The perp hires a detective to solve the crime, in order to throw suspicion off himself. The perp may have a plan to make the detective a Fall Guy for the crime. Or it may be done merely to strengthen their claim that they're innocent and ignorant of the crime (the same logic that sometimes leads criminals to report their own crimes to the police). Typically, the detective in question is a Defective Detective, to minimize the odds of him actually working it out.
Invariably, the detective turns out to be not quite so defective as the perp thought, and figures it all out.
This often leads to monologuing (both from the Detective and the Perp) and the inevitable "The only thing I couldn't figure out was..." statement during the Final Confrontation.
This is an archetypal trope in detective fiction, as even Sherlock Holmes was abused like this.
This trope is often used as a reveal or twist, expect spoilers below.
- In StrikerS Sound Stage X of the Lyrical Nanoha franchise, Teana found herself in this role, as she eventually found out that the perp who was behind the killings of the case she was investigating was Runessa, her assistant who had been part of the case since day one and who regarded the already dead fanatic Toredia as a mentor and father figure.
- In Detective Conan, a case that had both Conan and Heiji working together in Osaka had the detective who was helping them and Kogoro to catch a serial killer... as the killer himself. The victims were the people who caused the death of his father, 25 years ago; he specifically became a policeman to find them, make them spit the truth out, and then kill them in a way that would both baffle the whole Osaka police corps ''and'' let him blame someone else for it.
- In The Firesign Theatre's "The Further Adventures of Nick Danger", Nancy claims to need Nick's help, but really, she just wants a patsy to frame for the murder of Rocky Roccoco, who is blackmailing her.
- In the Sherlock Holmes (BBC Radio) radio play "The Case of the Determined Client," the client tampers with a crime scene to make it look as though her father had been murdered outright, rather than starting the fight with the man who killed him. When the police don't even notice her hints, she calls in Sherlock Holmes, who naturally sees not only the evidence she'd left but that she was the one who left it. She ruefully admits that she should have known better.
- Randall Banticoff does this to Luke Cage in Luke Cage Noir, hiring Cage to investigate his wife's murder while arranging for him to take the rap for the crime - and die before a trial could potentially expose it as a frame job.
- Taken to the extreme in Sin City where Ava Lord hires private eye Dwight McCarthy to get evidence on her supposedly abusive husband who may be plotting to kill her. It ends up being a setup; she manipulates Dwight into killing her husband himself.
- Parodied in the Sam Spayed: Babes and Bullets section of Garfield: His 9 Lives, in which Spayed immediately assumes his client killed her husband and is planning to double-cross him, he's just not sure why and how. (She didn't.)
- Happens to Jake Gittes at the start of Chinatown.
- In the movie Ace Ventura: When Nature Calls, Ace is hired by an Englishman trying to harvest bat guano for fertilizer, who has to start a genocidal war between local African tribes to get it. Ace was hired as a means of establishing for the public that he had done everything he could to prevent the war. When Ace unexpectedly figures out who is behind the scheme to wipe out the innocent tribe, the Englishman decides to change his plans and set Ace up as a patsy for the whole thing.
- Lois Einhorn did much the same thing in the original Ace Ventura: Pet Detective, trying to frame Ace for her own murder of Roger Podacter and kidnapping of Snowflake and Dan Marino.
- The 1987 thriller No Way Out subverts this: Commander Tom Farrell, the man that Defense Secretary David Brice and his aide Scott Pritchard hire to investigate a murder that they are attempting to blame on a Soviet mole is the person they are trying to frame and knows that Brice is the one actually guilty of the murder.
- Nero Wolfe once required a client to sign a statement promising to pay in full, even if he turned out to be the guilty one. It turned out to be a good precaution.
- Writer Ross Macdonald's characters, particularly Lew Archer, were picked so often for plots like this, it's hardly any wonder that they always demanded payment in advance.
- Ur-Example is probably the Sherlock Holmes story The Adventure of the Retired Colourman. A quote from the end of the story:
"You certainly seem to have met every difficulty," said the inspector. "Of course, he was bound to call us in, but why he should have gone to you I can't understand."
"Pure swank!" Holmes answered. "He felt so clever and so sure of himself that he imagined no one could touch him. He could say to any suspicious neighbour, 'Look at the steps I have taken. I have consulted not only the police but even Sherlock Holmes.'"
- Who Censored Roger Rabbit?: Roger hired Eddie Valiant to investigate his boss - so that Roger would have someone to frame when he killed his boss. In the final chapter Eddie admits that the plan would have worked were it not for two complications that Roger had no way of seeing coming.
- Happens to young and unexperienced Bert Kling in 87th Precinct novel The Muggler.
- The Cuckoo's Calling: John Bristow hired Cormoran Strike to investigate his stepsister's death, in the hopes of deflecting suspicion from himself.
- In the first Sister Fidelma story, "The High King's Sword", the abbot is encouraged to request Fidelma by the criminals, who realise that unless a clever and scrupulous dalaigh is involved, one of them will be condemned as the most likely suspect without anyone really investigating enough to find their carefully planted frame-up.
- In Anthony Berkeley's The Piccadilly Murder, Mr Chitterwick, the detective, is the key witness in the prosecution of a man for murder. The accused man's friends and wife urge Mr Chitterwick to investigate more thoroughly, saying they're sure there's been a miscarriage of justice. The friends are genuine; the wife is the real killer. She only meant to reinforce Mr Chitterwick's determination to do his public duty and convict her husband. But she overdoes her pleading, he agrees to investigate, and the whole truth comes out.
- The Rockford Files seemed to do this a lot, but all shows about private detectives will do one eventually.
- Usually not applicable to police, but Columbo caught one once, when the murderer was the commissioner. He specifically requested Columbo for the case, having somehow failed to notice that the "bumbling" detective had a nearly spotless track record, having only failed to close one case in his entire decades-long career.
- Another police example is the CSI fourth season episode Suckers where a casino owner attempts to fake a huge robbery for the insurance money.
- In an episode of Poirot, a shifty old lady tried to abuse Capt. Hastings in this way; she had the sense not to go to Poirot directly. In the books, however, Poirot frequently finds himself working for clients with something to hide — though not necessarily murder.
- Monk: In "Mr. Monk and the Leper," Monk is hired by a man who introduces himself as Derek Bronson, who has been missing for seven years and will soon be declared legally dead at a probate hearing. He has Monk and Natalie break into his house to retrieve some letters, and while they're doing so, they are caught by Mandy Bronson, Derek's wife. Monk then attends a probate hearing where he testifies and validates Mandy's story that Derek is alive. All is well....until Monk sees Julie trying to open a bottle of ketchup and she comments, "Who would need ketchup in 1840?" causing Monk to realize that he's been duped, because the security panel in Derek's house had the words "Founded 2003" on it (the episode was aired in 2006), so he wonders how Derek could know his own house security code for a system installed after he had vanished. He concludes that seven years ago, Mandy murdered her husband, then got rid of the body and lived off his money, aware that when he was officially declared dead, she'd lose his house, so she hired an acquaintance - a professional pianist - and seduced him to impersonate Derek, and they brought Monk in as a "witness" because they knew that if he thought Derek was a leper, he'd never want to take a good look at the man (further helped by making the meetings happen in dimly lit locations). Monk and Natalie then discover that Mandy has shot and killed the accomplice and is planning to get rid of his body in the same way she got rid of her husband's.
- Happens so frequently in Jonathan Creek that merely soliciting his services should be ample proof of guilt. The episode "Daemon's Roost" is a big one, because he didn't figure it out; there's a Flash Back to the Striped Unicorn case, in which a man carefully stages his wife's murder so that it initially appears as if only he could have done it, but there's a brilliant explanation otherwise for Jonathan to find. Jonathan only realises the truth after the man's second wife calls him in on another case, six years later.
- Lampshaded in Dark Justice: a not-so-bright gigolo and his girlfriend hire a female detective to solve the murder of the rich woman he was living off. The detective easily proves it was these two who did the deed, and asks why she was hired. The gigolo says he thought no-one would suspect him if he did.
Detective: It was done in Jagged Edge!Girlfriend (to gigolo boyfriend): I wanted to see that movie, but you said no!
- A weird one in Murder, She Wrote: The murderer is a DA, who killed one of the defendants in a major fraud case. Earlier, he tried to phone her and accidentally called Jessica's number. To cover this up, the DA subpeonas Jessica and refuses to believe she has no idea what it's about. So Jessica has to solve the murder to avoid being found in contempt of court.
- In Sledge Hammer!: the episode "Play It Again, Sledge" has a women hire Sledge as private investigator, to make him an eyewitness of her "self-defence" murder.
- Cold Case had an interesting variation: A professor was accused, but never proven guilty, of the murder of one of his female students. Because of this he was discredited and fired by the university. He went to the team to have them reopen the case, only for them to figure out was him all along, and this time they gathered enough evidence to arrest and convict him. Oops.
- An episode of Simon & Simon deals with the detectives being hired by a magician into a case, and they discover that the ex wife of the magician did it. Later, they discover it was all the magician ruse. Then he explains:
So it was just like a standard Stage Magician trick: You guys are the public, you must be smart enough to figure out the distraction, but not smart enough to discover the real trick.
- Murdoch Mysteries
- A convoluted one in the episode "Murdoch Appreciation Society". The killer wants to frame the professor who expelled him from medical school for the murder of a man who's donated his brain to science. But he knows that if the death doesn't look suspicious, the corpse will go straight to the professor and there won't be a proper post mortem. On the other hand, if it does look like an obvious murder, Murdoch will realise the professor is being framed. So he joins the eponymous Appreciation Society and convinces them to stage a fake murder so they can watch Murdoch work, using a body he can steal from the medical school. So not only does Murdoch get involved but there's an extra layer of false explanation (the fake murder) for him to disprove, and it looks like the professor would have committed a perfect crime except for the Society's interference.
- Invoked Trope in "A Study in Pink": When evidence is mounting that Murdoch's childhood friend, the private detective Freddie Pink might be a murderer, she protests that she's the one who called the police. He suggests she might be attempting this, and she says she'd surely know his methods well enough to anticipate him seeing through it, unless he thinks she was anticipating him concluding that she wouldn't do it because he'd see through it... It turns out there was no murder, although Freddie was protecting a client who had killed her husband in self-defence, and had been framed by his family so she'd be forced to explain things in court.
- In the Elementary episode "The Visions of Norman P. Horowitz", Sherlock is contacted by Horowitz's brother, not to investigate his death by accidental overdose, but because before he died he predicted a series of deaths that is coming true, and Sherlock is on the list. Sherlock naturally feels he has to prove Horowitz could not predict the future, and someone killed these people to make it look as if he could. It was the brother, and the whole point of the exercise was to draw the attention of former Holmes client (and vague associate of Horrowitz} Henry Baskerville, so he'd pay silly money for the rest of Horowitz's "predictions".
- Parodied in one of the "Tracer Bullet" strips of Calvin and Hobbes. In Calvin's fantasies, he's being used as the fall-guy for a room being ransacked; in real life, Calvin was at least partially responsible (and may have been entirely responsible depending on whether you think Hobbes is alive).
- Parodied in the Noir Episode of John Finnemore's Souvenir Programme, in which Finnemore is hired by a Femme Fatale in what turns out to be just one step of an overly-complicated and self-contradictory cover-up by a Sidney Greenstreet type who, it eventually transpires, has neglected to actually commit a crime first.
- Amateur Adventure Game example: the AGS adventure game Murder in a Wheel features a freelance detective who has to solve the murder of a pet hamster only to find himself in this situation.
- Ace Attorney had a lawyer patsy: in case 2 of Apollo Justice, the title character is hired by the guilty party to help the innocent defendant, because the flyers for Apollo's practice made him seem likely to be incompetent.
- Non-detective variation: In Metal Gear Solid 2: Sons of Liberty, Olga is first seen in the Plant Chapter contacting Solidus by radio, alerting him to the presence of "a ninja." Much later, it is revealed that she's the ninja.
- In the third chapter of Limbo of the Lost, after being wrongfully accused of stealing souls, Briggs is accounted for by collector O'Negus, freed, and appointed detective by the mayor to determine who is actually stealing the souls. It turns out that the soul taker is posing as the mayor, and O'Negus is one of his accomplices.
- In Jack Orlando, it looks like Orlando is lucky to be allowed to try to prove his own innocence, but since the Inspector is actually in on the crime, Orlando isn't meant to get anywhere. Part way through the game, Orlando gets in trouble again and is told to wait for the Inspector - but if he does, the Inspector decides that he's making too much progress and locks him up, resulting in a Nonstandard Game Over.
- Occurs in Nancy Drew: The Deadly Device; believing Nancy Drew to be less-than-competent, the murderer hires her to investigate the death of a scientist.
- Black Jack Justice:
- "Justice is Blind" has Jack and Trixie hired by a man as incognito security at a showing of his family's heirloom jewelry. In the course of the episode no less than three notorious thieves show up at the event and, when the jewels go missing, they're immediately suspected. The only problem is that one had gone straight, another was scoping out the artwork in another room, and Jack managed to nab the third when the lights went out, ensuring he couldn't have done anything. The whole thing turns out to have been a plot by their client to steal the gems himself for the money, while one of the real thieves was set up for the crime.
- "The Reunion" features a woman, Edie, hiring the detectives to help facilitate a reunion with her estranged twin sister, Jane. The patsy comes in when it's revealed that Edie is Jane. Jane murdered Edie in the heat of the moment and tried to pretend to make up, with Jack and Trixie as witnesses, so that she wouldn't be suspected when Evie was missed. Small inconsistencies in the situation trigger Jack's radar, making him suspicious throughout until he's able to confirm the truth while confronting Jane.
- "The Do-Nothing Detectives" features a man named Raymond Davis giving Jack and Trixie $1,000 to cease working for their client Angela Barnes... who neither of them had ever actually met. The odd behavior is explained by the idea that Jack and Trixie would be witnesses when Angela Barnes turned up dead by suicide after apparently murdering their client. The man who hired them killed by Angela Barnes and the real Raymond Davis, making sure to mess up the man's face so he couldn't be readily identified as not the man Jack and Trixie met. The whole thing falls apart because the whole situation is so suspicious Jack just has to investigate it despite their job literally being to do no such thing.
- Scooby-Doo featured this something like every second episode, and so did the movie (notably Scooby-Doo! and the Witch's Ghost).
- Used in the two part Batman Beyond episode "The Call." Superman asks for Batman's help uncovering a traitor in the JLU. Guess who the traitor is?
- Inverted in the Foster's Home for Imaginary Friends episode "Jackie Khones and the Case of the Overdue Library Book", when Mac hires Jackie Khones to find out who stole his library card to check out a book that has since become overdue. The culprit? Jackie.
- In the Dog City episode "The Great Dane Curse", Candice Dane hired Ace to find out who's trying to kill her, and then disappeared, leaving Ace as the prime suspect in her murder. It eventually transpires that she faked her death to escape her controlling father.