[[quoteright:350:[[WesternAnimation/MyLittlePonyFriendshipIsMagic http://static.tvtropes.org/pmwiki/pub/images/mlpfim_perpsweat_3735.jpg]]]]
[[caption-width-right:350:"I want you to ''confess''!"]]

->''"You can get more with a kind word and a two-by-four than with just a kind word."''
-->-- '''Marcus Cole''', ''Series/BabylonFive''

In the Fifties, a desk lamp in an interrogation room would be turned so that a perp would have the light in his eyes and stern questions would come out of the dark as sweat poured down his face. Sometimes, there might be a nice, cool glass of water just out of the perp's reach to "aid" his concentration. This was Perp Sweating.

There has been some escalation since the Fifties. Now the perp has to withstand any number of mind games from GoodCopBadCop to FalseRoulette.
Specific variants:
* BeAsUnhelpfulAsPossible
* BluffingTheMurderer
* ConfessToALesserCrime
* DontAnswerThat
* EnhancedInterrogationTechniques
* ExasperatedPerp
* FalseRoulette
* GoodCopBadCop
* HighAltitudeInterrogation
* INeverSaidItWasPoison
* InterrogationByVandalism
* JackBauerInterrogationTechnique
* LyingToThePerp
* ThePerryMasonMethod
* RabidCop
* RatsInABox
* TortureForFunAndInformation
* TruthSerum
* TwerpSweating (not actually a subtrope, but related)
* VandalismBackfire
* VirtualRealityInterrogation
* WeHaveWaysOfMakingYouTalk

Two character types on whom Perp Sweating almost never works include TheSociopath and people with AspergersSyndrome: two totally different types of people, both on different levels of communication than you. TheSociopath will be two steps ahead of you and retaliate with a HannibalLecture. A person with Aspergers will be seven or eight steps behind (or ahead, if they are high functioning), and get confused by subtle questions, annoyed by a GoodCopBadCop routine, and clam up if you start lying to them. The savvy ones will BeAsUnhelpfulAsPossible to get back at you. Either way you're going to have to rethink your techniques with them.

One major problem with Perp Sweating is that it is often done in an effort to elicit a confession in the absence of evidence actually proving the person's guilt. In other words, the interrogator is assuming the questioned individual's guilt even without a concrete reason. At best, this can be called poor investigative technique and at worst, it can be called a violation of the principle that everyone is presumed innocent until proven guilty.

See also ''Franchise/PerryMason'', ''Series/{{Columbo}}''. But beware any attempt to try this on the PsychoForHire, lest you be reduced to tears by a HannibalLecture. Also, [[RealityIsUnrealistic just 'cuz it happens on teevee doesn't mean it's legal]] - depictions in media often skip the suspect's MirandaRights or [[YouDoNotHaveToSayAnything similar]] [[ReadingYourRights warnings]] (though this can be excused if the setting is in jurisdictions that lack these rights).



* Parodied in the popular "Got Milk?" commercials. In one commercial, a cop interrogates a suspect while placing a package of snack cakes on the table. When the suspect notices the snack cakes, the cop says, "Go ahead, have 'em." The suspect wolfs down the cakes while the cop pours a glass of milk. "Now then," he says as he places the glass in front of the suspect, "We can do this the easy way, or we can do this..." He suddenly slides the glass out of the suspect's reach. "The hard way." The suspect, not having any milk to wash down the snack cakes, gulps loudly.

[[folder:Anime and Manga]]
* ''NininGaShinobuden'' of all series, has one of these when Onsokumaru questions Miyabi about the boy she has a crush on.
* An early episode of ''DominionTankPolice'' has the force doing it as a ''game show'', with the perp strapped to a spinning knife-throwing target, with a hand grenade stuck in his mouth. Oh, and Leona emceeing in a PlayboyBunny outfit.

* ''Film/LAConfidential'' had such a successful Perp Sweating that the men being held were not only in tears, but actually [[BringMyBrownPants crapping themselves]].
* In the 1990 film ''Film/DickTracy'', Dustin Hoffman's character Mumbles is subjected to a deliberately over-the-top example of this.
* ''Film/CastADeadlySpell''. When Lovecraft refuses to cooperate with the police, his friend Lieutenant Bradbury turns a bright light in his face and starts questioning him.
* Harvey Dent does this to the man who [[spoiler:apparently killed Jim Gordon]] in ''Film/TheDarkKnight''. Harvey abducts him from the ambulance, ties him up in a chair, and threatens to shoot him if a coin flip turns up 'tails' unless he talks. The coin is a two-headed one, so Harvey never really intended to shoot the man. Batman puts a stop to this because a) the perp is a mental patient and thus isn't truly culpable for his deeds and b) Gotham's "White Knight" shouldn't be resorting to such unethical tactics.

* Literature/TheActionHerosHandbook - "How to Interrogate a Suspect" discusses common perp sweating techniques and how to tell if a suspect has something to hide.

[[folder:Live-Action TV]]
* Subverted/Inverted/Monkeywrenched in ''Series/LawAndOrderSpecialVictimsUnit'', when they had the killer, but they need to find his latest kidnap victim before she runs out of air. He's GenreSavvy, doesn't drink anything (can't get DNA), doesn't need to poop (can't "trade" him a bathroom break for info), doesn't give them any information, can't be intimidated by even Elliot's best efforts, and they can only hold him for so long. He's a copycat killer, so when TheProfiler Dr. Huang looks at his crimes, he realized that the victims--who, like the original killer, were all mothers--were never raped. They bring in his mother, who reveals that he's a disappointment to her, and he's afraid of the dark. There happens to be a closet down the hall. Awesome ensues. Because apparently ''Law and Order'' takes place in a bizarre parallel universe where TortureAlwaysWorks. And apparently is legal.
** Subverted in another episode where the suspect is a U.S. Marine. Olivia wants to put him in the interrogation room and sweat him but Finn rejects that plan as marines are explicitly trained to resist interrogation and from people with far less restraint than the NYPD. Later when Olivia does try PerpSweating, all of her tactics fail to crack the suspect. Olivia even calls him a textbook sociopath when pictures of the victim's body fail to faze him. Finn has to point out that four combat tours in Iraq would leave anyone jaded.
* In ''Series/LawAndOrderCriminalIntent'', Goren is very good at this.
* 'Series/{{NCIS}}'':
** Leroy Jethro Gibbs is famous for his skill at this. (So, of course, is Tony.) And when Gibbs can't crack them, sometimes he lets Ziva have a turn. Failing all else... off to see the CreepyMortician.
** Gibbs also has a unique advantage: he often outranks any military man he's perp-sweating, forcing them to be more truthful.
* Subverted in an episode of ''Series/{{Seinfeld}}'' where Newman interrogates Jerry, but sits himself under the hot lamp instead of Jerry. Newman gushes sweat while Jerry sits comfortably and sips a refreshing soda.
* In ''Series/VeronicaMars'', Keith Mars seems to enjoy doing this.
* In ''Series/StargateSG1'', Teal'c can make anyone talk by just staring at them.
* So can Garak in ''Series/StarTrekDeepSpaceNine''. He once describes how he interrogated a guy by staring at him... ''for three hours''. In the same episode, Garak presents a more straightforward example: using a device that prevents Odo from reverting to his liquid form as his biology requires; making him progressively more uncomfortable the longer he holds back the information Garak wants. It eventually crosses the line into outright torture.
* Seen in the pilot episode of ''Detroit 1-8-7''. After a suspect feels smug at having frustrated the rookie detective, the rookie's senior partner goes into the room, sits down, and just stares.
* Happens to a female IMF agent in an episode of ''Series/MissionImpossible'', where the team are trying to stop the BananaRepublic of Terra Nueva invading democratic San Cristobal. The fact that she's wearing a towel also clearly implies she's been strip-searched. They find the information they are supposed to find [[spoiler: microdots in her contact lenses]].
* ''Series/PowerRangersSPD'' once did this in the Rangers' own typical BunnyEarsLawyer way, subjecting the poor perp to the Pink Ranger's hit single ''Me'' and the [[CloudCuckooLander Green Ranger's]] stream-of-conscious rambling until he talked.
* Humorously inverted in ''Series/{{Firefly}}''. in one scene Jayne makes the interrogator start to loose his cool by staring at him from a slouching posture with a slight smirk and completely ignoring any questions. This is made even more hilarious by the scene interspersed with shots of the Alliance search party finding Jayne's impressive (one might even say ludicrous) arsenal.
* On ''Series/LasVegas'', a snarky casino guest who's being questioned by Ed about a robbery pulls a lamp around to shine in his ''own'' eyes, then quips that he's ready for the interrogation now.
* ''Series/{{Batman}}''. In the episode "The Dead Ringers", Commissioner Gordon and Chief O'Hara put Harry (Chandel's EvilTwin brother) under a bright light while questioning him.
* ''Series/BuffyTheVampireSlayer''. Mild and geeky Willow enjoys interrogating Jonathan (with desk lamp) when the Scoobies suspect him of murder in "Go Fish". The gag is repeated again in "Earshot".
* ''Series/CriminalMinds'' used a lot of interrogation in its early seasons, as, oftentimes, the team would have a completed profile of the [=UnSub=] but little in the way of actual physical evidence- thus requiring a confession.
* PlayedForLaughs in one episode of ''Series/BlackBooks'', when Bernard, Manny and Fran are getting ready to go on holiday. Bernard and Manny tie Fran to a chair with a [[HardDrinkingPartyGirl glass of wine]] just out of reach, turn a lamp so that the light shines right in her face... and confront her with the fact that she has packed her suitcase full of [[AllWomenLoveShoes shoes]] and nothing else.
-->'''Manny:''' We're here to help you.
-->'''Fran:''' You don't understand!
-->'''Bernard:''' ''(opens the suitcase dramatically, revealing the shoes)'' We understand that you're ill.

[[folder:Newspaper Comics]]
* ''ComicStrip/CalvinAndHobbes'' does this a lot:
** One incident had Calvin's mother going for a parent-teacher interview with Miss Wormwood, which prompts Calvin to start packing a suitcase to run away. (Calvin does have a perpetually guilty conscience since he misbehaves ''all the time.'') When his mother comes back and tries to talk to him about the conference, she inadvertently Perp Sweats him and he begins panicking as he tries to explain what he thinks Miss Wormwood told her:
-->'''Calvin''': Lies! Everything Miss Wormwood said about me was a lie! She just doesn't like me! She hates little boys! It's not my fault! I'm not to blame! She told you about the [[NoodleIncident noodles]], right? It wasn't me! Nobody saw me! I was framed! I wouldn't do anything like that! I'm innocent, I tell you!
** Another time Calvin broke his dad's expensive binoculars, and burst into a hysterical confession at the dinner table when his dad hadn't even found out yet.
** And then there was the incident with sending the family car into a ditch ...
* Used in a couple of story arcs in ''ComicStrip/FoxTrot''.
** After punching another kid in the face at school ([[BerserkButton he was making fun of Peter's girlfriend]]), Peter comes home expecting his parents to have been contacted and to be chewed out for it. When his mother mentions that the school called her, he bursts into an annoyed monologue about how he screwed up and he knows it, thank you very much... only to have her reveal that they simply called to say someone found his wallet and immediately jump on him for whatever the "fight" was that he mentioned.
** In a similar instance, Peter's mother comes into his room and asks him to "guess what he found under his mattress." He flips out and quickly insists that [[IReadItForTheArticles he only reads those magazines for the articles]]. Cue her explaining that she found his baseball mitt (he put it under his mattress to break it in) and demanding to know what magazines while Peter [[PerpSweat begins sweating profusely]].

[[folder:Video Games]]
* In ''VideoGame/GhostTrick'', the backstory of the primary antagonist results from one of these going very badly wrong. An innocent man at the time, he'd been brought in as the main suspect for a crime, and the rookie detective went too far in implying what would happen to him if he didn't co-operate. Scared out of his mind and beyond rational thought, he took the detective's gun and fled the police station, forcing the cops to pursue him to a certain park...

* Parodied in ''Webcomic/EightBitTheater'' with this exchange:
--> '''Red Mage''': Did you take Matoya's crystal?
--> '''Bikke''': No!
--> '''Red Mage''': No? Or... ''yes?''
--> '''Bikke''': Er... But I... And you... Uh... ''Damn'' ye and ye black ops mind games. Yes I stole it! And I'd steal it again given half the chance!

[[folder:Western Animation]]
* On ''WesternAnimation/JimmyTwoShoes'', Jimmy attempts to do this to Beezy. Being [[ThePollyanna Jimmy]], he doesn't do it very well. Being [[TheDitz Beezy]], it's effective anyway.
* Referenced in ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' of all series, where Pinkie Pie uses this to "interrogate" Spike in "Party of One".
* Sid plays at this with Woody in ''WesternAnimation/ToyStory'' before launching into WeHaveWaysOfMakingYouTalk.
* Kent Mansley in ''WesternAnimation/TheIronGiant'' does this to Hogarth.
* Done to Chuck the Evil Sandwich Making Guy in one episode of ''WesternAnimation/WordGirl''.
* ''WesternAnimation/MrBogus'' does this to Mole in the third act of the episode "[[Recap/MrBogusS2E7BogusPrivateEye Bogus Private Eye]]", when interrogating him about the theft of Mr. Anybody's watch.
* In the second episode of ''WesternAnimation/StarVsTheForcesOfEvil'', the goons from St. Olga's Reform School for Wayward Princesses do this to Marco to make him detail where Pony Head is. When this fails at first, they proceed to flicker the spotlight, which prompts him to say:
-->'''Marco''': STO-HA-HA-HOOOP! That is really annoying!