History Main / DetectiveMole

* ''Manga/DeathNote''. It isn't a particular murder, but a massive supernatural killing spree...but the killer is still called in to investigate.

* ''Fanfic/HeroChat'' has a [[ShowWithinAShow Play Within A Story]] produced by the students, which gets interrupted by an Akuma. The spin-off ''Team Miraculous" shows it in more detail, with [[EveryoneIsASuspect everyone having a motive]] and TheReveal that the detective, played by Myléne, was the actual culprit looking for a FallGuy, but is thwarted by the victim's daughter, played by Zoé, defeating her in a fencing duel, and [[JustBetweenYouAndMe having confessed to the murder]] beforehand.

** ''Series/CSIMiami'': Detective Natalia Boa Vista was originally working as an Internal Affairs mole while in the Crime Lab. This ends up causing friction with some of her co-workers when they find out.

* Detective Vega on ''{{Series/CSI}}'' turned out to be one much to the chagrin of many fans.
* Marty Pino on ''{{Series/CSINY}}'' was a coroner mole variant, processing corpses to extract drugs from organs, again to a lot of negative fan reaction.

** Played straight in ''Manga/DeathNote'': ''Literature/AnotherNote''. Naomi Misora is very impressed with Ryuuzaki's ability to decipher Beyond Birthday's [[CriminalMindGames codes]] when no one else can--of course it's because "Ryuuzaki" ''is'' Beyond.

** Played straight in ''Manga/DeathNote'': ''Literature/AnotherNote''. Naomi Misora is very impressed with Ryuuzaki's ability to decipher Beyond Birthday's [[CriminalMindGames codes]] when no one else can--of course it's because "Ryuuzaki" ''is'' Beyond.

** Sgt. Trevor Gibson in "Sleeper Under the Hill" turns out to be involved in the killings and does his best to throw Barnaby and Jones off the trail. He ultimately falls victim to his partner in crime.

* In the first-season ''Series/{{Dexter}}'' episode "Return to Sender", Dexter gets called to the scene of one of his own murders.

* ''Series/MidsomerMurders'' has one where a large sum of money goes missing, with two JerkAss "special ops" types are sent to help. Troy immediately sucks up to them, despite their contempt. In the end, it turns out they were in on the heist, with their own boss masterminding (and having done the murders, which wasn't part of the plan).

* In the ''Series/{{Columbo}}'' episode "[[Recap/ColumboS10E11 A Trace of Murder]]", Columbo immediately identifies the murderer, but doesn't realize until late that his colleague and confidante on the case, a crime scene investigator, was in on it.

* ''Manga/CutieHoney Universe'' has Inspector Genet, a lawwoman who is investigating the cruel goings on of Panther Claw, and along the way gaining the trust and respect of Honey Kisaragi. She actually ''is'' Panther Claw herself, and brags to Honey about it using her own catchphrase.

This was explicitly banned in Ronald Knox's "Ten Commandments" of the FairPlayWhodunnit story, although some authors viewed the prohibition as only applying to [[LoopholeAbuse the main investigator]] and still wrote stories unmasking a secondary member of the investigating team as the criminal.

* In ''VideoGame/PhoenixWrightAceAttorneyTheContemptOfCourt'', [[BigBad Lyle Hemlock]], the leader of the Aculeus organization, disguises himself as a detective character named Robert Snow to investigate and manipulate various people related to his organization like puppets to [[ControlFreak ensure that things always go his way]] and ultimately escape with a rare metal called enigmium, worth several million dollars in cash.

* Several episodes of 'Series/RunningMan'' set up a detectives-have-to-catch-the-thieves scenario with the latter trying to evade elimination. Of course, the producers don't say that they had to be ''different'' people. Such as in Episode 381.

* In the ''Series/{{Psych}}'' episode "Psy vs. Psy", Shawn competes with a rival psychic who turns out to be getting her information about a robbery from having been in on the crime. When Shawn puts the amount of stolen money much higher than she does, she realizes her partner is going to double-cross her, kills him, and shows up to investigate the murder. At the crime scene, she touches the body while "psychically reading" it to explain the presence of her DNA.

* '''Series/Whodunnit2013'': It's assumed the Killer is sabotaging the investigation. Downplayed, however, as ''everyone'' is sabotaging someone else's investigation to avoid being the next victim.

* '''Series/{{Witse}}''':

* 'Series/RechtOpRecht''': Johnny, Stanny's partner turns out to be this in the episode "Vuil". When his commissioner starts to suspect something, he even tries to deflect suspicion by framing Stanny. He subsequently "helps" Hugo solve the case.

* In '''Series/ShotsFired''', Platt personally leads the investigation to find Breeland's killer... who happens to be him.

* '''Series/StarTrekTheNextGeneration''': In "[[Recap/StarTrekTheNextGenerationS4E24TheMindsEye The Mind's Eye]]", Geordi is assigned to investigate a tampered cargo transporter that was used to beam Federation rifles to Krios. The person who modified then wiped the transporter is himself, but [[ManchurianAgent he doesn't remember it]].

* In the ''Series/{{Columbo}}'' episode "A Trace of Murder," Columbo immediately identifies the murderer, but doesn't realize until late that his colleague and confidante on the case, a crime scene investigator, was in on it.
* ''Series/{{Community}}: While not murder ([[SeriousBusiness it's just treated as it]]) or explicitly stated, the possibility ''is'' raised in [[''Recap/CommunityS5E03BasicInterglutealNumismatics Basic Intergluteal Numismatics]]" -- the caught Ass Crack Bandit (who drops quarters down people's ass cracks) turns out to be innocent of that crime, and the ending montage implies it could be one of several recurring characters, some of them having been involved with the investigation. The series finale virtually confirms it, pointing to Annie.

* In ''Literature/TheSecretOfTheChimneys'', M. Lemoine of the French police turns out to be King Victor, the international jewel thief, who has kidnapped the real Lemoine and is impersonating him.