History Main / MurderMakesYouCrazy

* Ed Nygma in ''Series/{{Gotham}}'' was initially [[AmbiguousDisorder decidedly eccentric]] and even a little creepy at times, but nothing worse than that. After a confrontation with his crush's [[DomesticAbuser abusive boyfriend]] ended in Ed stabbing the guy, he began showing signs of SanitySlippage.

->''"Killing... after a while it infects you, and once it does you're never rid of it."''
-->-- '''The Doctor''', ''Series/DoctorWho'', "The Doctor's Daughter"

* Ed Nygma in ''Series/{{Gotham}}'' was initially [[AmbiguousDisorder decidedly eccentric]] and even a little creepy at times, but nothing worse than that. After a confrontation with his crush's [[BastardBoyfriend abusive boyfriend]] ended in Ed stabbing the guy, he began showing signs of SanitySlippage.

%% Please see thread to discuss a new image.

[[quoteright:300:[[Manga/DeathNote https://static.tvtropes.org/pmwiki/pub/images/7558c03e_3dac_484d_baff_e77193831b9c.jpeg]]]]
[[caption-width-right:300:Top: Light Yagami as an OrdinaryHighSchoolStudent.\\
Bottom: Light Yagami after a 5-day killing spree.]]

* ''Series/BuffyTheVampireSlayer'''s[[spoiler: Faith]] starts to go off the deep end after she [[spoiler: kills a man who she thought was a vampire.]] Angel later tries to help her come around by establishing common ground. He calls the ability to kill without remorse the ultimate freedom, and a freedom that will drive anyone mad. And of course [[AxCrazy he's talking from experience]].

[[quoteright:300::https://static.tvtropes.org/pmwiki/pub/images/7558c03e_3dac_484d_baff_e77193831b9c.jpeg]]

Usually, this involves some lead-up event where they are sane but [[GainingTheWillToKill have decided to kill]] from being put into a situation where, unless they are an ActualPacifist with a knack for [[TakeAThirdOption taking third options]], they will practically be forced to murder [[SadisticChoice because of a no-win situation]]. After doing the actual murder, however, the act makes them evil, or in [[MurderMakesYouCrazy this trope]], insane.

Bottom: Light Yagami after a 5-day killing spree]].

[[caption-width-right:300:Top: Light Yagami as an OrdinaryHighSchoolStudent Bottom: Light Yagami after a killing spree 5 days later]].

[[caption-width-right:300:Top: Light Yagami as an OrdinaryHighSchoolStudent
Bottom: Light Yagami after a killing spree 5 days later]].

* More than one writer has cited this trope as a reason behind Franchise/{{Batman}}'s TechnicalPacifist stance. He fears he is so close to the ragged edge of sanity already that if he starts killing ''anyone'', [[NotSoDifferent he will not be able to stop]]. In one alternate universe shown in ''Comicbook/CountdownToFinalCrisis'', he kills ComicBook/TheJoker and then decides he might as well kill ''every other supervillain'' -- and succeeds.

* Both Theatre/{{Macbeth}} and his wife have this happen to them after their murder of Duncan.

!Examples:

[[folder: Anime and Manga ]]

[[folder: Comic Books ]]

[[folder: Film ]]

[[folder: Literature ]]

[[folder: Live-Action TV]]

[[folder: Tabletop Games ]]

[[folder: Video Games ]]

[[folder: Visual Novels]]

[[/folder]]

* ''VisualNovel/HigurashiWhenTheyCry'': [[spoiler:Keiichi and Rena, after killing Teppei and Rina, respectively. Shion's first kill was actually an accident, since she wanted to interrogate Oryou about Satoshi. Afterwards, she realizes there's no turning back now. Ironically, she might have convinced Shion had she survived, because Mion admitted that she herself nearly killed her grandmother in anger after Satoshi disappeared but Oryou managed to convince her that the Sonozakis were innocent.]]

* ''VisualNovel/HigurashiWhenTheyCry'': [[spoiler:Keiichi and Rena, after killing Teppei and Rina, respectively.]]

* Light Yagami of ''Manga/DeathNote''. He's an [[OrdinaryHighSchoolStudent ordinary school student]] until he writes the first name in the titular ArtifactOfDoom. After that, he develops [[AGodAmI delusions of grandeur]] and wants to cleanse the world of evil (leaving himself as the only evil person, as Ryuuk points out). In the manga, the reader first sees how Light has already killed numerous targets before flashing back to his first kill for maximum shock value and to show how far he has already fallen in such a short time.

The difference between this and a normal FaceHeelTurn, is that this usually follows [[BreakTheCutie excessive amounts of guilt and gloom]], and results not in evil, but rather madness. Still, it can probably be viewed as a sister trope. Likewise for SlowlySlippingIntoEvil, since it isn't evil you slip into, but rather madness.

----

* In the Post-Crisis universe, ''ComicBook/{{Superman}}'' is forced to kill three Kryptonian criminals that wiped out an alternate version of Earth. Since there are no longer any officials to sentence them on their world, no legal precedent that would let them be imprisoned in his world, and they have already vowed to find some way to regain their powers and go after him in revenge, Superman appoints himself JudgeJuryAndExecutioner and uses kryptonite (immune to it himself as this was kryptonite from a different universe) to kill them. Superman was later so emotionally disturbed about this that he developed a SplitPersonality that took the form of an extreme NinetiesAntiHero, temporarily abandoning Earth until he was helped to see that he only sinned in the cause of justice under extreme circumstances.

-->'''Ash:''' ''(Talking to mirror)'' I'm fine...I'm fine...

* ''Series/BuffyTheVampireSlayer'''s[[spoiler: Faith]] starts to go off the deep end after she [[spoiler: kills a man who she thought was a vampire.]] Angel later tries to help her come around by establishing common ground. He calls the ability to kill without remorse the ultimate freedom, and a freedom that will drive anyone mad. And of course [[AxCrazy he's taking from experience]].

* Both ''Theatre/{{Macbeth}}'' and his wife have this happen to them after their murder of Duncan.

* Every time you kill someone in ''VideoGame/YandereSimulator'', you lose Sanity. Lose too much Sanity without an effort to regain it, and people won't want to deal with you -- least of all Senpai. This only partially fits the trope, since by WordOfGod Yandere-chan was ''already'' insane. The 'Sanity' meter just tracks how well she can keep on her MaskOfSanity.

-->-- '''[[Series/DoctorWho The Doctor]]''' in "The Doctor's Daughter."

Normally, in RealLife (although there may be exceptions), a person is ''already'' crazy and/or violent before they contemplate murder. In television, however, circumstances will cause you to commit murder, and then you keep killing. No, this trope is '''not''' about [[NeverOneMurder murder where you have to keep killing in order to "hide the evidence"]]. Instead, it's about murder ''actually warping the mind'', either by [[MyGodWhatHaveIDone guilt]] or as the [[NeverMyFault process of rationalizing the murder]] sets in. (Unless, of course, [[TheSociopath it never bothered you in the first place.]])

Normally, in RealLife (although there may be exceptions), a person is ''already'' crazy and/or violent before they contemplate murder. In television, however, circumstances will cause you to commit murder, and then you keep killing. No, this trope is '''not''' about [[NeverOneMurder murder where you have to keep killing in order to "hide the evidence"]]. Instead, it's about murder ''actually warping the mind'', either by [[MyGodWhatHaveIDone guilt]] or as the [[NeverMyFault process of rationalizing the murder]] sets in.

[[folder: Literature ]]
* Used in ''Literature/TheDresdenFiles'' and the reason for the First Rule -- magic is an expression of will given form, so using it to kill someone is particularly warping and even addictive. Non-magical killing doesn't cause this, though Harry confesses in one book that he's haunted by having to execute two people, and fears that this makes him a monster as well.

* Creator/AgathaChristie's Literature/HerculePoirot discusses this trope a few times. He notes that [[GainingTheWillToKill once someone gets over the initial mental hurdle of taking someone's life for the first time]], [[ItGetsEasier to them]] [[MurderIsTheBestSolution murder becomes an acceptable solution to any number of life problems]]. This becomes particularly explicit in the final Poirot novel, ''Curtain''; [[spoiler:faced with a man who has manipulated others into killing for him without ever actually committing a single crime himself, Poirot chooses to kill the man himself, and then it is strongly implied that Poirot let himself die of his current heart condition so that he wouldn't succumb to this fate and start believing that he had the right to kill those he deemed it necessary to eliminate]].
* In the ''Literature/HarryPotter'' series, committing murder ''tears the soul''. The soul can heal from this, provided both pieces are left next to each other. However, Dark wizards have been known to exploit this soul-tearing by using it to make [[SoulJar Horcruxes]].
* Falkland’s life goes decidedly downhill after he murders Tyrrel in ''Literature/CalebWilliams''. He goes from being the most popular squire in his county to a man who avoids even his servants, and goes wandering at night in stormy weather.

[[folder: Tabletop Games ]]
* ''TabletopGame/WorldOfDarkness'': Due to the way [[KarmaMeter Morality system]] is designed, this trope is almost unavoidable. When you murder someone, your psyche cracks a bit and make it easier the next time you have/want to do it again. Do this often enough, and you turn into a Hollywood-style psycho, known as [[TabletopGame/HunterTheVigil a Slasher]].
[[/folder]]

* Every time you kill someone in ''VideoGame/YandereSimulator'', you lose Sanity. Lose too much Sanity without an effort to regain it, and people won't want to deal with you -- least of all Senpai. [=YandereDev=] has stated, however, that Yandere-chan is ''already'' insane, and that the Sanity Meter just shows how well she is hiding that fact.

* In the Post-Crisis universe, ''ComicBook/{{Superman}}'' is forced to kill three Kryptonian criminals that wiped out an alternate version of Earth. Since there are no longer any officials to sentence them, Superman appoints himself JudgeJuryAndExecutioner and uses kryptonite (keeping himself in a KryptoniteProofSuit of course) to kill them. Superman was later so emotionally disturbed about this that he developed a SplitPersonality that took the form of an extreme NinetiesAntiHero.

* Creator/AgathaChristie's Literature/HerculePoirot discusses this trope a few times. He notes that [[GainingTheWillToKill once someone gets over the initial mental hurdle of taking someone's life for the first time]], [[ItGetsEasier to them]] [[MurderIsTheBestSolution murder becomes an acceptable solution to any number of life problems]].

* ''HigurashiWhenTheyCry'': [[spoiler:Keiichi and Rena, after killing Teppei and Rina, respectively.]]

* HigurashiWhenTheyCry: [[spoiler:Keiichi and Rena, after killing Teppei and Rina, respectively.]]