a whisper. An unsuppressed gunshot is about 160 dB, equivalent to a jet airliner taking off, but a suppressed gunshot still registers about 100 dB, equivalent to a power lawn mower. Also, a suppressor on a revolver is totally useless, because most of the noise comes from the gap between the front of the cylinder and the rear of the barrel.
The Most Dangerous Match - S2-E7
Factual error: Clayton tells Columbo that he had purchased a new transistor for his hearing aid. Hearing aids - even the old types in use in the 1970's - do not have any user-replaceable parts. The only thing that can be replaced is the battery.
Other mistake: Several of the English characters change back and forth between calling Columbo "leftenant" and "lootenant."
Other mistake: When Benedict puts his briefcase in the back of the Jaguar, the hatch does not close properly. It is still not closed properly when he picks up the car from the repair shop.
Murder with Too Many Notes - S13-E4
Other mistake: In the movie within the story the murderer repeatedly stabs the victim and pulls back the knife. Even after several stabs there is no blood on the knife.
Factual error: Columbo asks for a red wine. His host orders a Beaujolais but the butler brings a Bordeaux. Beaujolais is from Burgundy, not Bordeaux. (01:18:40)
Dead Weight - S1-E4
Other mistake: Columbia calls Helen Stewart from a pay phone. He dials only six numbers, not seven.
Answer: "Apparent" drowning answers your question - things are not always as they seem. Drowning could be accidental, but it could also be a murder in disguise. Moreover, the actual cause of death has not yet been determined - accident, suicide, murder, or natural cause (e.g, heart attack while swimming). Columbo would be there to investigate if anything looks unusual for it to be a mere drowning or if there is evidence or suspicion of something else.
KeyZOid
This was just on TMZ.com's "Aaron Carter Dead at 34" (11/05/2022): "Law enforcement sources tell TMZ... homicide detectives have been dispatched to the scene but we have no information or evidence of foul play. It's standard operating procedure for homicide detectives to investigate such [drowning] death scenes."
KeyZOid