[[quoteright:308:[[Film/ManiacCop http://static.tvtropes.org/pmwiki/pub/images/MC_952.jpg]]]]

->''"The cop's the killer!"''
-->-- '''Brian''' in ''PsychoCopReturns'' (and probably everyone else on this page)

A member of law enforcement who also engages in murder. This person's motivations may range anywhere from [[ProfessionalKiller monetary gain]] to [[VigilanteMan exacting a form of street justice]]. Either way, expect this person to be much more dangerous than your average killer.

Note that despite the name, the Killer Cop isn't always an actual police officer. He (or she) may also be a civilian employee, such as a forensics expert or something. Also, if the Killer Cop ''is'' an officer, their murders are obviously committed for a reason other than to maintain a cover identity. (Well, at least one hopes an undercover officer doesn't go to those lengths.)

If the Killer Cop is a SerialKiller, the observant viewer may recognize the following signs:

# The crime scenes are jarringly devoid of any incriminating evidence. Either the killer is a forensics expert and cleaned up so thoroughly that they got rid of the evidence or they are a savvy police officer who has investigated many crime scenes and knows how to avoid leaving evidence in the first place. Note: This is not always a given, as a SerialKiller who ''isn't'' a member of law enforcement can avoid leaving evidence as well.
# If the killer is suspected to be copying the methods of another killer, the copy will be exactly like the original, even down the details that only a member of law enforcement would know.
# If the killer is attempting to [[{{Frameup}} frame someone else]] for their crimes, the frame-up will be suspiciously thorough. The amount of evidence against the person will likely lead the viewer to two conclusions:
## That a calculating TV SerialKiller wouldn't be stupid enough to leave that much evidence against themselves, meaning the suspect isn't the killer and
## The ''real'' killer has such intimate knowledge of evidence and police work that they must be a member of law enforcement. Like the first sign, this isn't a given, as it is possible to research forensics.

In Crime Dramas, this may be used as a TwistEnding, especially [[TheKillerInMe if the cop is the protagonist]].

See also DetectiveMole. The inverse of a CopKiller, although the two tropes sometimes overlap.

'''Note:''' A character can qualify for this even if they don't use their position or expertise to help with their murders. However, if they appear in a murder mystery, they probably will.

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!!Examples:

[[foldercontrol]]

[[folder:Anime/Manga]]
* [[AGodAmI Light Yagami]], the protagonist of ''Manga/DeathNote'', joins the police force specifically to work on the investigation of his own murders, and get close enough to kill the SympatheticInspectorAntagonist trying to catch him. It doesn't work so well the first time he tries, [[spoiler:but the second attempt is [[AntagonistInMourning much better]]]].
[[/folder]]

[[folder:Comicbooks]]
* [[VigilanteMan Americop]] from ''CaptainAmerica''.
* In ''ComicBook/GothamCentral'', DirtyCop Jim Corrigan ultimately became this, murdering Crispus Allen.
* Wilson Priest, one of the judges featured in ''JudgeDredd'''s ''The Pit'' arc is this. He murders a suspect after he repeatedly gets OffOnATechnicality and begins to do it more often.
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[[folder:Film]]
* The eponymous characters of the ''Film/ManiacCop'' and ''Film/PsychoCop'' films.
* [[spoiler:AlPacino]] in ''RighteousKill''.
* Jim Belushi's character in the movie ''GangRelated''. He uses guns already tagged as evidence in other crimes to rob and kill drug dealers. Ironically, the one character he doesn't kill is his partner, played by Tupac Shakur.
* The vigilante cops from the ''Dirty Harry'' sequel ''MagnumForce''.
* ''StrangeDays''
* The killer in ''Bloody Murder 2: Closing Camp'' turns out to be the sheriff, who is really the father of the thought legendary camp boogeyman, Trevor Moorehouse.
* In ''Holla If You Hear Me'', it's revealed there's three killers, [[SiblingsInCrime two brothers and one sister]]. One of the brothers is a detective.
* ''Film/TheProwler'' turns out to be [[spoiler:Sheriff George Fraser]].
* The Australian thriller ''Dangerous Game''. Notably, the officer (while obviously unhinged) only killed by accident, and feels extremely conflicted about trying to murder the witnesses.
* ''Film/{{Mindhunters}}''. After searching the entire island with infrared sensors, the FBI trainees rule out anyone else being on the island, and realize the killer is one of their own.
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[[folder:Literature]]
* Robert Crais seems to like these: In ''L.A. Requiem'', the killer who was framing Joe Pike turned out to be [[spoiler:the guy who pushed the mail cart at police headquarters.]] In ''Demolition Angel'', the person who murdered Charlie Riggio was [[spoiler:his own partner on the Bomb Squad, Buck Daggett.]] In ''The Two Minute Rule'', the man who murdered the four officers was [[spoiler:William Cecil of the FBI Bank Squad.]]
* The protagonist from JimThompson's novel ''The Killer Inside Me''.
* [[spoiler:The FBI Agent Denton and his cohorts]] in ''[[Literature/TheDresdenFiles Fool Moon]].''
* [[spoiler:Frank Ennunzio, FBI Forensic Linguist]] in Lisa Gardner's novel, ''The Killing Hour''.
* In the Creator/TomClancy novel ''[[Literature/JackRyan Without Remorse]]'', a CorruptCop murders a drug dealer that his (criminal) boss suspected of being a security risk. He even manages to do it in a way that causes multiple witnesses - police officers themselves - to honestly believe that the victim was shot in self-defense when he attempted to resist arrest.
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[[folder:Live-Action TV]]
* ''WalkerTexasRanger'': A 1997 episode "The Brotherhood" featured cops who frustrated by the system kill suspects before they've had their due process, and it results in an innocent man paying with his life after he had been wrongly accused of rape.
* ''TheDukesOfHazzard'': The final season's "Cool Hands, Luke and Bo" has police officers who it is strongly implied have killed inmates in the past at the Osage Road Prison, where Bo, Luke, Rosco, and Boss Hogg are being held on false charges.
* ''Series/LawAndOrder'' and its various spin-offs have featured these on more than one occasion.
* ''RizzoliAndIsles'' had a detective who killed a bunch of women with the same names as the original Boston Strangler victims. His purpose in so doing was to [[FramingTheGuiltyParty frame the person he believed was really the Boston Strangler]]. He had worked the original murder case and didn't believe that the person who confessed was really the killer.
* Of course, the titular protagonist of ''Series/{{Dexter}}'' is one of these. He also went after one in season four, a cop who'd killed her own husband and daughter and made it look like a robbery gone foul. She was a particularly hard target because her experience allowed her to suspect Dexter was up to something pretty early on.
* ''Series/{{CSI}}'':
** Paul Millander, the bathtub killer, is revealed to have a double life as [[spoiler:a judge]].
** Ray Langston, at the end of season 11. Not a cop, but still a CSI.
* ''{{CSI NY}}'' had one of those, a cop that went [[DirtyCop dirty]] and murdered others to cover his tracks.
* ''Series/CriminalMinds'':
** The first episode that features The Reaper leads you to think that this might be the case. The Reaper was a serial killer who had stopped killing for ten years, then started killing again. In the original run of murders, he had killed a bunch of people, but left one victim alive. Ten years later, that victim was hiding from The Reaper by living at a number of different addresses and switching between them. At one of The Reaper's crime scenes, he left the victim's address numbers written on windows in blood, leading you to think that the lead detective from the local police department might be The Reaper. (Since he would've been one of the few people who knew the addresses, as they had been told to him by the victim.) However, [[AvertedTrope this turns out not to be the case.]] In reality, [[spoiler:the "victim" survived because he was The Reaper]].
** Another episode features a cop that stages shootings so he can be the first to "save" the victim. Occasionally those victims die, but he is honored as a hero cop. He tries to kill [[spoiler:Peneloppe when he thinks she is on to him]].
** In "Broken Mirror", it turns out one of the local FBI agents helping with the investigation is the perp, while "A Rite of Passage" has a Sheriff's Deputy turn out to be "Santa Muerte".
* On ''{{Bones}}'', serial kidnapper (and also killer) The Gravedigger turned out to be [[spoiler:United States Attorney and former FBI agent Heather Taffet]], and chose self-representation during the trial.
** Also Agent Kenton in "Two Bodies In The Lab".
* On ''{{Frasier}}'' in ThatOneCase that Martin has been working on for years, it turns out that the detective did it.
* One of the 1970s-era ''Series/{{Columbo}}'' mysteries involved the Police Commissioner himself trying to get away with committing murder.
* A recurring villain on ''Series/ColdCase'' was a serial killer who worked as a civilian in the police department's records division, and used what he knew about the detectives to successfully deflect their interrogation techniques.
* In an episode of ''Series/BeyondBeliefFactOrFiction'', the protagonist of one story is a cop who discovers that [[TheKillerInMe he killed a young woman while sleepwalking.]] He is completely unaware of this until he compares the bullet found at the scene to one in his gun.
* An episode of ''Series/{{Angel}}'' featured a police captain suppressing crime in his district by raising recently deceased police officers as zombies and having them indiscriminately and violently harass people on the streets after dark. They end up committing several murders themselves.
* [[spoiler:Detective Rick Messer, aka The Bearded Man]] in ''{{Series/Damages}}'', [[spoiler:who acts as a hit man for a CorruptCorporateExecutive]]. Plays with this as it isn't revealed that he's a cop until late on.
* Manny Lopez in the ''Series/MacGyver'' episode "Tough Boys".
* A subplot of ''QueerAsFolk'' has Debbie finding the body of a strangled prostitute in a dumpster. The investigation is suspended because of "lack of evidence" before the police can even identify the victim, and he becomes known simply as "Dumpster Boy". Later, it turns out that the killer was a cop who frequently solicited male prostitutes, and the reason the investigation was shut down so quickly was because the killer, in a state of panic after having committed a [[IDidntMeanToKillHim murder by mistake]], goes to his [[ScrewTheRulesIHaveConnections ex-partner and long-time friend]], [[CorruptPolitician Police Chief]] Stockwell, and begs for help.
* The killer in ''Series/BronBroen'' turns out to be an embittered ex-cop, foreshadowed by his knowledge of police procedure and access to uniforms.
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[[folder:Video Games]]
* [[spoiler:Detective Adachi]] from ''VideoGame/{{Persona 4}}'' qualifies as one of these. Bonus points for the supernatural powers that helped him avoid leaving evidence.
** In ''VideoGame/DevilSurvivor'', [[spoiler:a few rogue cops abuse their position and their possession of [=COMPs=] to kill innocent bystanders with demons.]]
* In the AdventureGame ''LauraBow 2: The Dagger of Amon Ra'', the killer turns out to be [[spoiler:Ryan O'Reily, the detective working on the case]].
* Kurtis Stryker of the ''MortalKombat'' series.
* Case 1-5 of ''Franchise/AceAttorney'' has former detective and current high prosecutor Lana Skye accused of murder. The real killer is [[spoiler:not just a killer cop, but a killer police chief.]]
** Not to mention killer [[spoiler:prosecutors Manfred von Karma and Godot and Jacques Portsman]] and killer [[spoiler:defense attorneys Calisto Yew and Kristoph Gavin.]]
** And as of Dual Destinies, [[spoiler:detective Bobby Fulbright, who is actually TheMole, and not even a real detective.]]
* In ''VideoGame/HeavyRain'', it's eventually discovered that [[spoiler:[[SerialKiller the Origami Killer]] is a retired police officer. Specifically, [[DetectiveMole Scott Shelby]].]]

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[[folder:Web Originals]]
* SMBC theater's [[http://www.youtube.com/watch?v=bMxds0dBILc Homicide Detective]].
* [[http://www.scp-wiki.net/scp-973 SCP-973]], an unstoppable, homicidal traffic cop.
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[[folder:Webcomics]]
* ''WebComic/AxeCop''. He'll [[CatchPhrase chop your head off!]]
* Played with in [[http://www.smbc-comics.com/index.php?db=comics&id=1860 SMBC]].
[[/folder]]

[[folder:Real Life]]
* Happens way too often in real life, unfortunately. A lot of police officers ''aren't even charged'' with murders committed while on-duty.
* There was a case once where the murderer turned out to be one of the cops working on the case. This was discovered after a visual reconstruction of the offender was created.
* There has been speculation that the [[http://en.wikipedia.org/wiki/Long_Island_serial_killer Long Island serial killer]] is someone working for law enforcement.
* Serial killers [[http://en.wikipedia.org/wiki/Gerard_John_Schaefer Gerard Schaefer]] and [[http://en.wikipedia.org/wiki/Norbert_Poehlke Norbert Poehlke]].
** Spree killer [[http://en.wikipedia.org/wiki/Tore_Hedin Tore Hedin]]
* [[http://www.huffingtonpost.com/2012/12/11/manuel-pardo-executed-last-meal_n_2279613.html Manuel Pardo]] of Florida. Some say Dexter was inspired by him.
* Woo Bum-kon, who was, for awhile, the most prolific murderer in a single day. He killed 54 people one day in 1982 in South Korea, and then blew himself up, along with his two final victims.
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