A crime-solver in a PoliceProcedural who has killed and is TheAtoner because of this. Their method of atoning is to catch other criminals. Because they ''can'' think like criminals, they are often better at this than the average cop.

Interestingly, this motive even applies to people whose killing was perfectly legal--people who served in the military, the FBI, or a spy agency. It also applies to detectives whose killing, and thus whose need to atone for it, is ongoing.

A VampireDetectiveSeries is a supernatural version of this.

Compare RecruitingTheCriminal.

Beware if one of these has a FaceHeelTurn.
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!!Examples
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[[folder: Anime and Manga ]]

* Richard from ''Anime/{{Monster}}''.

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[[folder:Literature]]

* In the "Literature/FatherBrown" stories by Creator/GKChesterton, Father Brown (the series detective) meets and bests a thief named Flambeau, who, because he wants to atone for his crimes, then assists Father Brown in solving crimes by providing information about how professional criminals work.
* In Creator/LarryNiven's ''[[Literature/KnownSpace Gil the Arm]]'' stories, Gil Hamilton lost an arm in an accident in space. However, only prosthetics are available in space, as accidents in space tend to quickly ruin transplant stock and the minarchist Belters ''don't'' [[OrganTheft regularly execute "criminals" for their organs]]. He thus immigrates to Earth to take advantage of the UN-sponsored organ harvesting programme, justifying it to himself that his new arm would most likely come from an executed murderer(forgetting that an earlier Niven story had people broken up for ''running traffic lights''). Surprise - his brand-new limb came not from a villain, but from the seized stockpile of a ''criminal'' who [[NotSoDifferent killed people for their organs]]. Lacking the moral composure to have the arm removed, he joined the Amalgamated Regional Militia ([[MeaningfulName aka ARM]]), the agency which polices illegal body harvesting... but spends more time [[EnforcedTechnologyLevels suppressing inconvenient technologies]] and [[PopulationControl hunting illegal pregnancies]].
* In ''Literature/{{Discworld}}'', Commander Vimes has killed a ''lot'' of people, and even though they were mostly self-defence, he's aware that he wasn't really thinking about that when he killed them. He explicitly tells TheDragon in Discworld/{{Snuff}} that he recognised him as a killer the moment he saw him - because he's used to seeing a killer's face every day in his own mirror.
* Jerry Spinoza of J.R. Rain's ''The Vampire with the Dragon Tattoo'' became a private detective after his drinking led to the death of his son. He specializes in missing child cases in hopes of repaying his debt by saving the children of others.
* ''Literature/SkulduggeryPleasant'': It's never given as an explicit reason ''why'' he became a detective, but he does have a very dark past which includes [[spoiler: having once been exactly the sort of mass-murdering supervillain he now spends his days defeating]].

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[[folder: Live Action TV ]]

* Leroy Jethro Gibbs in ''Series/{{NCIS}}'' (Former Marine sniper) [[spoiler: Gibbs also killed his wife's and daughter's murderer.]]
* Mac Taylor in ''Series/{{CSINY}}'' (Former Marine)
* Seeley Booth in ''Series/{{Bones}}'' (Ex-sniper) He actually voiced this as his reasoning for joining the FBI.
** A supporting character on ''Bones'' was secretly working for a villain while he was doing the lab work to solve other crimes...
* Horatio Caine in ''Series/CSIMiami'' (Kinda) He tries to catch as many murderers as subject him to SuicideByCop. Preferably ''not'' by SuicideByCop.
* Ezekiel Stone of ''Series/{{Brimstone}}'' killed the man who raped his wife. When Ezekiel was later killed in the line of duty he was sent to Hell because, no matter how deserving of death the rapist had been, Stone's actions had been motivated by anger and the need for revenge instead of a desire for justice. The Devil sent him back to Earth to hunt down and return 113 escaped souls with the promise of a chance at entering Heaven (Not a guarantee, just the offering of a chance) if he captured all the escapees. Notably, Ezekiel has no personal regrets about what he did.
* He never really killed, but Sebastian Stark of ''Series/{{Shark}}'' was once a defense attorney . However, after one of his clients who he managed to get acquitted went on to kill his wife shortly after, Stark switched teams and becomes a prosecutor.
* Likewise, Patrick Jane of ''Series/TheMentalist'' didn't kill anyone, but his family was killed by a serial killer whom he'd offended with his fake psychic routine. Assisting the police is his way of making amends for this error, as well as his former career of conning people.
* The CowboyCop protagonist of the show ''Series/{{Maou}}'' became a detective out of guilt over having accidentally killed someone when he was younger (and having been let off scot-free because his rich and influential father pulled some strings).
* ''Series/{{Castle}}:'' [[spoiler:Captain Montgomery]] spent his career trying to atone for his actions as a rookie, when among other things he was complicit in [[spoiler: the death of Beckett's mother.]]
* In ''Series/BodyOfProof'', former neurosurgeon Megan Hunt is trying to atone for killing a patient on the table after neurological damage causes her hands to numb occasionally. She becomes a medical examiner because she can't kill anyone if they're already dead.

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[[folder: Video Game ]]

* The {{Suikoden}} series has [[spoiler: the Oboro Detective Agency in SuikodenV.]]
* A less severe example in ''VisualNovel/PhoenixWrightAceAttorney'' is Ron [=DeLite=], a former thief, opening a security business that helped other businesses defend themselves against thieves. [[spoiler: Of course the twist is that he then turns around and sells the plans to other thieves. At least his wife's in on it this time.]]
* ''LANoire'''s Cole Phelps was a Marine in the war. Specifically, he was TheNeidermeyer who [[spoiler:ended up leading an attack on Japanese civilians.]]
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[[folder: Real Life ]]

* Career con man Frank Abagnale, Jr. (on whose life the LeonardoDicaprio film Film/CatchMeIfYouCan was based) eventually settled down and became a high-profile securities consultant who specialized in the sort of crime he used to commit. It is also notable that to this day he has never taken money from law enforcement for his consultation, even refusing reimbursement for travel expenses.

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