The Evidence Dungeon is the lair of the villain, which is full of all the things a good villain needs to do their work...and to be charged with said work when the police find it.
The defining feature of an Evidence Dungeon is the expositional shit lying around that any sane person would hide or dispose of immediately. It's a place that is not only the villain's lair but is also where all the incriminating evidence is kept. This may make for a very foolish criminal, or just the right kind of delusional mind that would commit the crimes in the first place.
The Evidence Dungeon combines Chronic Evidence Retention Syndrome, the villain's lair and a healthy dollop of stupidity. It can overlap with conspiracy theories, the proof of their insanity and gruesome bad guy trophies. If the evidence is part of a creepy collection, you might be in The Doll Episode.
It is the inverse of an Orgy of Evidence which is done intentionally to mislead. An Evidence Dungeon is unintentionally discovered, a convenient dumping ground of evidence and plot clues for The Protagonist.
Differs from Chronic Evidence Retention Syndrome which can be more specific, for example, keeping a single incriminating note or weapon. Also not the same as a Room Full of Crazy which proves insanity but not necessarily guilt. For a Serial Killer, the place can be his Torture Cellar. The Big Board can be a non-insane version of Evidence Dungeon.
A Smug Snake or The Starscream might collect an Evidence Dungeon, too arrogant to believe that they would be caught. A Big Bad or Big Bad Wannabe has far-ranging plans with the correspondingly abundant evidence. Often it is the Serial Killer either collecting trophies of their work or too insane to realize all the clues just laying around.
A detective/doctor/family member can stumble across Evidence Dungeons, shortly followed by some time Alone with the Psycho. Often this leads to an attempt on the discoverer's life by the owner of the room. These rooms can be also be susceptible to cases of vanishing evidence as well.
- The narrators in Hideshi Hino's horror stories (like Panorama of Hell) invariably have houses or shops full of crazy, filled with disturbing paintings, horrible things in jars, and/or macabre junk.
- In 52, time-traveling superhero Booster Gold breaks into the secret base of veteran chrononaut Rip Hunter looking for advice on temporal anomalies. He finds Rip missing, his time machine broken, and a chalkboard in his bunker covered in crazy theories, dozens of photos and magazine covers of Booster himself. It later turns out that Rip was absolutely sane and absolutely right, but the photos weren't of Booster — they were of his (possessed) Robot Buddy Skeets.
- Johnny the Homicidal Maniac's entire house is stuffed with evidence. Stuffed animals are nailed to the walls, rooms are covered with philosophical meanderings, posters are stuck all over the place, as well as macabre little messages (Enjoy your stay-the management). Not to mention the wall he paints with the blood of his victims in an attempt to placate cosmic/demonic monstrosities. But hey, he's crazy.
- In both comic and movie versions of Watchmen, Veidt didn't erase the computer files that detailed his plan to unbalance Dr. Manhattan into leaving Earth, and information on his ultimate plan, even though the Manhattan plan had been successful (so far as he knew) and he'd already kicked off the second, so there was no need to keep the files at all. Most likely Veidt knew his friends would pursue and confront him and wanted to control that variable in his plan. Why else would the "smartest man in the world" keep them in a computer with not only an obvious password but a prompt that basically says "Password incorrect: you need to ADD ANOTHER WORD"?
- The Farm at North Cross and Lennox from the Sin City series featured in "The Hard Goodbye," where it was Kevin and Cardinal Roark's base of operation for their cannibalistic impulses has (at minimum) the decapitated heads of their victims.
- The Far Side has a rat in prison talking to his cellmate: "I would have gotten away scot-free if I'd gotten rid of the evidence... but shoot, I'm a pack rat."
- Doug's train car/lab in Zootopia is packed with incriminating evidence including a map with the photos of all the fourteen missing mammals.
- I Know Who Killed Me: Lindsay Lohan's Dakota stumbles into the killer's lair, chock full of murder weapons, buckets of blood and a freshly exanguinated victim.
- The Texas Chainsaw Massacre: The house is an abattoir with damning evidence in every room. Justified as the murderous family's house is so far removed from civilization that it is only discovered by accident.
- In Saw, Jigsaw's lair is where he crafts his traps, the scene of several crimes and an absolute mountain of evidence. Justified as Jigsaw has terminal cancer and being discovered is all part of the plan.
- John Doe's apartment in Se7en is connected with all his crimes. It has photos of Gluttony, the severed hand of Sloth, 2000 handwritten diaries detailing his thoughts and a gob-smacking amount of materials connected to his crimes. But no fingerprints, meaning it was all part of John Doe's work.
- The photos that Robin Williams's Sy Parrish keeps in One Hour Photo fuel his voyeurism and is a mountain of evidence against him. Doubles as a Room Full of Crazy.
- In Unbreakable, Samuel Jackson's Elijah 'Mr. Glass' Price both engineered the disasters and keeps all the evidence of them in the back room of his comic gallery. Once David Dunn touches him, he looks on the obvious evidence with new eyes.
- Gothika there was an actual dungeon where a pair of guys kept VHS tapes (evidence, if you will) of their conquests... but no wall of crazy, with stings and maps and such.
- In Kiss the Girls, at Will Rudolph's place they find a freezer with newspaper clippings of the victims and dismembered feet.
- Minority Report subverts this. When John Anderton searches Leo Crow's apartment, he finds the bed is covered in photos implying that Crow kidnapped and molested dozens of children (including Anderton's own son). It turns out that the photos had been faked and what appeared to be an Evidence Dungeon was actually an Orgy of Evidence. Lampshaded by Witwer, who (having pursued Anderton up to that point) immediately becomes suspicious, correctly concluding that the massive, implausible flood of evidence more likely points to a frame-up.
- In [REC], the closest anyone gets to an explanation is a Room Full of Crazy covered in newspaper clips about a "Ninha Medeiros" who seems to have been infected or possessed, a recorder that plays back some ramblings about a virus, an infected hyper-aggressive little boy and, finally, the Ninha herself that kills the last two survivors.
- Memento features a much more personal version of this in the form of Leonard's tattoos. ' Almost all the evidence needed to indict him for multiple murders is tattooed on his body.
- Even worse, but seemingly more innocent: "Remember Sammy Jenkis." This is Leonard's way of using his own condition against himself, to continue perpetuating the lie that Sammy Jenkis as an existing person and that he's not a walking, talking Evidence Dungeon. By putting it on his hand, he ensures he'll look at it every so often.
- The attic in The Skeleton Key is just chuckful of Voodoo evidence.
- The basement of the pawn shop in Pulp Fiction, where Vince and Marsellus are held Bound and Gagged and latter is being sodomized.
- House of 1000 Corpses takes this and all the tropes of the Texas Chainsaw tradition and cranks them to eleven. (The sheer number of skeletons eventually revealed, each and every one of them implying an unsolved missing-persons report strains Suspension of Disbelief.)
- Hostel There is so much evidence in place that everyone involved would be jailed for eternity. However, it is implied that Depression-style economic conditions make the area more or less lawless.
- The Water Street Butcher from The Poughkeepsie Tapes saved ridiculous amounts of evidence in his lair.
- Played with in Hot Fuzz, when Nick Angel uncovers the evil conspiracy at the courtyard of the village's local castle. While being pursued he finds a basement stacked full with all of the killer's previous victims. However, when he proposes going to the police on this evidence, Danny says that the culprit will just "make it disappear".
- Dead Calm: Hughie rows away from a slowly sinking boat to a couple, John and Rae Ingram, on a vacation cruise in the middle of the Pacific. Hughie claims his companions all died of food poisoning and the boat was damaged in a storm. John, a Royal Australian Navy officer, is suspicious of Hughie's story and rows out to the stricken boat and finds five bodies belowdecks and a video suggesting Hughie violently murdered everyone in a fit of rage. Unusual for this trope, Hughie damaged the boat to dispose of the evidence, then overpowers Rae and sails away, leaving John to die and almost gets away with it.
- In Captain America: Civil War, the Evidence Dungeon is intentionally revealed. In the last part of the movie, Zemo makes a call to the hotel he was staying at so that the corpse of the psychiatrist he killed is discovered, as well as plenty of evidence that the Winter Soldier bombing the U.N. building was staged. This is to convince Tony Stark of Bucky's innocence at the exact right time for Iron Man to join him and Captain America at the Siberian HYDRA facility.
- The Silence of the Lambs: Once Clarice finds Gumb's lair she discovers ALL the evidence. Gumb's house has pictures of butterflies all over the place, swastika quilts, and dead people. He also has a collection of newspaper clippings of his exploits, plastered on the inside of the door of a large cabinet. Directly in front of it is his in-progress woman suit.
- In The Girl with the Dragon Tattoo, first book of The Millennium Trilogy, Martin Vanger maintains an extensive Evidence Dungeon with knockout gas, innumerable knives, scalpels and torture instruments, and pictures, video and audio tape recordings of dozens of victims. Justified as Vanger is a billionaire industrialist living in an incredibly remote corner of Sweden and his Evidence Dungeon was behind an electronically locked steel door in his basement. He had every reason to believe he wouldn't be discovered.
- Patrick Bateman in American Psycho uses both his apartment and appropriates Paul Owen/Allen's apartment after killing him to commit most of his murders. In his apartment, there is a head in the fridge and numerous implements of murder and torture. In Paul Owen/Allen's apartment, there are two bodies hanging on hooks in a closet, another on the bathroom floor and a room with 'Die Yuppie Scum' scrawled on the walls. Subverted as the ending implies that Bateman may be having psychotic delusions about his murders. As he is an incredibly unreliable narrator, it calls into question everything we've seen and whether the 'evidence' was really there.
- In Unique, Sajan and Jan unwittingly team up to find the serial killer's dungeon. It's supposed to be a furniture workshop, so all the power tools and even the welding equipment belong, but the dentist's chair, bondage equipment, surgical instruments and reek of disinfectant definitely don't (not to mention the psychic aura of cruelty and agony that makes Sajan physically sick).
- The Dresden Files: In White Night, Harry Dresden is investigating his half-brother, Thomas. During the investigation, Harry snoops around the suspect's apartment, and stumbles onto one of these. In an inverse, the room isn't meant for women Thomas is hunting, but rather women the real killer is hunting and Thomas is rescuing them. Soon after, to avoid the police from finding the same room, Harry must pretend to be Thomas' gay lover to explain his appearance at the place.
- Minnesota Shrike's nest aka The Antler Room in Hannibal counts as a slight one as he left enough evidence for FBI profiler Will Graham.
- Bones: In the episode where Booth & Brennan are on their honeymoon they stumble into a murder investigation, where it turns out the Victim of the Week is a Former Nazi. They learn this by finding a secret room in his estate filled with all his old Nazi paraphernalia.
- Played with in the second episode of Quantico, where the trainees are allowed to visit recreations of three rooms where three different terrorist attacks were planned, and they are asked to comb through the rooms and determine which one, if any, contained actionable evidence of an impending threat. It turned out that none of them did.
- Season 2 of Terminator: The Sarah Connor Chronicles had a basement with names, numbers and dates written on the walls, in blood.
- Averted in The Wire; most criminals are always shown dumping their guns or otherwise eliminating eviedence. Even the otherwise dumb-as-bricks ones are smart enough to listen to their cleverer colleagues and dump their guns.
- In the Masters of Horror episode "Incident On and Off a Mountain Road", the albino serial killer Moonface performs all his kills in his dungeon underneath his cabin. He typically carves his victims' eyes out with an electrical drill.
- In Buffy the Vampire Slayer Spike seems especially prone to these. In season 5 he leaves an underground shrine of photos and stolen possessions that shows he's dangerously obsessed with Buffy. In season 7, he turns the basement of a house into a burial ground for all the people The First has made him kill.
- The nature of Chaos-inspired madness in Warhammer and Warhammer 40,000 means loads of evidence just left around for the Inquisition.
- In Betrayal At House On The Hill, explorers of the eponymous house have a chance of coming across a medieval torture chamber complete with iron maiden and floor drain in the basement.
- In Clue, the very premise is finding all the evidence that the murderer left just laying around.
- Sweeney Todd: The Demon Barber of Fleet Street has a variation of this with the meat room of Mrs. Lovett's pie shop. Sweeney Todd starts murdering his customers and baking them into pies. The smell of the human flesh burning is pumped into the air and just by the nature of butchery, loads of visera must be left around.
- In Danganronpa: Trigger Happy Havoc, one character finds an entire hidden room stacked with revelation-packed documents, left there for no apparent reason. The room held enough importance that The Mastermind was willing to come out of their hiding place to attack The Hero.
- Call of Cthulhu: Dark Corners of the Earth, in the first mission, you eventually reach the basement of a cult's house, only to find a man completely gutted, strung up in a machine with his arms at his sides and his various organs beating away in dozens of other containers across the room. To top it off, corpses in various states of decay and with various missing organs are scattered around, indicating this victim isn't the first.
- In Vampire: The Masquerade Bloodlines one encounters a serial killer who has various rooms in his home filled with torture equipment, limbs, and textbooks, ultimately ending with you in his main dungeon as he beats you with a severed arm.
- In The Elder Scrolls IV: Oblivion, an insane murderer wanting to destroy the Dark Brotherhood to avenge the death of his mother has a lair in the cellar of a lighthouse. Among other things, the place holds: a rabid living dog, multiple rotting dead bodies (possibly as dog food), walls splattered with blood, the decayed head of said mother, and a really creepy diary. Half of it a personal message to his mother, promising revenge, the rest is the word "killhim" written over and over, in blood.
- The Polar Academy in Knights of the Old Republic II contains one. Atris converted an old irrigation station into a replica of the Jedi Temple and calls herself the "last of the Jedi" to a bunch of Echani "handmaidens" she's gathered. Her private meditation chamber is full of Sith holocrons that whisper to her constantly and speed her along the path to the Dark Side. Any Jedi seeing her chambers would immediately suspect she's either fallen or a Sith.
- Noticeable in Fallout 3 and Fallout: New Vegas. Whenever you get a quest to investigate someone, you usually find three or four pieces of evidence of wrongdoing laying around or in easily accessed safes. Most striking is Andale, from Fallout 3; A small settlement of only two families, who act like the Great War never happened and call Andale "the greatest town in Virginia". But then you go into the shed or the basement, and find out that both families are cannibals...
- In Path of Exile, Piety's base in the Lunaris Temple fits the trope, putting her hideous industrial-scale cruelty on display. You knew she was an enemy even before you found the place, but by the time you've finished wading through the literal lakes of blood there, walking between carts full of corpses and slaughtering an army of tormented abominations that used to be people, you're left with absolutely no doubt that she needs to die.
- The assault on Makarov's safehouse in Modern Warfare 2. Inside, you can find schematics related to his terrorist attacks, enormous caches of weapons to outfit his personal army, valuable computer data your commanding officer needs to find Makarov, easy-to-miss expository newspaper clippings that are the only place in the game explaining Makarov's motivations, and... a blow-up doll.
- This is played with, in Girl Genius, with Castle Heterodyne. The entire castle could be said to be a house with extensive proof of tortuous experimentation labs, monstrous creations, and hideous traps, so for the hero who manages to really amuse the castle, they have a torture chamber filled with... light music, bright colors, and a rather extensive waiting list. As a cast member puts it, "It's more like psychological torture."
- Stuart Wellington of The Flop House podcast was worried (pre-marriage) that his apartment could be taken as an Evidence Dungeon, if you looked at it with the wrong set of eyes.
- South Park: In the episode "Cartman's Incredible Gift", South Park is terrorized by a serial killer who severs the left hand from his victims. The cops manage to find his hideout, but at first don't think they're in the right place because they believe all the collected trophies are right hands.
- Often occurs with Scooby-Doo villains, who leave evidence all over the place for meddling kids to find.
- The Nazis; after the war, the Allies were astonished at the amount of evidence and paperwork related to the Holocaust they were able to uncover. The sheer amount of incriminating evidence pretty much made the convictions at the Nuremberg Trials a foregone conclusion.
- When John Reginald Halliday Christie rented out a room in his house, the new tenants started to wonder about the smell from a papered-over wall closet. When the police finally came to search 10 Rillington Place, the back garden fence was found to be propped up with a human thighbone.
- In his apartment, Jeffery Dahmer had muriatic acid used to flense corpses, photos of dismemebered corpses in various stages of decomposition, four severed heads in the refrigerator, seven cleaned skulls, a full torso in the freezer, three torsos in a 57 gallon plastic drum and two full skeletons. The chief medical examiner later stated: "It was more like dismantling someone's museum than an actual crime scene." All it took was police officers just walking into his apartment to provoke an arrest.
- Dr. Henry Holmes built a three-story hotel in Chicago to serve as his Torture Cellar. After his arrest, police found four skeletons in a lime pit, a pile of human bones mixed with animal bones, a dissection table covered with dry blood, and a pile of bloody women's clothes and jewelry belonging to victims,
- Ed Gein's home combined this trope with Entire Farmouse Full Of Crazy. He decorated his home with body parts from graves he dug up, and eventually two victims. This included (but was far from limited to): A wastebasket made of human skin, human skin covering several chair seats, skulls on his bedposts, a corset made from a female torso skinned from shoulders to waist and a mask he'd made from victim Mary Hogan's face in a paper bag. The police arrested him immediately on investigating.