A character with the ability to always know when someone is lying. Sound lame? Other characters who have to spend at least five minutes in their presence don't think so.
It may be the natural ability of an alien or some other non-human species, it may be a super power specific to one human, or it may be the effect of some Applied Phlebotinum. Could also be a prominent fringe benefit of a broader power like telepathy.
Some characters get the added bonus of being able to force people to tell the truth (as opposed to just remaining silent) rather than just detect deception.
In some situations, this becomes a Blessed with Suck power. The character can't disable it, so they know whenever anyone is lying to them, driving the character nearly insane from all the lies.
It can also be a learned ability, making this Truth in Television. This is because most people fidget, look away or do something else when they lie. So if a character is a Living Lie Detector, (s)he could just know what to look for. A police officer being able to tell when a witness is lying after years on the force is a common example of this.
An exceptionally self possessed and clever liar can sometimes be unreadable or even fool the Living Lie Detector. A particularly Genre Savvy character may exploit a weakness of the detector: he does not detect "the" truth, but if the tested subject considers something to be true or not. Which is not a minor point: if the villain tells a lower mook that the Doomsday Device has been destroyed, and this mook is exposed to the lie detector, he will say it was destroyed and the detector will check "True!"... and, in the meantime, unknown by the heroes and his own mook, the villain still has the Doomsday Device.
One aspect that goes alongside requirements for the mundane, non-PhlebotinousLie Detector polygraph, is that there are certain elements that need to be in place for a person to register the normal signs of a lie. One being a baseline observation of the individuals behavior, someone who is naturally jittery means slight twitches don't really mean anything. Another is a threat of punishment, if you're not worried about consequences then you're either not afraid of the truth or you have nothing to lose.
Characters with this power are also highly likely to see through or uncover The Masquerade because of the power.
See also Pinocchio Nose, You Can Always Tell A Liar, The Tell. Exact Words 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.
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A commercial campaign for Atlantic City centers on people who cannot seem to let go of behavior they picked up in Atlantic City. Hilarious, no? One includes a woman overhearing her co-worker announce she is going home sick. Our protagonist gets a look of pure epiphany on her face and says "She's bluffing."
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Nunnally Lamperouge/Princess Nunnally vi Britannia from Code Geass, a blind young girl who has gained the ability to tell if someone's lying to her (presumably to being able to sense pulse rate, transpiration or body temperature changes), if she's touching their skin.
Volume 4 of Code Geass R2 novel explains the origins of Nunnally's ability. Marianne conducted experiments with her own egg, giving Nunnally some powers derived from C.C. which allowed Nunnally to detect lies. The novel also reveals that it was Marianne's idea to blind Nunnally because Marianne had thought had removing one of the five senses would strengthen Nunnally's ability, which Marianne determined wasn't powerful enough.
The R1 anime also has a few scenes that imply Nunnally's abilities aren't restricted to merely lie detection - she can seemingly sense Code Bearers. Or perhaps NOT sense, as it's a Geass derived ability, that only C.C. and V.V. would be immune to, thus explaining why she mistakes one for the other. There's also that she detects Lelouch arriving in an earlier episode, well before he gets close enough to open the electric door.
Holo from Spice and Wolf claims that her wolf ears can tell if a person is lying or not most of the time. Given her lifespan and her inability to track down exactly what was being lied about in the first example, this is probably just a learned skill of knowing what to look for.
Karin from Naruto can notice someone's chakra being disturbed when they lie.
One of the advantages of Melody's powers in Hunter × Hunter is to detect lies with her supersensory hearing. If she hears your heartbeat go abnormal just a bit when you say anything, she can tell if you're lying or not.
Some incarnations of Astro Boy have this ability (though you couldn't really call him alive in any biological sense of the word).
Joe from Soul Eater was this due to his advanced soul perception. It's said to be the reason he broke up with Marie - he feared 'seeing through' her as his perception increased - and is likely why he worked with Shibusen's Internal Investigations. Highly likely Maka's own advanced soul perception will go this way.
The main character of the manga Kimi ga Uso o Tsuita gains the ability to detect lying after she gets into a car accident.
Ranma 1/2: This is only one of the reasons why Ranma Saotome thought Satori was annoying. It only made matters worse when Ranma realized that the kid was using his Telepathy to get back at him, because he was upset over Ranma and Akane's engagement.
Asashi Yuki from Iris Zero sees a devil tail growing out each time someone is lying. Because people around her were doing this all the time, she isolated herself from the others. Toru showed her that people can also lie not to hurt somebody or to protect their secrets. Thanks to his help Yuki opened herself up to the others once more.
This is one of the powers Violet's Devil Fruit granted her in One Piece. Because she can see through people both literally and figuratively, she can easily read people's minds and memories, making it obvious to her when a person is lying.
Wonder Woman, thanks to her enchanted lasso, is probably one of the most well-known examples. The Lasso is able to force people to tell the truth, as mentioned above - it takes godlike willpower to prevent this, and the subject will not be able to lie, only avoid saying anything at all.
As she is the living embodiment of truth, being around Wonder Woman at all makes people slightly more truthful but this effect is easier to resist than being in contact with her lasso.
As Mercedes Lackey pointed out in her introduction to "The Circle" trade paperback, the lasso doesn't just make its captive tell the truth, it makes them see and confront the truth.
Wonder Woman's creator, William Moulton Marston, also basically invented the polygraph ("Lie Detector").
Wonder Woman's sister Troia also has this ability, but in a lesser form.
Daredevil exhibits a similar ability using his superhearing to detect heartbeats, proving useful both in role as a superhero and double life as a lawyer. He's not perfect, however, and there's been a couple of occasions where a pacemaker has entirely thrown him off.
Doctor Strange, the Sorcerer Supreme, holds an amulet called the Eye of Agamotto which reveals the true nature of things. On one occasion he used it to compel a confession from a burglar. This happened in She-Hulk's comic, which at the time was a semi-comedic superhero legal drama: the firm tried to get the confession thrown out, since Strange had violated the fifth amendment protection from self-incrimination.
Wolverine from X-Men. He does not have it as an innate power, but his senses are sharp enough that they can spot 'tells'. When the X-Men were hunting down Cable, wrongly accusing him of having assassinated Professor X, Cable got out of a fight by saying to Wolverine "I did not shoot Xavier". Wolverine's senses correctly told him that Cable was being truthful.
In Top 10, everybody has powers (or gadgetry) that would usually make them a superhero. Duane "Dust Devil" Bodine's mother is the human lie detector, which is one of the reasons he doesn't like to deal with her.
Rorschach of Watchmen seems to discern truth from lies by means of listening to the tone in people's voices. However, due to his unsavoury techniques, it's equally likely that he discerns truth from lies by seeing whether you're still saying it after he breaks your fingers.
Although the first one could still be true, as he fully believed Viedt killed half of New York just from hearing him say it.
Superman has some ability to detect lies (among his many other powers) thanks to his enhanced senses. With him being Superman, the problems he faces aren't usually as small as someone lying...
But it IS pretty handy for a reporter.
One Donald Duck story features the duck family making friends with an alien who is allergic to lies.
Maggie is a witch and her power tells her when someone is lying. The audience doesn't know how yet, but we do know that that's how it works, because when Bella was immune, Maggie assumed she was telling the truth all the time.
Elspeth inverts the trope two ways. First, other people know when she's lying, and second, her power goes off when she's telling the truth—but its absence is notable.
Fear in the Metal Gear Solid 3 fanfic The Joy Of Battle is a human lie detector. He explains it simply to Sorrow after finishing his sentences for most of a scene: "I'm perceptive."ow
Changelings in You Obey have the innate ability to detect deceit, no matter well one attempts to conceal it. When Shadowfax is interrogated by a changeling and she tries pushing her luck, things go downhill in a hurry.
Applejack in the Pony POV Series becomes this after looking into the Truth, becoming able to see through lies and make people shy away if they're lying by looking into their eyes. Not even Princess Gaia's Lotus-Eater Machine can fool her.
Dark World!Rarity, being a fully awakened the Element of Honesty, can detect lies as well. Dark World!Applejack also has it, due to being the Element of Deceit, allowing her to detect lies as well.
A classic ability of the Hyuuga clan in Naruto fanfic; there's some basis in canon, but not to the degree it's sometimes carried. One fic had Naruto immune to the ability by virtue of his training to become absolutely, perfectly still (for Sage Mode).
In Harry Potter and the Antiquity Link, Harry was forced into taking the test for becoming an Auror Leader and passed. He received several spiffy new abilities as a result, including the ability to sense when someone was lying to him.
Another Harry Potter fanfic, the Psychic Serpent Trilogy, has the snakes in its verse have this as part of their titular prophetic powers. Being Seers they can See things that will be, and also things that are, and thus they can discern lies. This also leaves them unable to lie themselves.
In the second book of the trilogy a character becomes a werewolf and uses their enhanced senses to notice things like blood vessels dilating in the eyes. While they have those enhanced sense from as soon as they contract lycanthropy, it's not until they happen to read an article about unconscious physical reactions to telling lies in a Muggle magazine they become a living lie detector.
The Powers Of Harmony: One of the abilities granted to the Bearer of Honesty is Truesight, which sees through all illusions, as well as being able to automatically tell when someone is lying.
Though any unicorn skilled enough can cast Truesight themselves, it's temporary and costs a lot of magic to use; the Bearer of Honesty is able to do so instinctively and for as long as they want.
The Nuptialverse subverts and lampshades the trope — as Applejack has apparently had to explain many times, being the Element of Honesty does not give her the ability to tell when somepony's lying, which is why she couldn't tell that "Cadence" was an imposer.
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.
In Memento, Leonard learned to do this before his injury while working as an insurance claims investigator. As such, it is extremely difficult to deceive him in a face to face conversation. Or so he believes.
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.
Little Fockers 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.
The Incredible Hulk. 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/The Hulk's location (and was currently regretting it, as The 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."
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 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 Mr. Brooks. A neat example in that he never talks about or tells anybody about this ability. It also primarily manifests through his Imaginary Friend Marshall. He's also secretly the 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.
Harry Potter: Voldemort "almost always knows when someone is lying to him." He's not super-sensitive or precognitive, just casual about boring into other's minds. Snape's pretty good at this as well, as is Dumbledore.
And there is another art for protecting oneself from lie detection. At the beginning of tome 6, you know that 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.
Denethor from "The Lord of the Rings" : Gandalf explains to Pippin just before meeting him that it is extremely difficult to deceive him, and dangerous to try, due to his Númenórean psychic super-powers. His son Faramir seems to have inherited this ability, as he is able to immediately detect when Gollum lies to him.
The Dune universe contains multiple examples of humans with this capability.
The Bene Gesserit develop latent psychic abilities in humans alongside Charles Atlas Superpowers; one outcome of this is "Truthsayers", people trained to detect lies. Some, like the Lady Jessica, can only detect the intent to deceive but are not able to reveal the actual truth. Some, like Paul, his sister Alia, and later his son Leto, can fully unmask any lies merely through observing their subject. This difference becomes a plot point in the first novel when Dr. Yueh manages to conceal his planned treachery from Jessica by leading her limited Truthsense on a carefully designed Red Herring, counting on himself being Beneath Suspicion due to supposedly unbreakable mental conditioning.
Other characters, knowing of the capabilities of Truthsayers, have developed defenses against their abilities, such as Make It Look Like an Accident and other forms of Plausible Deniability when they can't have it known that they explicitly ordered the death of a rival.
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 I Know You Know I Know involved.
A rear-echelon officer in Derek Robinson's novel A Good Clean Fight has a rare form of synesthesia which causes him to smell rotten flesh whenever he is told a falsehood. This talent causes one of the secondary conflicts and leads to the novel's abrupt resolution.
Marlene Insigna from Isaac Asimov's Nemesis, although her ability comes from intelligence and observation, not from any psychic power.
Captain Mapstone in the novel Green Rider has this power, making her a valuable royal adviser. Unfortunately, this leads to life-and-death consequences when her ability begins to malfunction.
The 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 Mercedes Lackey's Heralds of Valdemar 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.
Herald Myste has a truth-sensing ability that doesn't require use of Truth Spell.
Herald-Trainee Mags is also developing non-magical truth-sense.
The most powerful mages in the Saga of Recluce can tell if someone is lying, since magic is based on manipulating Order and Chaos and lying is a chaotic act.
This is the purpose of the Confessors in the Sword of Truth 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."
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.
Anasûrimbor Kellhus in Second Apocalypse is trained to read minute changes in people's facial musculature so that his knowing when people lie is only a small part of what he can see. This makes for a formidable Manipulative Bastard.
Ayla, the Mary Sue heroine from Jean M Auel's Earth's Children 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. (Not Truth in Television, as her Mary Sue intelligence contributes to this)
Her entire adoptive species can do this, due to the nature of their language.
Ed Exley in L.A. Confidential is so insanely good at reading people that it is said he sometimes cannot look at himself in the mirror.
Link, the Big Bad in the Belisarius Series, 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 which costs it dearly.
Vincent Katherinessen from Carnival by Elizabeth Bear. His lover is a Consummate Liar.
Kerrigan from the Starcraft novel "Liberty's Crusade", as a side effect of her telepathy. She hates it, since most of the people around her lie constantly. She thinks ArcturusMengsk is truthful... and once she figures out he isn't?
Kerrigan: I looked I mean, I really looked into him.. That bastard.
In The Dresden Files, all wizards have a special ability called a soulgaze that allows them to look into people's eyes and see their inner self. If a wizard looks into the eyes of someone particularly evil, it can scar him for life. However, it doesn't necessarily tell you whether they did something, but simply gives an impression of what sorts of things they're capable of. It also only works once, so the information gathered is not necessarily going to be up to date.
Although the soulgaze allows the other person to look into the Wizards soul just as easily. Even for a nice guy like Harry, seeing the depths of his soul is horribly disturbing, even to Muggles who can't process exactly why. Wizards have a particularly difficult skill of being able to look people in the face without actually making eye contact to avoid accidentally setting it off.
Also, 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 for lying, but not quite enough power that he is clued into The Masquerade.
In the John Dies at the End sequel, Vance Falconer's ability to do this is what made him a famous detective.
The Pansebjörne from His Dark Materials are described as being capable of seeing lies and deception "as clearly as you see arms and legs". This becomes important later on: 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 Consummate Liar Mrs. Coulter convinced him that she would betray Lord Asriel and Lyra for him. Which was a lie.
In Robert Ludlum's The Ambler Warning, the main character has this ability.
In the Star Wars Expanded Universe, Force Sensitives have some insight on 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 Survivor's Quest, during the Gambit Pileup in the first third of the book, when everyone is hiding something.
Subverted in Allegiance, 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 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.
The werewolves in Patricia Briggs' Mercy Thompson 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 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 Tamora Pierce's Circle of Magic 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, Cold-Blooded Torture). In her Tortall Universe, 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.
March from The Sirantha Jax Series 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 The Faerie Queene, has the power to reveal the truth. For example, she couldn't detect that the old hermit who sheltered her and The Hero was the Evil Sorceror Archimago or detect when he disguised himself as The Hero 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.
The Guardians each have a unique Gift related to what they were in life. Hugh, who strove 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.
In Kevin J. Anderson's Blindfold, the Truthsayers on the Atlas colony are a major pillar of the colonial society. They use a special drug called Veritas to read people's minds and determine their guilt or innocence. All "readings" are conducted in public. All Truthsayers are Designer Babies, 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 Mistborn has this ability, as a combination of his Super Senses and having a thousand years to practice reading people. It doesn't hurt that he's a despair Emotion Bomb, so that very few individuals can even muster the willpower to lie to his face in the first place.
In Brian Lumley's Necroscope books, the British E-Branch eventually gets one of these as their leader. Ben Trask's psychic ability is to 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.
Twilight: Maggie has this ability; Charles is an inversion, he can tell the truth.
In the Fever series, Christian McKeltar is born a Lie-detector, a case of Blessed with Suck 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.
In the Lord Darcy stories, the head of His Majesty's Most Secret Service has this as his unique Talent.
In the web-novel Domina, this is Laura's power. Except it only works on absolute lies (half-truths explicitly slip right by), so everyone treats it as useless.
In the Wearing the Cape series, a secondary character known as 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.
Treecats in the Honor Harrington universe have this as an ability based on the fact that they're telepaths and empaths. The combination makes it quite impossible for soneone to lie to them. Honor eventually develops a very similar if not quite as well rounded ability.
One aspect of a shamai's mental powers in A.L. Phillip's The Quest of the Unaligned. A minor plot point hinges on this, as the world's most powerful shamai verifies the Quest's otherwise unbelievable story.
Psych: Shawn has this ability as well as other talents and skills similar to this
The show subverts this when Shawn and Gus's older doppelgangers show up (5x06).
Female Suspect: The cops were just here, I told them everything I knew.
Shawn/Peters/Gus/Boone: You're lying. [Boone pulls his gun]
A short time later...
Peters: How'd you know she was lying?
Shawn: I'm a psychic, Peters.
Gus: How did you know she was lying?
Boone/Peters: She's a woman.
Smallville: Ryan, Clark's little brother figure who can read minds, and Chloe in one episode, after being exposed to the experimental Levitas which caused those around her to tell the truth. Neither worked on Clark.
One episode of The Adventures of Superman show from the 50s featured Clark Kent grabbing the wrist of a man on death row and 'feeling' whether or not he was lying about being innocent.
Kyle, and later Jessi, from Kyle XY both had the ability to tell when other people were lying.
This was an ability occasionally used by Isabelle in The 4400.
After the release of the promicin shot, this is an ability showcased in "The Truth and Nothing But the Truth". It was Diana's sister April who got this ability, and she eventually wound up working for the government.
Deanna Troi from Star Trek: The Next Generation, since she's an empath, apart from when it would be inconvenient for the plot, in which cases it is handwaved as either a temporary failure in her abilities or her inability to sense the emotions of a particular species. Notable for her ever-irritating catchphrase "I sense great deception."
Geordi LaForge could also tell, at least on humans, with his VISOR (enabling him to detect minor shifts in body temparature, pulse, and suchlike).
Bra'tac in Stargate SG-1 has the ability to detect Goa'uld brainwashing by looking into someone's eyes. He uses this to detect that Teal'c is lying about being loyal to the SGC. Notably, Teal'c had managed to fool trained psychiatric personnel hired to deprogram him before this happened. Bra'tac does it again later when the Jafaa council was being subverted by Ba'al, though it took him a bit longer.
Matt Parkman from Heroes can hear people's thoughts, and so also knows whether or not they're lying. As long as the person he's talking to actually thinks in English, that is.
And doesn't know he can read minds. Mrs. Petrelli was able to keep him out of her head with relative ease before he got mind control powers.
He can also only compare what the person is saying to what they're thinking. While that is enough to tell a liar in most cases, Noah Bennet once managed to trick him by thinking something that wasn't true.
As of episode 12 of season 3, Sylar also can tell whether or not people are lying, although unlike Matt, he can't dig around in the person's head for the truth. Ironically, Sylar's known to lie his way out of situations, but gets violent when discovering that he's being lied to.
Played with on the episode "The Wall" when Sylar believes Peter is a hallucination. Peter has to convince him that he's real.
Of all the unlikely people, Spike from Buffy the Vampire Slayer demonstrates a mild version of this on occasion. As Buffy says at one point, "I can't fool myself. Or Spike, apparently." Later on he easily sees through Willow's pretence that she is coping after Oz leaves. On Angel, Spike is the first person to suspect Eve of being up to something beyond being the Senior Partners' liaison.
In RoboCop: The Series, the title character ran a program to gauge how truthful the crooks he was holding up by the scruffs of their necks were being. The reading was usually numbers like 92.4% or 33.4%. The joke in one episode was that the reading was 100% because the suspect in question was scared out of his gourd.
One episode had a scientist use a functionally identical lie detector on a smooth-talking politician, and every single thing he said came back at 50%.
The same thing happened when Robocop was questioning an immoral lawyer. The readings kept fluctuating.
In early seasons of LOST, Sayid claims to always know when people are lying to him, due to his past as a torturer. He is able to tell that Locke is lying about the existence of the hatch, and that "Henry" is one of the Others. The fourth season has called this ability into question somewhat.
Agent Gibbs in NCIS is said in several episodes in the early seasons to be able to tell if a suspect is lying just by looking at their eyes.
Ziva also has a fairly finely-tuned sense of when someone is or isn't lying - especially if it's Tony.
Derek, Scott and mostly any werewolves on Teen Wolf courtesy of their Super Senses. They can tell lies through smell and quickened heartbeats. Also, sexual attraction.
Jim Ellison from The Sentinel has highly developed senses and can therefore tell if people are lying by checking if their heartbeat is speeding up or if they're sweating too much.
Lie to Me is about a behavioral scientist who studies facial expressions, body language, and so on to determine if people are lying. The rest of the main cast uses the same science, and one is a "natural" who can do it without training. The show is based on the work of real life psychologist Paul Ekman, but its accuracy and usefulness is exaggerated for the sake of fiction. Ekman advises using a high-speed video camera to detect microexpressions (as they last fractions of a second) and notes other explanations for microexpressions, whereas characters in Lie to Me almost always detect them with the naked eye and rarely address explanations other than lying.
Similarly, Patrick Jane on The Mentalist is shown to have these sorts of abilities; either by feeling pulses, or by outright hypnosis. He also has a trick where he deduces the location of hidden objects.
The short lived Lifetime Network series Angelas Eyes was also based around the same concept (detecting lies via body language).
Scorpius from Farscape can see energy signatures in living beings, which change when the subject is telling a lie. This allows him to act as a very effective torturer- unless the victim has the Scorpius neural clone present in his brain.
Plus there was the lobster-like creature that could detect "cognitive dissonance". Fortunately John Crichton was able to fool it by sending his "twin" who was able to truthfully say that he hadn't been running around doing things the local Ruler didn't approve of.
Scarrans have this ability too (Scorpius is half-Scarran), though it appears to be based more on actual Telepathy than ES reading. In one episode Crichton was able to beat this by telling the literal truth about how he was rescuing Aeryn because he wanted to have sex with her (he just didn't mention they were also co-conspirators).
Medium does this in one episode where Allison hears a buzzer sound in her head every time someone tells a lie.
Parodied on Curb Your Enthusiasm, where Larry believes he can tell if someone's lying just by staring at their face. The audience is left to draw their own conclusion about how effective his method is.
On an episode of Law & Order: SVU, a serial rapist/killer (played by Martin Short!) who enjoys pretending to have Psychic Powers in order to play with his victims' families is revealed to have trained himself to be a Living Lie Detector using FACS.
Det. Adrian Monk uses his uncanny ability to determine when someone is lying to not only solve difficult cases but also to ruin several of his assistant Sharona's budding romantic relationships.
Judge Judy claims to be this, and there's nothing to indicate that she isn't.
Sandra from Survivor seems to have the power to tell when someone's lying. When Johnny Fairplay pulled his infamous "dead grandmother" ploy, she saw through it instantly, even before The Reveal to the audience. Several times she comes across as The Cassandra, as voting against Jon in that particular challenge got her grief even from her own teammates.
One episode of Criminal Minds had the team meet a boy who'd been blind from birth and who claimed that he could tell if something was lying by putting his hands on their head when they speak. It wasn't clear if it actually worked, but it adds tragedy to scene at the very end.
On Warehouse 13, this is the "talent" of the newest team member Steve Jinks, who himself is a terrible liar.
It can be beaten with an artifact, however, said artifact being Richard Nixon's shoes (which cause extreme paranoia in the wearer). It also doesn't apply to detecting false accents.
On Once Upon a Time, both Emma and Henry seem to have this talent. Emma invoked it in the pilot, asking if Henry's adopted mother really loved the kid. Regina's answer apparently didn't fly past Emma's radar.
Although, Emma has been fooled/mistaken a few times. Word of God states that Emma's emotions compromise this ability.
In season 3, when Wendy Darling is lying about not knowing where Henry is, everyone is fooled, even Emma, except Rumplelstilskin.
Seeley Booth seems to have this knack, at least in formal, interrogation settings. In one episode, he gets seriously rattled when someone else catches a suspect in a lie that Booth missed — Booth worries that his recent health problems have cost him his ability.
Dr. Sweets can detect lies, although his ability is based on his studies, rather than natural instinct.
Steven Bloom on Undercovers actually had "the Living Lie Detector" as a nickname from his CIA days.
One episode of Law & Order: Criminal Intent had a gambling-savant Man Child as a possible accomplice in a murder case. He was eventually cleared, but when he was shown video of his partner giving an alibi, he could see that he was lying, having an extremely acute ability to detect people's "tells".
In the comedic French series Hero Corp, where the characters are superheroes with decayed or mostly useless powers, Doug's power is freezing stiff whenever he hears a lie. This led him to quit his former job (a lawyer).
Myths & Religion
The legendary Irish sword Fragarach forced everyone to tell the truth if held at their throat.
Though, to be honest, most people would tell the truth if ANY sword was held at their throat.
More like people will say whatever the holder of the sword wants to hear.
Almost every game line in both the Old and New World of Darkness lines had some power that allows the player to know if someone is lying.
Noble members of the Sidhe House Gwydion, part of the Seelie Court, in Changeling: The Dreaming had the inborn ability to always sense when someone was lying or speaking an untruth. (Unless blocked by Unseelie magics.) This meant they were usually honest themselves. This would have made them a natural choice for the role of judges, if their House had not also had this tiny problem with suffering from bad temper. A pissed off Gwydion Sidhe knight determined to smite a filthy liar was someone to avoid.
The best was Demon: The Fallen, where demons could not be fooled by any form of supernatural trickery or illusion. Period. Mundane lies on the other hand could sail right past them.
The Seraphim, a flavor of angel in Steve Jackson Games' angel-and-demon RPG, In Nomine (and the French RPGs on which it is based). They are fundamentally attuned to the objective truth of the universe and can spot lies instinctively (sometimes even spotting not just what's a lie, but what the actual Truth behind it is). The downside is that every lie they tell moves them closer to believing that anything they say must be true, at which point they Fall and become the setting's demonic Liar Liars, Balseraphs.
GURPS has the Empathy advantage and the Detect Lies skill, which are also synergistic - having Empathy gives a bonus to Detect Lies.
Phoenix, in the second and third games, is indirectly this thanks to the Magatama one of the Fey family gives him. It can detect when someone is hiding something from him and show how much are they willing to hide the truth via "Psyche-Locks", which break when he starts piercing through the truth. That said, it's not flawless: A poorly worded question can make someone slip past its effect, and as one particular case showed, cause more than a few problems.
The title character of the fourth game, Apollo Justice, is very good at spottingCharacter Tics, so he also has elements of this. Like Phoenix with his Magatama, Apollo relies on his Missing Mom's large bracelet. The tics don't always manifest, so the ability is not massively reliable.
As is Apollo's half-sister Trucy Wright, only she doesn't have the benefit of Apollo's bracelet.
Marvin Grossberg has the amazing ability to tell if somebody is lying.... through his hemorrhoids.
Aya: (No, no, I'm a tengu pretending to be a human. There's something I needed to look into ... ) Yuugi: You know, I really hate good Tengu lies like that. Aya: (I'm so very sorry. I didn't mean to come down here to spout lies to you.)
The Spider Cliff Mysteries: Rebecca's witchy abilities allow her to tell whenever someone is lying to her, which should be extremely useful in a mystery, but situations always interfere so it has never solved a case.
Gail Curmen, one of the two main characters of Thunderstruck has this ability. Not that it does her much good — one of the main motivations of the plots of the assorted villains is a matter of opinion.
Biscuit in Goblins is a justified instance, due to the Goblins universe being governed by Dungeons & Dragons mechanics; Sense Motive (the skill which lets you know when someone is lying) is based off a characters wisdom, and creatures gain a bonus to wisdom as they age. Biscuit, being over 600 winters old, has a considerable bonus to his wisdom....
Fey of the Whateley Universe is a powerful empath and can use that to tell what people are feeling. Chaka can do the human lie detector bit too, but she does it by reading their Ki (naturally).
Chakats (due to all of them being empaths) and Redpaw skunktaurs (telepaths) in the Chakona Space setting are all about this trope and employ it on many occasions.
Kelly from We're Alive is able to do this from her background as a lawyer. She's able to detect when one of the Colony members is lying, allowing her to save Pegs and Michael in time to escape Gatekeeper's coup. She is less able to get a read on Pippin though, because his face was so badly swollen from the beating the Mallers gave him that she couldn't read his facial tics.
Tattletale of Worm is exceptionally good at reading people thanks to her superpower, which makes it very difficult to lie to her.
Avatar: The Last Airbender: Toph; it's a Disability Superpower 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. It didn't work on Azula, who lies as easily as she breathes.
Azula: Are you sure? I'm a pretty good liar. I am a four hundred foot tall purple platypus bear with pink horns and silver wings.
Toph: Okay, you're good. I admit it.
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 which they then only re-enforce by attempting to deny it.
Toph's case is unusual in that she doesn't have special psychic or empathic powers, rather she determines whether someone who isn't a total sociopath is lying in the same way an actual Polygraph Machine does in real life, a literal Living Lie Detector Test.
In the Superman: The Animated Series episode, "The Late Mr. Kent". In it, Clark interviews a man on death row who claims he is innocent. Clark uses his super-hearing to measure the man's heartrate and his super-vision to check the man's eye movement, and both remain steady, indicating that he is telling the truth. However, Superman does not take that as conclusive evidence, but just as something that prompts him to investigate the story further.
In the second season of the Spawn HBO animated series, the character Merrick is able to tell when someone is lying by the hesitation and inflections in their voice.
The magic artifact harp from the DuckTales episode Raiders of the Lost Harp would say in singsong "fibbing fibbing fibbing!" in response to any lie heard in its presence.
Parodied in Phineas and Ferb" with Albert, "the ta-ruth'' detector." Because he's "impossible to fool", his brother worries that an incredibly lame plot to trick him involving a hologram and some Paper Thin Disguises will fall flat on its face. Turns out that Albert believes anything you tell him.
Albert: So tell me about this Eiffel Tower.
Baljeet: Well, it's big.
Buford: And Mexican!
Albert: I thought it was French. Whaddya know, learn something new every day.
The Alchemist from The Venture Bros. can tell whenever someone is lying. It's not always as useful as you'd think however, as he quickly discovered when trying to assist Hank with his "case" of Dermott's missing sister (who as it turns out was just stuck in traffic). They discover a deeper mystery brewing under the surface, but Al can't make heads or tails of the conflicting witness accounts because none of them adds up and yet no one is lying. He was simply missing a single but critical fact: Dermott's "sister" was really his mother who had given birth to him as a teenage pregnancy, and the woman whom he thought to be his mother was his grandmother who had orchestrated the cover-up. Dermott's father is really RUSTY.
Scott Adams, creator of Dilbert, claims his training in being a hypnotist gives him the ability to tell when most people are lying.
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 lasts 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 Real Life is 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 confirm 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 would ever so much as twitch.
Then there's the matter of people whose body language and/or emotional responses don't fit the human norm, e.g people with a variety of personality and/or mental disorders.
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.
Inversion: 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."