The last defense of the Obviously Evil and the Villain with Good Publicity. Cornered like a rat in a trap with a perfect summary of their misdeeds, the guilty party dispenses with pretenses. Whatever they seemed like before has fallen away, and you get to see what they are Beneath the Mask. They may have thought they had accomplished The Perfect Crime, but having heard it summed up to them, they issue a challenge — that the pretty little story they just listened to actually have one scrap of evidence.
This is, naturally, the chief conflict of the moment, and demands a response. Do we have the necessary evidence to succeed, and will we present it as the icing on our cake, or do We Need to Get Proof? Be careful to ensure the significance of your evidence, lest you end up with the villain's guilt Not Proven.
A favorite of the mystery genre, especially as one last challenge for the detective to overcome, but may also show up in police procedurals or even less likely places. Of course, the Genre Savvy will know that anyone who says this is not the Red Herring, as it's something only a guilty party would say.
Be mindful, the examples below contain unmarked spoilers.
- In A Serious Man, student Clive Park bribes his teacher for a better grade, but Prof. Larry Gopnik refuses to take it. But when he tries to confront Clive's father about the incident, his father instead tells him he'll sue Larry for defamation unless he takes the bribe. It's extremely obvious he and Clive left it, yet they urge him to just "accept the mystery" and change Clive's grade, or else Larry faces a legal battle to prove them guilty.
- In Brat Farrar, the protagonist impersonates an heir who went missing years earlier. He comes to realise that the person he's impersonating was murdered. When he impulsively accuses the murderer in a private conversation, the murderer freely admits it, pointing out that Brat can't prove anything and can't even share his suspicions with anyone without first admitting his own wrongdoing.
- In Håkan Nesser's Chief Inspector van Veeteren series of police procedurals set in Holland, The G File deals with van Veeteren's investigation into a murderous sociopath he has known since they were at school together. He knows "G" is capable of murder and knows he most probably murdered his first wife for the insurance money. When his second wife apparently dies of misadventure and over a million guilders of insurance cash is about to pay out, he runs into the same problem. How do you prove, to the satisfaction of a court of law, what you know to be true? Especially since the suspect has pretty much confirmed to you, with a smirk on his face, with no witnesses present, that he did it and it's up to the copper to find the proof?
- Harry Potter and the Chamber of Secrets: At the end, when Lucius Malfoy comes storming into Dumbledore's office, Harry makes the connection of Malfoy trying to get rid of a number of dark items, like the diary that caused all the trouble, before term started and realizes that he is the one responsible for the years events, explaining that Malfoy slipped the diary into Ginny Weasley's stack of textbooks. Malfoy can only say, "Prove it." Dumbledore admits there's little chance of that, but warns Malfoy the Ministry of Magic, Arthur Weasley in particular, will be paying much closer attention to him.
- In Kushiel's Legacy, Melisande stands trial for treason against Terre d'Ange and issues one of these, knowing that all her conspirators died in the invasion she masterminded. Then Phèdre, whom Melisande had Made a Slave in the invading nation to keep her from interfering, steps out from behind the throne, defies her, and delivers the testimony that convicts her. Years later, stories are still told of the exchange.
- When Colin Fischer accuses Sandy Ryan of owning the gun that went off in the cafeteria, the response he gets is "You can't prove anything!"
- Trueman Bradley: At the climax of the first book, Buckley worries that he and Trueman will get in trouble for breaking and entering. Chief Stokowski says, "You bet you will! I'd like to see you find evidence! Go ahead! Show me where the evidence is!"
- Monk. Because the series usually employs the Reverse Whodunnit, Monk will often confront the suspect early in the episode and be challenged not only to prove his opposition's guilt but to explain how they did it in the first place. In a late episode, Stage Magician The Great Torini exaggerates the trope by signing a murder confession before igniting it and leaving Monk with the scraps.
- In Murdoch Mysteries:
- In "Me, Myself, and Murdoch", Murdoch confronts a farmhand employed by a murder victim, asserting that he's actually the dead man's stepson and killed him. The farmhand insists he was born on the other side of the country, points out that he isn't required to carry his birth certificate, observes he is merely not helping the detective and finally says to Murdoch, "Prove it." Murdoch has Constable Crabtree bring in his half-sister Charlotte, who recognizes him immediately and calls him by the nickname ("Boo-boo") she called him in her childhood.
- Late in "The Knockdown", Murdoch confronts the dead boxer's manager with evidence (including the shirt buttons found in the manager's hotel room fireplace) and asserts the manager killed the boxer. The manager dismisses the whole story, saying he burned the shirt because it stank and not because it had incriminating bloodstains on it. At length, he tells Murdoch, "Prove it." Murdoch knows the manager is in love with the boxer's wife (now widow) who has been arrested for the crime, and he also knows she will likely face hanging in part because she is black, so he presses the manager to confess largely to save her life. He also offers an out (suggesting that the manager might have acted in self-defense) to obtain a confession from him and thus exonerate the widow.
- In "What Lies Buried", human remains are found under Station Four's basement floor, together with the shattered pieces of a glass photo negative. After the negative is mostly reassembled, a crucial piece goes missing, and the investigation shows Chief Constable Giles is one of two men in the compromising image. Murdoch interrogates Giles, asking if Giles took the missing piece, and Giles replies, "I've just confessed that I'm a homosexual. My career is over. I'll be dismissed at the next council session. That much I don't contest. But I'm damned if I will confess to a crime when you have not a shred of evidence to back it. If you think I've interfered with this case, prove it."
Murdoch pursues his questioning, and Giles proposes an exchange in "Truth for truth" — his confession for Murdoch's own admission that he released murderess Constance Gardiner from jail several years ago. Then it turns out that Giles' confession was false, and that he was covering for the loyal Constable Hodge, who struggled with another constable who was blackmailing Giles and accidentally killed the man.
- NYPD Blue: A new detective who only got to where he is by Nepotism (he's the nephew of the Chief of Personnel) keeps getting bounced from squad to squad beause he doesn't fit in. Eventually Sipowicz discovers that he may have murdered his wife, setting a Car Bomb in his own car to make it look like an assassination attempt on himself. They're sure that it happened but they don't have definitive proof, so Sipowicz confronts him in an interrogation room, saying that they do have proof but they'll give him the courtesy of allowing him to put in his papers (resign from the job). The new detective, realizing that if Sipowicz really had anything on him wouldn't be giving him this out, doesn't deny the accusation but simply says "prove it." However, he really should have denied it because unknown to him, his uncle the Chief of Personnel is observing from the other side of a two way mirror. The uncle sees how the nephew reacts and realizes that he is guilty, so forces him to resign.
- In Sherlock Holmes, after Holmes triumphantly declares to Larrabee that he can now have him arrested for robbery once he makes his escape, Larrabee scoffs: "My arrest! Ha, ha! Robbery eh— Why even if you got away from here, you haven't got a witness! Not a witness to your name." Holmes answers: "I'm not so sure of that, Mr. Larrabee! Do you usually fasten that door with a knife?" He points to the cupboard door, from behind which a very faint feminine moan is soon heard. Holmes then moves quickly to remove the knife, open the door and liberate the Bound and Gagged Alice Faulkner.
- Many trials in Danganronpa end this way following the Closing Statement/Climax Inference puzzle, where the culprit usually has to be a fought in a Bullet Time Battle with the final Truth Bullet concluding the case by tying them to the crime. Leon Kuwata most famously does in the first game yelling about everything he just heard being stupid theories, before Naegi corners him with the shrink-wrapped tool kits given to all the male students being clearly used in the case they just went through, meaning his should probably be opened up. His only response is Stunned Silence.
- Many of the villains in Ace Attorney will do this, often in the middle of a courtroom, on the witness stand. Defense Attorney Kristoph Gavin actually pulls off a successful challenge during the final conflict of Apollo Justice, but is undone by one thing he couldn't account for — the jury.