History Main / LivingLieDetector

[[folder:Web Original]]

* ''WesternAnimation/AvatarTheLastAirbender'': Toph Beifong has a DisabilitySuperpower resulting from her ability to "see" with vibrations (since she's blind), including heart rate, breathing patterns, and other vital signs that react when someone lies. There's only one time that it ever failed...[[note]]It is probable that Azula is a sociopath who has no emotional reaction to lying and thus it cannot be detected, just as real world lie detectors. It is odd that Toph never deals with the opposite problem, a nervous person appearing to lie when they aren't[[/note]]
-->'''Toph:''' And stick to the truth. I'll be able to tell if you're lying.\\
'''[[ConsummateLiar Azula]]:''' Are you sure? I'm a pretty good liar. I am a 400-foot-tall purple platypus bear with pink horns and silver wings.\\

** It is this, plus her lack of emotional connection with Zuko, which allowed her to be rational about his presence in the Western Air Temple. She could tell he was being sincere when he offered to help Aang and complained that the others were the blind ones for allowing their emotions to cloud their judgement. A point that they then only reinforce by attempting to deny it.
** This can also help in finding out when someone's been {{brainwashed}}, like Toph did with Jet in the episode "Lake Laogai": He claimed he had been living peacefully in Ba Sing Se ever since he arrived, but Smellerbee claimed Jet had been captured by the [[SecretPolice Dai Li]] a couple weeks ago. Toph sensed they were both telling the truth, in a way, with Jet ''thinking'' he was telling the truth, and Smellerbee telling the ''actual'' truth.

** In ''[[Manga/JoJosBizarrePhantomBlood PhantomBlood]]'', Robert E. O. Speedwagon, a reformed mugger operating in Ogre Street, has lived in those conditions for so long, he could tell whether someone was good and evil just from their smell. It allowed him to see past [[MagnificentBastard Dio's]] outward-facing personality and see him for the man he truly is.

* Three examples in ''Manga/JoJosBizarreAdventure''.

* Fear in the ''VideoGame/MetalGearSolid3'' fanfic ''Fanfic/TheJoyOfBattle'' is a human lie detector. He explains it simply to Sorrow after finishing his sentences for most of a scene: "I'm perceptive."

* In the Jennifer Lynn Barnes novels ''Golden'' and ''Platinum'', Lexie James can see truth as if it were a physical property, allowing her to instantly determine the truthfulness or falsehood of any statement. This isn't limited to detecting lies, as it can also be used to determine the truthfulness of guesses and conjectures and also allows her to persuade other people to believe an otherwise dubious statement.

* According to Malcolm Gladwell's book ''Blink'', a particular scientist was not just a Living Lie Detector but could discern things about a society just by looking at the facial expressions of various members for a few seconds. The book claims (and while Gladwell's science is often erroneous in the book, the individual anecdotes themselves are usually true) that he was able to do so by understanding micro-tics, twitches of facial muscles that everyone sees but doesn't interpret because they go too quickly.
** He's probably referring to Dr. Ekman who, in fact, advises the use of a high-speed video camera (microexpressions last less than a second) and says that everything else should be ruled out before deciding that a statement is a lie.
** The same book also had an anecdote about a different psychologist who created a computer program that uses data from a fifteen-minute conversation between a couple to tell whether or not they'll still be together in fifteen years. The accuracy? 80%.
* There are classes that teach you what people do when they lie. So they're being taught how to become a living lie detector. Unfortunately, most people are only slightly better than chance at determining truth from falsehoods. Since most judgments never go challenged, people also tend to think of themselves as much better at detecting lies than they actually are. Police, citizens, and a coin all scored close enough to each other to not be considered statistically significant despite the officers having had training.
* The problem with this trope in RealLife is that although you can tell what emotion a person is feeling by looking at the body language, you can't tell why they are feeling it. A person who is showing signs of fear may be afraid you'll see through the lie, afraid you'll think they are lying when they aren't, or afraid they left the stove on.
** Also, this often does not help you distinguish what is fact from what is ''believed'' to be fact. When your body language tells "truth", it merely confirms the person's ''belief'' in that statement, not its factual veracity. A die-hard Flat-Earth theorist could swear to the Earth being flat with his last breath and no lie detector, living or otherwise, would ever so much as twitch.
** Then there's the matter of people whose body language and/or emotional responses don't fit the social norm, e.g. Neurodivergent people, people with a variety of personality and/or mental disorders, trauma responses, etc.
** For that matter, classes on how to fake these things are available in most schools. They call it "acting".
* Humanity as a whole. It is thought that what allowed humans to form larger social groups and establish trade for mutual advantage ages ago when other primates just as intelligent were inherently distrustful, is that humans were good at telling who to trust and who not to trust allowing them to trust strangers from other human groups.
** This is not entirely accurate though as society still has many people who are narcissists, psychopaths, or are consummate liars that can end up in positions of power and privilege. It is even found that those who lack empathy are able to get more [[https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.psypost.org/2016/06/speed-dating-study-finds-narcissists-psychopaths-get-dates-dark-triad-43452&ved=2ahUKEwiZyZKKqq2BAxXQmmoFHVLZDQ4QFnoECA4QAQ&usg=AOvVaw12dYxDKKuZqCr6uoUXXlWU dates]] than normal people and [[https://srcd.onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-8624.2012.01839.x overcome]] being frozen in fear easier than empathetic people, so the theory might be incorrect in that humans formed due to our intelligence and ability to spot obvious lies, but not be able to spot those of people good at lying to the point of it being a mental condition and habit.
* Inversion and subversion: in 1993, then president Bill Clinton called up KMOX radio in St. Louis and said on the air "after I get off the phone with you today, Rush Limbaugh will come on and will have three hours to say whatever he wants and I won't be able to defend myself. There's no truth detector." Limbaugh countered: "We need no truth detector. I ''am'' the truth detector." Subverted in that at least two books have been published consisting almost entirely of listing things Rush Limbaugh has said and then contrasting those statements with the contrary actual facts.
* Here's a tip: if you want to tell if someone is lying, look at their eyes. If they glance away just before, during, or directly after a statement there's a chance they're lying. Liars have trouble looking their interrogators in the face and will try and divert their gaze when they can. This is harder with women (who tend to be more socially adept than men) and easier with children ([[ChildrenAreInnocent who are obviously more naïve and inexperienced than adults]]). But it can backfire too -- many people are aware of this test, and will therefore make absolutely sure to look their questioner right in the face. Of course, if they suddenly stare directly after a conversation of only occasional glances, that's a giveaway as well. As with a polygraph test, the thing you're really looking for is a sudden change. And autistic people tend to have trouble with eye contact in general, so it won't work on them. Plus eye contact is considered rude or aggressive in many cultures, so they might just be uncomfortable.

* ''WesternAnimation/AvatarTheLastAirbender'': Toph Beifong has a DisabilitySuperpower resulting from her ability to "see" with vibrations (since she's blind), including heart rate, breathing patterns, and other vital signs that react when someone lies. There's only one time that it ever failed...

* ''Literature/TalesOfInthya'': Truthsayers, rare magic users, are capable of telling if anyone lies.

* ''Literature/TheQueenOfIeflaria'': Truthsayers, rare magic users, are capable of telling if anyone lies.

* ''Webcomic/TheGreenhouse'': The demon 'Red' always knows. She can even tell when her [[DemonicPossession host]] is lying to herself in her own thoughts.
-->'''Red:''' Humans give off a different feel... an energy when they do not tell the truth. I would know, you are constantly lying to yourself.
* ''Webcomic/{{Muted}}'': Demons can sense when humans are lying. This is actually how Silvia got her scar; when she was first summoning her familliar, she was trying to deceive it, and sensing her dishonesty, it attacked her.

See also PinocchioNose, YouCanAlwaysTellALiar, TheTell. ExactWords can sometimes help against this, but don't bet on it.[[note]]Depending on the kind of {{phlebotinum}} he uses, the lie detector may pick up on your intent to deceive even if your exact words are literally true.[[/note]]

* ''WesternAnimation/LiloAndStitchTheSeries'': One episode featured a literal living lie detector in Experiment 032, whom Lilo christened "Fibber". Jumba originally designed Fibber under the cynical belief that society is heavily based on people not telling the whole truth, and having people's secrets and little white lies exposed would cause untold chaos. Since the episode in question revolved around Pleakley trying to get out of an ArrangedMarriage by [[TheBeard pretending he was already engaged]], this resulted in Fibber going off every 30 seconds or so for most of the episode (and [[JerkassHasAPoint proving Jumba kinda had a point]]).

* ''Manga/TheSevenDeadlySins'' has Galan of the Ten Commandments. As the "Truth" of the Ten Commandments, he has the power to detect whether someone is lying to him or not. [[TakenForGranite His power also has the added twist of turning the liars into stone.]]

* Creator/ChristopherWalken in ''Film/TrueRomance'':
-->'''Coccotti:''' Now there are seventeen different things a guy can do when he lies to give him away. A guy has seventeen pantomimes. A woman's got twenty, but a guy's got seventeen. And if you know 'em like ya know your own face, they beat lie detectors to hell.

* Timothy in ''Film/TheLongKissGoodnight'' frequently and proudly announces his status as one of these -- which makes it funnier when ''no-one lies to him for the entire film''.

-->'''[[Creator/ArnoldSchwarzenegger Ah-nold]]:''' Based on voice stress computations, I calculate a 79.5% chance you will not pull dat trigger.
* ''Film/Daredevil2003'': Like his comic counterpart, Matt uses his ability to read heartbeats to find out if an accused rapist is telling the truth on the stand. He's not. In the director's cut, Matt is thrown off when both the witness and the suspected murderer seem to be telling the truth. He later finds out that the witness has a pacemaker
* Creator/RobertDeNiro's character in ''Film/MeetTheParents'' has this ability by grasping the wrist of whomever he's questioning.
** Or so he claims. After all, if you can put someone in such a state of fear that they're too scared to lie, and they're convinced that you'll know if they do, then you already know that every word they say is going to be the truth.
** ''Film/LittleFockers'' seems to imply that Jack's ability is real as he grabs Greg's wrist without telling him he's about to do it. Plus Greg doesn't seem to be afraid of or be intimidated by Jack as much as he is in the first film. Jack seems to be satisfied with the results of this and believes that Greg is telling him the truth.
** At the same time, he gets a lot of stuff wrong in the two sequels and is then shocked when it happens.
* ''Film/TheIncredibleHulk2008'': After an attack on the Hulk (once again) goes horribly wrong, involving Betty Ross being injured and the Hulk escaping with her, General Ross visits Doc Samson, Betty's at-the-time boyfriend, who had tipped him off to Banner/Hulk's location (and [[MyGodWhatHaveIDone was currently regretting it]], as Hulk tried to protect Betty when the actions of the army almost killed her). When Ross gives him his word that Betty's safety is his first priority, over capturing the Hulk, Samson stands up and says; "Y'know, I consider it a matter of professional practice that I can always tell when someone is lying to me... and you are."
* ''Film/{{Cypher}}'': Morgan Sullivan's last mission is to a maximum security data bunker. While waiting for a data transfer to take place, the systems administrator conversationally brags/complains how he was the best at spotting moles and detecting lies, before he was obviated by [[LieDetector high-tech biometric monitoring]] and stuck in a dead-end job. He then proceeds to demonstrate with a casual interrogation of Sullivan.
* The titular character in ''Film/MrBrooks''. A neat example in that he never talks about or tells anybody about this ability. It also primarily manifests through his ImaginaryFriend Marshall. He's also secretly the [[SerialKiller Thumbprint Killer]] despite being a successful company owner and philanthropist, which is part of the reason he's so good at this and secretive about it.
* The entire premise behind ''Film/DakotaSkye''. She not only can tell when someone's lying, but she also sees the truth in her mind (at least, as far as the speaker knows it). So when a history teacher blatantly lies about UsefulNotes/ChristopherColumbus and UsefulNotes/ThomasJefferson, she sees in her mind what he's not saying about them. The main reason she's attracted to Jonah is that he ''never'' lies to her, even about things that almost every other guy would lie about, if only to make her feel better.
* Franchise/RoboCop can determine how ''likely'' it is that someone is being truthful (and estimate a percentage to the claims) by listening to the person using his cybernetic-enhanced senses, presumably by measuring stress levels in voice tone the way an actual polygraph test does.
* Ava from ''Film/ExMachina'' can use her enhanced senses to detect when someone is being untruthful via noticeable micro-expressions.

* ''Literature/HarryPotter'':
** Voldemort "almost always knows when someone is lying to him." He's not super-sensitive or precognitive, just casual about [[MindProbe boring into others' minds]]. [[spoiler:Snape's pretty good at this as well, as is Dumbledore.]]
** There's also a corresponding art to ''protecting'' oneself from lie detection. At the beginning of [[Literature/HarryPotterAndTheHalfBloodPrince tome 6]], you know that [[spoiler:Snape was able to fool Dumbledore, Voldemort or both.]] Later in the book, it's revealed that Bellatrix is accomplished in it - likely so that she will keep secrets in the event of capture.
* ''Literature/TheLordOfTheRings'':
** Gandalf explains to Pippin just before meeting Denethor that it is extremely difficult to deceive him, and dangerous to try, due to his Númenórean psychic super-powers (actually just knowledge of psychic techniques that isn't widespread and having a ridiculous age advantage). His son Faramir seems to have inherited this ability, as he is able to immediately detect when Gollum lies to him. It should be noted here though that Pippin has an extraordinary ability to conceal his mind for someone his age.
** Éomer claims that the Rohirrim have some measure of this ability as well, saying that "the Men of the Mark [[WillNotTellALie do not lie, and therefore they are not easily deceived."]] Indeed, Wormtongue does not use direct lies to trick Théoden, but rather lies of omission.
** Lying to Sauron is practically impossible. The only way to trick him is to plant seeds and doubts in Sauron's mind from afar. When Aragorn revealed himself in the palantir, he showed him Narsil but never once claimed he had the ring, but this act effectively led Sauron to come to that incorrect conclusion. This is actually Aragorn using Sauron's own tricks against him: Sauron himself only lies by implication, so he assumes that Aragorn is doing so as well.
** You can't lie to Gandalf either, as he demonstrates with Bilbo in the very first chapter (when Bilbo attempts to take the Ring with him to Rivendell: something that would be extraordinarily dangerous).
** It is physically impossible to lie to Galadriel unless you are magically stronger than her. Even lies of omission are impossible because she reads thoughts.

** Later in the series, other factions develop this capability, and duels of wits between Truthsayers can be every bit as dramatic as physical combat due to the multiple levels of IKnowYouKnowIKnow involved.
*** ''Literature/ChapterhouseDune'' explores life inside the Bene Gesserit sisterhood to a much larger degree than any other book in the series, with the Reverend Mothers basically always reading each other acting as 'watchdogs'.
* A rear-echelon officer in Creator/DerekRobinson's novel ''Literature/AGoodCleanFight'' has a rare form of synesthesia that causes him to smell rotten flesh whenever he is told a falsehood. This talent causes one of the secondary conflicts and leads to [[EverybodyDiesEnding the novel's abrupt resolution.]]
* ''Literature/TheNaturals'': Lia can always tell when people are lying, making her extraordinarily useful when [[FBIAgent interviewing suspects]]. She can't usually tell why they're lying, though — that's where our heroine comes in.
* Marlene Insigna from Creator/IsaacAsimov's ''Nemesis'', although her ability comes from intelligence and observation, not from any psychic power.
* Captain Mapstone in the novel ''Literature/GreenRider'' has this power, making her a valuable royal adviser. Unfortunately, this leads to life-and-death consequences when her ability begins to malfunction.
* Sandra from ''Literature/SuperMinion'' has this power. Half the hiring process for Hellion's Henchmen is her asking people basic questions like whether or not they're planning to betray the organization. Tofu would have gotten thrown out for being too young, except that he misunderstood the question and thought she was asking if he was at least eighteen ''days'' old.
* The ''Literature/{{Xanth}}'' series had two ''separate'' minor characters named Polly Graph. Both have this ability, but it worked in different ways.
** Dor's talent can be used that way; if he thinks someone is being untruthful, he can ask any inanimate objects on their person (clothing, jewelry, etc.) to verify.
* All Heralds in Creator/MercedesLackey's ''Literature/HeraldsOfValdemar'' novels have the ability to cast the Truth Spell, which detects lies. Those with more powerful mind magic can also cast the second-stage Truth Spell, which forces the subject to tell the truth.

* The most powerful mages in the ''Literature/SagaOfRecluce'' can tell if someone is lying since magic is based on manipulating Order and Chaos and lying is a chaotic act.
* Rashmika Els from ''[[Literature/RevelationSpaceSeries Absolution Gap]]'' by Creator/AlastairReynolds. She's also a ConsummateLiar.
* This is the purpose of the Confessors in the ''Literature/SwordOfTruth'' series. Their power made someone fall so deeply in love (to the point of destroying whoever they may have been before) that they would obey whatever the Confessor asked of them. One of their chief duties is determining if someone sentenced to death really committed the crime.
** Some sorceresses are shown to have that power. One of them is so eager to constantly say "Lie!", even about small things, that Richard mentions his friend must have had a very difficult time telling her his stories. Her response? "True."
* The Grand Veritable in Creator/AlanDeanFoster's ''[[Literature/{{Spellsinger}} Son of Spellsinger]]''. It was a sentient device that could not only detect all lies but knew the objective truth of any statement. And once you took it, [[ClingyMacGuffin you couldn't get rid of it]] unless someone voluntarily took it (though tricking someone into taking it worked) and it would always reveal the lies in every statement it heard, even lies of omission. This meant that it rather quickly became an ArtifactOfDeath.
* Flinx and Pip in Creator/AlanDeanFoster's ''Literature/HumanxCommonwealth'' series -- both are [[TheEmpath empaths]] and can detect lies as a basic ability. Flinx is human and knows how to be discreet about it (when he isn't holding the IdiotBall), but Pip (his [[ABoyAndHisX minidrag]] [[BondCreatures companion]]) is not and reacts very aggressively toward liars and anyone who threatens her or her master.
* In Sharon Shinn's books ''The Safe-Keeper's Secret'', ''The Truth-Teller's Tale'', and ''The Dream-Maker's Magic'', Truth-Tellers can detect lies ''and'' tell if a statement is objectively true, but are also incapable of lying themselves (to be fair, they tend to be honest by nature and not inclined to lie even if they could). At least once, a Truth-Teller stumbles on information -- that her friend's brother, presumed drowned, is alive -- by absentmindedly saying it and realizing that if she can say it, it must be true.
* Dûnyain monks in ''Literature/SecondApocalypse'' are so well trained in reading minute changes in people's facial musculature that they can practically look into a person's soul just by watching their face. Recognizing lies is a small part of what they see.
* Ayla, the heroine from Jean M. Auel's ''Literature/EarthsChildren'' series, can always tell the minute someone is lying. This is explained by her growing up with a group of people who communicate mainly through hand signals and body language, and thus she can tell by someone's body language if they are lying, even when she can't understand the language.
** Her entire adoptive species can do this, due to the nature of their language.

* Link, the BigBad in the Literature/BelisariusSeries, is a supercomputer from the future able to judge absolutely whether someone is lying. This is not the same thing as being able to judge whether they are being ''deceitful'', however, a distinction that costs it dearly.
* Vincent Katherinessen from ''Literature/{{Carnival}}'' by Creator/ElizabethBear. His lover is a ConsummateLiar.
* Kerrigan from the ''VideoGame/StarCraft'' novel ''Liberty's Crusade'', as a side effect of her [[PsychicPowers telepathy]]. [[BlessedWithSuck She hates it]], since most of the people around her lie constantly. She thinks [[TheChessmaster Arcturus]] [[ConsummateLiar Mengsk]] is truthful... and once she figures out he isn't?
-->'''Kerrigan:''' I ''looked'' I mean, I really ''looked'' into him.. That ''[[MagnificentBastard bastard]]''.
* ''Literature/TheDresdenFiles'':
** In ''Changes'', Dresden meets an FBI agent named Tilly, who can do this. This is actually magic-based, as Tilly has just enough power to tell if people are lying, but not quite enough power that he is clued into TheMasquerade (or even be aware his ability is magical).
** It's not exactly a lie detector, but wizards have a special ability called a soulgaze that allows them to look into people's eyes and see their inner self. It doesn't give specific information, but a deep understanding of what the person you're talking to is like and is capable of is a great way to work out exactly how trustworthy they are. It also only works once, so the information gathered is not necessarily going to be up to date, as people change over time. Of course, the soulgaze allows the ''other person'' to look into the Wizards soul just as easily, which can be helpful for building trust or quite problematic if it happens on accident.
* In the ''Literature/JohnDiesAtTheEnd'' sequel, Vance Falconer's ability to do this is what made him a famous detective.
* Kevin Groves in the ''Literature/SmokeAndShadows'' series.
* The [[BearsAreBadNews Pansebjörne]] from ''Literature/HisDarkMaterials'' are described as being capable of seeing lies and deception "as clearly as you see arms and legs". This [[ChekhovsSkill becomes important later on]]: [[spoiler:as Iofur becomes more and more human, he starts to lose his ability, leading to his defeat by Iorek.]]
** The Harpies have this ability and can use it to torment people. After the underworld is re-arranged, they ask for true stories from the dead in exchange for passage.
** Metatron had a similar ability to read the truth of someone's past. Using it on ConsummateLiar Mrs. Coulter convinced him that she would betray Lord Asriel and Lyra for him. Which was a lie.
* In Creator/RobertLudlum's ''Literature/TheAmblerWarning'', the main character has this ability.
* From the Franchise/StarWarsLegends:
** Force-sensitives have some insight into the emotional states of the people to whom they are speaking. They can feel when someone flinches or has an emotional reaction, even when those are carefully hidden. However, they have more trouble when the person they're speaking to is of an unfamiliar alien species, and it's ''very'' hard to tell if someone with a massive degree of self-control is lying. This is used the most in 'Literature/SurvivorsQuest'', during the GambitPileup in the first third of the book, when everyone is hiding something.
** Subverted in ''Literature/StarWarsAllegiance'', where the pirate leader called the Commodore floats in a pool with his eyes covered, the better to focus on the voice of his guest. He believes that doing this, damping down all of his senses but hearing, makes him more able to tell if he's being lied to and [[AwesomeByAnalysis pick out hidden things about the speaker]]. But he's trying to gauge Mara Jade, who is able to subtly stir the air and water to interfere with his senses without his knowing, and so he misses the fact that she's an Imperial agent sent to find connections between these pirates and corrupt officials.
** Gotals are a goat-like species with conical horns on their heads that allow them to sense electromagnetic fields, including those emitted by living creatures' neural networks. This makes them natural bounty hunters and diplomats, as they're not only able to detect their quarry, but sense subtle emotional changes that indicate someone's lying. It's not foolproof, though--in ''[[Literature/XWingSeries Wedge's Gamble]]'', Gavin Darklighter is nearly executed as a bigot after a Gotal sensed his relief that a Bothan woman stopped hitting on him at a bar. What he was mainly worried about was drawing attention to the rest of Rogue Squadron during a covert operation on the Imperial capital, and also he's just shy.
** Lorrdians are a race of humans who have developed a sophisticated language of signs and subtle face and body movements, due to their history of being slaves forbidden to speak. Many Lorrdians, including the BigBad of ''[[Literature/StarWarsRazorsEdge Razor's Edge]]'', Aral tukor Viest, can read truth and lies, as well as [[AwesomenessByAnalysis other aspects of a person]], off of his or her face and body. Facing Viest, Leia is extremely careful with both her words and her tone of voice and facial movements, trying to use ExactWords as much as possible to conceal her true intentions. When Han is captured, he does the same, but by then Viest knows more about them and their Rebel ties, and he is unsuccessful.
* The werewolves in Patricia Briggs' ''Literature/MercyThompson'' series are supposed to be able to smell when someone is lying (though for some reason this applies only to literal lies, rather than intent to mislead). As a result, the protagonist has a habit of telling the strict literal truth where possible.
** A very, very small number of werewolves learn how to tell lies to other werewolves: the trick is to convince yourself that you aren't lying, to buy into your own propaganda. Those few who figure it out keep the secret under heavy wraps, so as not to ruin the game for everyone.
* In Creator/TamoraPierce's ''Literature/CircleOfMagic'' universe, some "academic mages" have this ability. It's implied that it goes along with talent in other metaphorically sight-related magics, like scrying. Some mages who can do it are employed as "truthsayers" by courts and law enforcement (districts that can't afford one or an artifact equivalent use the old standby, ColdBloodedTorture). In her Literature/TortallUniverse, people with the Sight can tell when people are lying, among other things. The griffins from the same series take it one step further: lies cannot be told in a griffin's presence, and their feathers can dispel illusions.
* Powerful [[MakingASplash watercrafters]] in ''Literature/CodexAlera'' have this as a side effect of their [[TheEmpath empath]] powers. They can usually tell when someone's lying by monitoring their emotions, and while a [[ConsummateLiar very good liar]] can mislead or hide things from them, it's difficult to do. As such, [[MundaneUtility they're often called in as mediators in debates and trials]].
* March from ''Literature/TheSiranthaJaxSeries'' is a telepath, and this is the main reason he hates people. He always knows when they're lying, either to him or to themselves, and it's left him jaded about human nature.
* Una, the personification of Truth in the first book of ''Literature/TheFaerieQueene'', has the power to ''reveal'' the truth. For example, she couldn't detect that the old hermit who sheltered her and TheHero was the EvilSorceror Archimago or detect when he disguised himself as TheHero later, but when she deduced that Duessa's supposed messenger who crashed her engagement feast was Archimago in disguise, she was able to reveal his true form to everyone else.
* Literature/{{The Guardians|MeljeanBrook}} each have a unique [[PersonalityPowers Gift]] related to what they were in life. Hugh, who strove all his life to be honest, now can detect truth and force it from someone. It's deliberately activated by his love interest; when she can't bring herself to say "I love you" she says "I hate you" instead, knowing he will hear the lie in her words.
* Chane Andraso of the ''Literature/TheSagaOfTheNobleDead'' develops this power in the second arc.
* In Creator/KevinJAnderson's ''Literature/{{Blindfold}}'', the Truthsayers on the Atlas colony are a major pillar of the colonial society. They use a special drug called [[MeaningfulName Veritas]] to read people's minds and determine their guilt or innocence. All "readings" are conducted in public. All Truthsayers are DesignerBabies, trained from childhood to always tell the truth, especially when reading someone. They also receive training on being able to reasonably detect falsehoods even without the drug, the way normal people do it. This is more for failed Truthsayers who become Magistrates. The Atlas justice system depends on one axiom--"the Truthsayers are never wrong." Guess what happens in the novel?
* The Lord Ruler from ''Franchise/{{Mistborn}}'' has this ability, as a combination of his SuperSenses and having a thousand years to practice reading people. It doesn't hurt that he's a despair EmotionBomb, so that ''very'' few individuals can even muster the willpower to lie to his face in the first place.
* In Brian Lumley's ''Literature/{{Necroscope}}'' books, the British E-Branch eventually gets one of these as their leader. Ben Trask's psychic ability is to [[BlessedWithSuck instinctively]] detect lies. The only thing that might foul it up is if the person is telling the truth--as they know it. To him, it comes out as "true... but odd, somehow." Ben has also expressed great disgust with political seasons.
* ''Literature/{{Twilight}}'': Maggie has this ability; Charles is an inversion, he can't tell the truth.
* In the ''Literature/{{Fever}}'' series, Christian [=McKeltar=] is born a Lie-detector, a case of BlessedWithSuck and constant annoyance to anyone near him.
* In the Jennifer Lynn Barnes novels ''Golden'' and ''Platinum'', Lexie James can see truth as if it were a physical property, allowing her to instantly determine the truthfulness or falsehood of any statement. This isn't limited to detecting lies, as it can also be used to determine the truthfulness of guesses and conjectures and also allows her to persuade other people to believe an otherwise dubious statement.
* [[TheEmpath Brennen Caldwell]] from the Literature/FirebirdTrilogy can identify lies, even over video calls, thanks to his exceptionally strong [[{{Telepathy}} telepathic abilities]].
* In the Literature/LordDarcy stories, the head of His Majesty's Most Secret Service has this as his unique Talent.
* In the web-novel ''Literature/{{Domina}}'', this is Laura's power. Except it only works on absolute lies ([[MetaphoricallyTrue half-truths]] explicitly slip right by), so everyone treats it as [[WhatKindOfLamePowerIsHeartAnyway useless]].
* In the ''Literature/WearingTheCape'' series, a secondary character known as [[MeaningfulName Veritas]] has the ability to detect the truth of anything, whether spoken, written, recorded, etc. This proves a vital plot point when he allows the main character to determine who the real villain is via a phone conversation.
** It's later revealed that [[spoiler:he can only tell if the speaker/writer ''believes'' a statement is true or not, not whether it is factual. This allows him to be subverted by the Dark Anarchist, who honestly believes what he's doing is necessary for the future of humanity.]]
* [[OurDragonsAreDifferent Kantrishakrim]] of ''Literature/TalesOfKolmar'' appear to have this skill, somehow "smelling" when someone lies.

* Treecats in the ''Literature/HonorHarrington'' universe have this as an ability based on the fact that they're telepaths and empaths. The combination makes it quite impossible for someone to lie to them. Honor eventually develops a very similar if not quite as well-rounded ability.
* In Creator/JohnCWright's ''[[Literature/CountToTheEschaton The Hermetic Millennia]]'', Soorm tells Menelaus that he can do this. Menelaus counters that it's a pity so useful an ability failed to work.
* One aspect of a shamai's mental powers in A.L. Phillip's ''Literature/TheQuestOfTheUnaligned''. A minor plot point hinges on this, as the world's most powerful shamai verifies the Quest's otherwise unbelievable story.

* In Terry Mancour's Literature/TheSpellmongerSeries the short story "the Road to Sevendor"'s protagonist Lesana is a mage whose powers compel those around her to tell the entire truth, against their will. To say she is BlessedWithSuck is an understatement, in fact her desire to have her "curse" removed is the motivator for her short story.
* ''Literature/{{Lensman}}'': This is one of the abilities conferred by the Lens of Arisia. Virgilia Samms, who does not have a Lens, can also do it by reading tiny involuntary muscle movements; it is noted that her lack of need for apparatus makes her better at certain types of undercover work than actual Lensmen of the same period.
* The Daniyelan Truthspell in ''Literature/TheChildrenOfMan'' takes the form of an orb of orange fire into which the subject must insert his hand. As long as he remains perfectly truthful, he won't be burned. Should he lie, however... There is also a more difficult version that can force the subject to answer the Daniyelan's questions.
* The Trout Of Truth in the ''Literature/MonsterHunters'' series has this ability and will eat (and then spit out) anyone who lies in its presence. Very unusually, it senses not whether the subject ''believes'' what they're saying is true, but whether it actually ''is'' true. This leads to its use as a way to sort out new Hunter cadets into Banishers and Nethermancers. You stand on the shore of the Lake, shout out "I am a Banisher!". If the monster eats you, you're a Nethermancer. If it doesn't, you're a Banisher.
* In the ''Literature/ParadoxTrilogy'', Copernicus Starchild's psychic powers allow him to know when someone is lying to him.
* ''Literature/TheTiesThatBindHayes'' has this as a standard ability as members of the Inquisition. ''No one'' can lie to them. However, they can use ExactWords to answer questions truthfully. It's also an addictive power.

** In the television series adaptation, Mr. Curtain has cultivated this ability and when Reynie says that he's not working with anyone, recites back the list of physical signs to him that explain why he's lying, including the syncopated breathing, the perspiration on his forehead, the darting of his eyes, and ever so slight dilation of his pupils.
* ''Literature/{{MARZENA}}'': Marian is said to smell lies with her eyes. It's all about reading body movements, apparently.
* In ''Literature/DoraWilkSeries'', Witkacy's shamanistic abilities apparently let him discern whether someone lies, tells a half-truth or complete truths.
* Collette, a character in ''Literature/PlayingForKeeps'', has an interesting variation of this power. She possesses the superhuman ability to intuitively know a person's favorite food, making her a SupremeChef extraordinaire. However, this skill also makes her able to instantly tell if someone is impersonating someone else--even if they change their entire appearance, they can't cover up their culinary preferences.
* In ''Literature/AlienInASmallTown,'' the alien Jan have superhuman hearing and can pull this stunt by hearing a human's heartbeat. The genetically engineered Tesks, meanwhile, have a superhuman sense of smell and are masters of reading body language.
* In ''Literature/TheBalancedSword'', priests and other god-touched types are sometimes granted this ability by their patron god. It takes a lot of divine energy, and isn't always dependable, as it can be diverted or blocked by an antagonist force of comparable or greater power.
* In ''The Little Ships'', Literature/AlexisCarew encounters a Hanoverese intelligence officer who sees through both of her cover stories immediately just from his own experience as a professional liar. He first spots her as a New Londoner because of her accent, then reads the emotion in her voice to see through her lie about why she sought out the culturally French Hanoverese Lieutenant Delaine Theibaud, even approving of her attempt to make the lie seem convincing by including elements of truth in it.[[note]]To wit, she ''did'' join the Navy because of an inheritance issue with her grandfather's estate, but her grandfather agrees with her and wants to change the law so she can inherit, and she ''did'' [[AMatchMadeInStockholm fall in love with Delaine while held as a prisoner of war]], but came looking for him for military reasons.[[/note]]
* The spider-priests from ''Literature/TheDaggerAndTheCoin'' have this ability, as well as on the flip-side a CompellingVoice that causes anyone who listens to them to believe their words are true. However, this is ultimately deconstructed, because the spider-priests ability doesn't actually detect ''truth'', just ''certainty''; you can utter falsehoods to one of the priests all you want and so long as you ''believe'' it to be true, the priests' powers won't detect it. Furthermore, they're not immune to their own Compelling Voices, and so over time come to believe their own opinions represent objective truth. If you say something that goes against a spider-priest's beliefs, but genuinely believe it to be the truth, they'll be psychologically unable to reconcile the situation and will fly into [[BerserkButton an irrational berserk rage]].

* Truthwitches of ''Literature/TheWitchlands'' can instantly tell whether a person is speaking a truth or a lie. They can also tell whether a person is "true" or "false" -- for example, false if they're hiding something.
* In ''Literature/TheSorcererOfTheWildeeps'', Demane can tell whenever someone is lying thanks to clues that he takes in [[TheNoseKnows through his superior sense of smell]].
* Tattletale of ''Literature/{{Worm}}'' is exceptionally good at reading people thanks to [[SherlockScan her superpower]], which makes it very difficult to lie to her.

* ''Literature/TheInfected'': This is the sole power of Martin Joabs, who is routinely pulled away from his work whenever the heroes desperately need to verify something. He makes a powerful combination with Christian Poures (a telepath) and Ellen Doer, who has the power to tell when a person has been abused, coerced, mind-controlled, or had their memories tampered with.
* ''Literature/VillainsByNecessity'': Kaylana has this talent, presumably due to being a druid. It does have drawbacks, such as lies of omission, and non-verbal communication.
* ''Literature/LieToMe'' by David Martin: A detective can always tell if someone is lying. He goes to investigate a reported suicide, and doesn't doubt that it was suicide, but is certain that the dead man's young wife is lying when she says that she doesn't know why he did it. [[spoiler:The dead man took it badly when his wife told him that [[SurpriseIncest she was his long-lost daughter]].]]
* In ''Literature/{{Endling}}'', the main character is a "dairne," a walking, talking dog whose species possesses the unique ability to detect the lies of others. They can hear it from the person's voice -- the main character Byx describes hearing a lie as being like hearing a cat barking. In the story, she's been declared the [[LastOfHisKind last of her kind]], which would make her ability extremely useful to anyone who would take advantage of her. It's complicated, however, by the fact that her species has been declared extinct. Also, because dairnes can detect lies, some believe that they themselves are incapable of it. This is false, though it's true that they don't lie among their own kind, as it would be pointless, and thus aren't in the habit of it.
* This is, essentially, the role played in courts by ghatti in the ''Literature/GhattisTale'' series, to sit in on hearings and speak up (through a telepathically bonded human interpreter) when a witness attempts to lie. They actually had some difficulty understanding the concept of a lie at first, as they are incapable of lying, most likely for the same reason as the Clan in ''Literature/EarthsChildren'', namely, they have a gestural language, in which lying would be impossible.
* In "The Mind's Construction", one of the ''Literature/GeorgeAndAzazel'' stories, a SuperGullible detective ends up as one due to becoming more sensitive to gland output. Raises his status... causes problem with his girlfriend.
* In the ''Literature/CormoranStrikeNovels'', it is said in ''Literature/TheCuckoosCalling'' that Strike can smell a lie. He certainly doesn't he any supernatural abilities or anything, but he's more than experienced enough that if the signs are there, he ''will'' detect them. It basically takes a serial liar / psychotic type who is able to lie without giving off any of the usual signs to pull the wool over his eyes, as seen in ''Literature/TroubledBlood''.
* In ''Literature/FirebirdLackey'', Ilya suspects Mother Galina may be one (he's certainly never been able to lie to her) and fears that the Katschei might be one. [[ChekhovsSkill His experience in getting around the former helps him considerably with the latter]].
* In ''Literature/TheSilenceOfTheLambs'', Hannibal warns Clarice "don't lie, or I'll know". She never tests him on it but seems to assume he can.
* Eddie from ''Literature/TheSpeedOfSound'' can always tell when someone's lying. He makes a buzzer sound when people say things that aren't true, although Dr. Fenton tries to discourage him from doing it.
* ''Literature/HiveMind2016'': Downplayed with Lucas. Part of his imprint involves being able to read a person's reactions, so he can generally tell when somebody is lying. This is more of a problem than an advantage, as Amber can more easily tell if somebody is lying by reading their thoughts, but Lucas can use this on Amber when she knows something that he shouldn't.
* ''Literature/{{Quarters}}'': A trained bard can tell from the tone of a person's voice whether they're lying or not. Due to this, along with an ability to [[CompellingVoice compel]] [[TruthSerum truthful testimony]], bards supervise court trials.
* In ''Literature/AndThenITurnedIntoAMermaid'', Melissa's merpower - the unique ability all merfolk have that only works when they're in mer form - is the ability to tell when someone is lying.
* ''Literature/MedievalSeries'': Protagonist of second book ''Forbidden'', Amber has this ability as long as she's touching the person who's speaking, and she appears in the next book, ''Enchanted''.
* In ''Literature/MermaidsSong'', some merfolk have the ability to taste others' emotions on the water, including whether someone is lying.
* In the ''Literature/MermaidsOfErianaKwai'' trilogy, merfolk have enhanced senses that sometimes allow them to detect lies by feeling the changes in each other's pulses through the water.

* Agent Henry from ''Literature/{{Curveball}}'' can just tell if you're lying or not. Furthermore, if you're making eye contact with him, you lose the ''ability'' to lie at all.