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Lie Detector
And you think your in-laws are embarrassing...
Now, studies do show that polygraph tests are slightly better than, say, marshmallows at determining a person's truthfulness, but they are far from completely accurate.
Cracked

The typical Hollywood Lie Detector is not like a polygraph. It is instead equipped with red/green lights or a loud buzzing/dinging to indicate truthfulness, which it decides accurately and instantly. The victim is usually betrayed by the machine to comic effect.

While Perp Sweating an especially naive criminal, the cops may employ a fake lie detector, often a photocopier with an ominous paint job. The device really is a photocopier, secretly loaded with pages that have been preprinted with the words "TRUE" and "FALSE". The cops use the machine's answers (sometimes along with a warning that this is a new and experimental model of lie detector that could cause cancer or erectile dysfunction) to exasperate the perp into a confession. (Note: some people claim this has happened in real life, but Snopes has its doubts.)

It should be noted that polygraph results are not necessarily reliable on their own; it requires more than just a few wires hooked up and asking a couple of questions. It involves a certain type of room, seating arrangement, several minutes of general questions to establish a baseline, a skilled professional to interpret the results and a specific situation where the target has a "reward or punishment" attached to the results. Even then, the accuracy is at "a level slightly greater than chance, yet short of perfection".

For almost all cases, real life polygraphs are simply "Unreliable, Unscientific and Biased", according to the National Academy of Sciences, their findings not being admissible in court. So, this is an Inversion of Truth in Television.

In fact, it would be more accurate to call a polygraph a "Truth Detector" rather than a "Lie Detector": when used properly, the device can not identify lies, but is much more accurate at providing evidence that the subject is being truthful. Polygraph results typically render not as "this statement is honest" vs "this statement is dishonest", but rather as "this statement is probably honest" vs "inconclusive".

Professionals also argue that the term 'lie detector' is misleading altogether because the actual purpose of the polygraph is to register certain involuntary reactions of the human body, not to interpret them. In other words, interviewer may only note that a particular question causes some unusual reaction but cannot really answer why it is so (e.g. the question 'did you drown the victim' may cause reaction because the suspect really drowned the victim or because he witnessed drowning of a friend and is still haunted by the experience). In real life, polygraphs usually help to narrow the range of possible leads to ones that appear most certain and require complex set of precise questions although you almost never see it in fiction.

Despite their proven unreliability, they are still given great weight by both the media and various governments.

Interesting note: The polygraph was invented by William Moulton Marston, who also created the character of Wonder Woman... who happens to wield a magic lasso that forces people to tell her the truth!

Compare with Living Lie Detector, when someone can discern falsehood as a superpower.

Examples:

    open/close all folders 

    Advertising 
  • A commercial for Energizer batteries features an Energizer scientist hooked up to a lie detector and the Energizer Bunny in a cage above a tank of piranhas. If the scientist told the truth about whether or not Energizer outlasted Duracell in digital cameras, the Bunny would be safe, and if not, the Bunny would take a dive.

    Comic Books 
  • Lie detectors in Judge Dredd function on the basis of red and green lights, though they can apparently still be fooled.
  • Superman once encountered an inquisitive college professor who began to suspect that one of his students was Superboy and started asking everyone if they were him as a demonstration for the workings of a lie detector. Superman avoided detection by realising he was no longer a "boy".
  • The 1980's British Starblazer comic had the Truth Meter and the Truth Sensors, but the latter took a long time to work.

    Film 
  • Subverted in Equilibrium, which uses a polygraph—not necessarily to detect lies, but to detect emotional fluctuations.
  • Used in great comedic effect in Meet the Parents (pictured above). Already intimidated by Robert De Niro, Ben Stiller was hooked up to the machine. When DeNiro asked, "Have you ever watched a pornographic video?" Stiller visibly stumbled through a "No" while the needles flickered about wildly.
  • The Voigt-Kampf test in Blade Runner - although that is more of an emotion detector.
  • Flash Gordon. While Princess Aura is being interrogated by Klytus, she is hooked up to a Lie Detector. When she lies a light blinks and a siren goes off.
  • Buckaroo Banzai. Lord Whorfin hooks Buckaroo up to the Shock Tower, which not only detects when Buckaroo is lying but gives him a shock when he does.
  • The Sentinel. Basically the first plot twist. Secret Service Agent Pete Garrison is blamed for treachery and has to go on the run because he failed a polygraph test. Why? Because he was scared they'd find out he's been having an affair with the first lady!
  • One character in Anatomy of a Murder has taken a lie detector test, but its results are not admissible in court.
  • The movie Sneakers plays this oh-so-straight. The sneakers improvise a lie detector out of an old Cradle Modem and some miscellaneous equipment. They attempt to hand-wave it by saying that it's not as good as a real lie detector because it can only test the stress in the person's voice(Note, that this is through a phone line, and into a device that essentally puts a microphone up to the earpiece), but it still seems to work perfectly and they trust the results implicitly.
  • In one of the Ocean's Eleven films, the team nerd has to pass a polygraph test as part of a scam, and spoofs the system by keeping a thumbtack in his shoe and pressing his foot down on it while answering the calibration questions.
    • Later in the same movie, the sophisticated computer systems can tell if a person was cheating at the games by reading various body signals. It is fooled when the rigged slot machine gives off the giant jackpot to a random woman who didn't know about the con.

    Literature 
  • The humorous scifi novel Who Goes Here? by Bob Shaw had a natural extension of this trope: a Mad Scientist, frustrated with the failings of lie detectors, designed a device to force the subject to tell the truth. It consisted of deodorant to stop him sweating, and devices to keep the subject's breathing and heart rates constant. It failed.
  • Appears in David Weber's Off Armageddon Reef as a piece of high-tech gear that looks like a glowing gem the protagonist recognizes but the locals regard as magical, with the color changing to indicate a lie. The protagonist very carefully phrases the answers to not set it off.
  • In the Stephen King novel The Waste Lands, Roland and company are on board a high speed train run by a sophisticated A.I. The A.I. informs them it can tell with great accuracy when they are lying by monitoring voice stress patterns.
  • The same thing happens in The War Against the Chtorr. During a therapy session the protagonist is told he's lying; he immediately jumps out of the chair he's sitting in. The therapist answers the unspoken question that yes there are polygraph sensors in the chair, but he can tell he's lying from the stress in his voice.
  • H. Beam Piper's Little Fuzzy series has the veridicator, which shows blue for truth, red for lies, and mixed patterns for half-truths. The veridicator is an accepted and vital part of the judicial system, to the point that trying to prove that it works on the Fuzzy race is a major plot point in the third book—otherwise they can't legally testify in court.
    • The veridicator is also used for an interrogation in Space Viking:
      "This is a veridicator. That globe'll light blue; the moment you try to lie to us, it'll turn red. And the moment it turns red, I'm going to hammer your teeth down your throat with the butt of this pistol."
  • Robert A. Heinlein's novel The Star Beast. A "truth meter" is used on witnesses during a court trial. When the subject lies, a needle swings into the red zone, a ruby light flashes, and a warning buzzer goes off.
    • Interestedly enough, a witness is telling all sorts of lies and the device keeps going off. At one time, she tells an obvious falsehood and it doesn't go off. The judge concludes that she really believes what she is saying...even though it patently is false. A limitation of even perfect (i.e. fictional) lie detectors.
      • This limitation is also discussed in H. Beam Piper's Fuzzy novels (see above); in-universe, lawyers like to make the point by telling the old saw about the lunatic who said he was God and the veridicator backed him up.
  • Also by Heinlein in his Between Planets the protagonist Don Harvey is subject to questioning by Venus Republic soldiers while hooked up to a lie detector after first waiving his rights about self-incrimination.
  • In Randall Garrett's story "The Best Policy," an alien race planning an invasion kidnaps a random human and hooks him up to a Lie Detector in order to get information. He manages to cleverly word his answers so as to give them the impression that humanity is insanely powerful and not to be messed with.
  • In the Incarnations of Immortality novel On A Pale Horse, Luna and Zane hold Truthstones (which glow when someone lies) while discussing sensitive personal matters.
  • Kurt Vonnegut's novel Player Piano includes a courtroom scene where the protagonist is hooked up to a lie detector with a large dial ranging from "False" to "True".
  • The Goblin Wood by Hilari Bell features an explicitly magical version of this; a bell that rings when a lie is told near it. This has its downsides, as indicated when its user is asked, "Are you sure this will work?" "Of course I'm sure—" Ding. Later, her captive turns the questions around on her, and in response to her Motive Rant asks whether her Actual Pacifist mother would appreciate the violent vengeance that has been taken for her murder. "If my mother was still alive, she'd be proud of me!" Ding.
  • In one of the Hitchhiker's Guide to the Galaxy books a witness is forced to tell the "whole truth" after being given too much truth serum. Sure enough, he begins spouting facts about everything the universe has to offer. It takes him several years.
  • The Heralds of Valdemar series has the Truth Spell, the only form of magic known to the Heralds between the death of Vanyel and Elspeth's becoming a Herald-Mage centuries later. The spell has two forms: The weaker form is a truth/lie indicator, the stronger form forces the target to tell the truth as they know it.
  • The Magic and Malice duology had a truth spell connected with a set of artifacts known as the Saltash Set. The spell used with the full set can compel a person to tell the truth. With an incomplete set of the artifacts, it just indicates whether the person is telling a lie or the truth (or if they're hiding part of the truth).
  • A truthspell is used in Simon R. Green's Hawk & Fisher, which forces people to speak only truthful statements. This attempt to find out who committed two murders fails, due to the murders having been committed by two different people, each of whom could truthfully deny having killed both victims.
  • In Snow Crash by Neal Stephenson the rump of the federal government (which pretends to still rule the USA) has its employees take weekly lie detector tests that may involve sedative drugs and NMR machines to detect activity in parts of the brain used for lying. It's a plausible technology for a reliable lie detector.
  • In William Brittain's story "The Artificial Liar," one of the guards at a government research center was gaslighting a file clerk who lived in the same boardinghouse as him so that, during the inevitable investigation after said guard had smuggled out some highly sensitive material, his chosen patsy would have extreme reactions to the polygraph questions.
  • The Katharine Kerr novel Snare has shamans who can smell whether or not a person is telling the truth. It works by detecting a person's emotional state through subtle changes in a person's scent (One of the talents held by the shamans is exceptionally sharp senses), and lying makes most people nervous. It's mentioned that this might not work against a habitual liar who would remain perfectly calm when deceiving others.
  • In Mercedes Lackey's Firebird, Ilya suspects Mother Galina may be one (he's certainly never been able to lie to her), and fears the Katschei might be one. His experience in getting around the former helps him considerably with the latter.
  • The Stainless Steel Rat beats being polygraphed by the secret police on a couple of occasions, once by working himself into an artificial state of panic before the test, then thinking boring thoughts during it. In another book he insists on a lie detector and is told the chair he's sitting in is one, causing him to think, "I'm glad I didn't know that when telling those other lies!" The Rat then proceeds to give a truthful but misleading statement that clears him.

    Live Action TV 
  • The Drew Carey Show:
    Mr. Wick: "Carey, you're one of our most valued employees." [buzz] "Well, maybe not, but I respect you a lot." [buzz] "You've got a bright future here..." [buzz] "Oh, will you get these things off me! I don't like being tied down like this!" [buzz]
  • Family Matters: Steve's lie detector has the added feature of giving Carl an electric shock if he doesn't tell the truth.
  • Murphy Brown: Murphy takes a buzzing lie detector test after she accuses a coworker of sexual harassment. Miles takes the opportunity to get Murphy to confess having switched his medical records with a guy from Accounting as a prank, causing the former to get an enema and the latter to get unnecessary stomach ulcer surgery.
  • An episode of Nikita has Alex hooked up to a "FMRI" it looks alot more like an ECG and is able to trick it through short and precise statements that are technically true. The problem is that to make such statements avoiding a lie would cause a lot more activity in the brain than such short statements would produce normally.
  • A strange alien lie detector appears on several episodes of Stargate SG-1, which is somehow capable not only of discerning when the person is telling a lie, but also when they're lying even if their conscious mind thinks they're telling the truth. Also, the comedic take was subverted in an early season 10 episode, where the tester is tortured:
    Tester: "By the way, I must say you're looking excellent today."
    Vala: Thanks, you look excellent yourself- [needle ticks rapidly] -I mean, very nice- [needle ticks rapidly] -that is, not objectionable- [needle ticks rapidly]...
    • However, the Za'tarc detector only detects concealment, not the subject being concealed. This distinction becomes important when Jack and Sam come under suspicion because they trigger the Za'tarc detector. It's not because they've been compromised, but because they're trying to conceal that they care about each other "way more than they should".
    • The operating principle of the Za'tarc detector assumes that (as was once widely believed in real life, but now has fairly little support) the human mind secretly keeps an accurate "recording" of everything it experiences, and therefore even an unknowing lie (and even, one supposes, an honest mistake) can be detected by comparing what is said to the infallible mental record. The device is related to the Mental Picture Projector technology sometimes seen in the series.
  • Gilligan's Island: The Professor builds a lie detector out of — what else? — bamboo and coconuts and tests all the men to find out who sent Mrs. Howell a love letter. One of the gags is The Skipper passing until he says, "See? I always tell the truth," which sets it off.
  • Avoided in Alias, which features a more realistic lie detector—that is to say one that doesn't explicitly say "Truth" or "Lie", but just provides raw data such as heart rate and blood flow in particular areas of the brain, requiring the interrogator to use his own judgment to decide on the truth of a given statement, and being much harder to fool. Then, outright subverted, when the difficulty of tricking the device almost gives away the protagonist, when after extensive training and practice with her handler her results look too perfectly honest during the real interrogation.
  • In the Jonathan Creek episode "The Tailor's Dummy", TV presenter Carla, who is preparing to host a talk show with a Lie Detector as the gimmick, uses it to prove to Jonathan she's happy in her marriage with the show's director. It announces she's lying. Later the director (who doesn't know about this) admits to Jonathan that it's completely random.
  • Maury Povich has devolved into using a lie detector on nearly every episode of his talk show (when he's not doing paternity tests or asking you whether she's a man or not...)
    • Steve Wilkos has as well.
  • The X-Files episode "Squeeze" uses a lie detector test to good effect, where the killer manages to fake his way out of the test quite effectively - except for two questions Mulder inserted implying the truth about his identity (that he was over one hundred years old and a human liver-eating mutant) that he most definitely was not expecting, which pinpoint the fact that he is lying. Of course, the other agents aren't willing to accept that he's one hundred years old and let him go anyway.
    • As the other agent points out, any innocent man would likely have had some kind of reaction to that question. Mulder might have had a better result if he'd asked Tooms about the victims he killed decades ago, using their names but giving no other details.
  • Averted in Seinfeld when Jerry takes a surprisingly realistic lie detector test to try and prove he doesn't watch Melrose Place. Instead of being asked directly, he's just asked to give his details before being asked a string of questions about events from Melrose Place ("Did Kimberley steal Jo's baby?" "Did Billy sleep with Allison's best friend?" etc etc). And instead of lights or buzzers or wildly jagged needles, the needles just jiggle a little when he answers, but not in any significant way. In the end he breaks down under the pressure of endless Melrose Place trivia and confesses, and we never find out whether he was beating the machine or not.
  • From back in da day, the lie detector was the plot point of an episode of Barney Miller, as an entire police division was being randomly tested (a procedure that was the Hot Topic of the Day in the 1970s). Det. Wojohowicz failed miserably due to being nervous and deliberately provoked, while Det. Dietrich passed perfectly (despite claiming to be from outer space) simply by remaining calm.
  • Star Trek: The Original Series had a Lie Detector hooked up to a computer in the episode "Wolf In the Fold" ... SUBJECT IS RELAYING ACCURATE ACCOUNT.
  • The sheriffs on Reno 911 frequently spend their downtime interrogating each other with the polygraph. Of course, the questions or responses invariably turn uncomfortably personal, and Hilarity Ensues.
  • Parodied in this sketch on Mr. Show; prospective employers are interviewing a job applicant and putting him through a lie detector test. They're soon flummoxed when the applicant - who answers everything in the affirmative - begins confessing to the most ludicrous things, including being addicted to every hard drug known to man, stealing 'space plans' from NASA, killing a man with his mind, and eating a train piece by piece after first derailing it with his penis. All the while, the lie detector is silent, indicating that he is telling nothing but the truth. Eventually, the employers - who are revealed to be the operators of a shoe store - give him a job, and the applicant claims that he loves shoes - BUZZZT!
  • In the short-lived sitcom Quintuplets, two of the brothers, Pearce and Parker, try to make a lie detector in order to find out which of the two their mutual crush likes better. Unlike most detectors, when someone lies, the detector makes toast. Pearce is the one to put the thing together, and tests it out on himself. He sets it up, and tells Parker to touch it. The detector gives Parker a (very painful) shock. Pearce tells Parker, "I had no idea that was going to happen." Toast pops out, leading Pearce to gleefully exclaim "It works!" Hilarity (and disaster) ensues.
  • There's one beneath the Buy More in Chuck, which they use to question a character about Fulcrum activities. Too bad Chuck didn't pay attention to the last answer...
  • The TV show Lie to Me, which bases its detection off people's faces, hates polygraphs. The characters point out that your reaction is going to be altered if say, a hot chick walks in and takes over the lie detector exam. Also that you might as well use a large egg being held in your hands as one, because if you are under stress and squeeze and break it, that could indicate that you're lying. In one episode, they show it's possible to beat a polygraph by taking a depressant to decrease your body's stress reaction.
    • In a later episode, they use a (fake) polygraph on a suspect who he knows is going to try to trick the system. The idea is that he'll focus on trying to trick the polygraph instead of the people reading his facial cues.
  • Used twice by Homicide: Life on the Street.
    "We're gonna neutron this son-of-a-bitch!"
    • Parodied in at least one case; the 'lie detector' turns out to be a photocopier that the detectives have loaded with sheets of paper with "LIE!" printed on them, which they use to trick particularly credulous suspects into confessing the truth.
  • The fifth season premiere of The Wire.
  • At least once on Law & Order.
    • The show alludes to its fallability and inadmissibility in court, at least.
  • As always, MacGyver did it. As always, it worked well enough to cause the villain of the week to give himself away. Notable components included an alarm clock and a sphygmomanometer.
  • Used in The Unusuals against a serial killer of cats. It appeared to be a Lexmark or Canon inkjet printer with the lid over the scan plate removed.
  • In RoboCop: The Series, Robocop was literally a walking lie detector. He used "voice stress analysis" to make instant, near-infallible truth assessments. The one time it failed was when interrogating a city councillor, who as a career politician was such an instinctive liar that every statement he made (even a baseline response such as his name) registered exactly halfway between truth and falsehood.
  • In the Torchwood episode "Adam", Jack uses the "best lie detector on the planet" (complete with green/red light) on Ianto, who has had false memories implanted. Since Ianto is convinced he's murdered 3 girls, no lie is detected ... but Jack still knows he's innocent.
  • The Commish. The title character knows that an informant is somehow beating the lie detector, and uses a Honey Trap to find out how. It turns out he's placed a thumbtack in his shoe, and is pressing down on it so as to give the same response each time. The Commish schedules another test, then has him walk up and down an endless amount of stairs under the excuse that the testing area keeps getting changed. Eventually the informant realises the game is up and removes the tack to give his by-now extremely sore foot a rest.
  • Battlestar Galactica. In a flashback to before the war, Adama is seen applying for a job in which he must take a lie detector test. One of the baseline questions (used to establish the reliability of the other questions) is "Are you a Cylon?" (This was before anyone knew the human-looking Cylons existed). In a further irony, the man administering the test is himself a human-cylon.
  • The Parkers: A lie detector watch zaps when the wearer tells a lie.
  • SeaQuest DSV has a police officer in one episode with a sneaky lie detector. He hands people a roughly pen shaped object, tells them it was found at the scene and asks if they have any idea what it could be. After they answer in the negative he proceeds to ask regular questions. The device is actually a lie detector which he owns and he is tricking them into holding it while being questioned.
  • The first episode of Lois and Clark has a polygraph that works this way. Clark's 'baseline' questions are 'Is your name Clark Kent' and 'Are you Superman'; he's supposed to say yes to both and get a 'lie' response on the second, and even though he's totally freaked out at saying it to the Superman-hunters, saying 'yes' he's Superman gets a no-lie flatline.
    • The hunters mutter "the machine is broken or this reporter is so mild-mannered he hasn't got a pulse," to make things more confusing, and funny. He sets it off by blowing on the needle with super-breath to get his no, then sets it off by saying he can't contact Superman. (Although it's fine with 'I've never met Superman.') Magic!
  • This old Johnny Carson skit on The Tonight Show involves a politician who agrees to be hooked up to one of these at a press conference, with the expected hilarity ensuing.
    "I feel my opponent is a decent man." [BUZZ!] "He's an okay man." [BUZZ!] "He's a man." [BUZZ!] "He's bisexual."
  • An episode of Tek War had a police detective use a combination lie detector/shock collar. If it detected a lie, it gave the wearer a painful zap. It's used once on a known criminal, who gives truthful information. Later it's used on a hotel maid that they suspected was concealing evidence. Despite her persistent denials, the device kept shocking her until she passed out.
  • In Pan Am Kate has to pass a lie detector test that she has to lie to in order to not incriminate herself regarding a man she shot.
  • In Psych, Lassiter uses one on Shawn with excuse that he's just testing whether the machine is working or not to figure out whether Shawn's secretly dating Juliet. The machine appears at first to be a typical hyper-accurate bit of Hollywood Science (registering an honest response when Shawn blurts out that he's in love with Juliet while hooked up to it), but promptly subverted when Lassiter follows up with the question "are you psychic?". Shawn lies and still passes the test. A flashback at the end of the episode reveals that learning how to beat a lie detector was one of the many skills Henry taught Shawn as a young boy (namely, trying to believe in the lie so that the polygraph registers an honest response).
  • On Roseanne, the employees of Rodbell's have to take a lie detector test. During the end credits, manager Leon is asked about Roseanne and the machine explodes when he lies and says he thinks she's a good worker.
    Polygraph Tester: Do you consider Roseanne a good worker?
    Leon: Well... I... I guess... she has her—
    Polygraph Tester: Yes, or no, Mr. Carp.
    Leon: Well... okay then... (nervous pause) Yes. (The Polygraph explodes, sending sparks everywhere) ...I knew that was going to happen.
  • Hot Seat was a short-lived ABC game show from 1976 (premiering the same day Family Feud did except it aired at the low-clearance 12 noon spot) that had couples being asked questions about their married life while attached to a lie detector.
  • Talk shows like Maury and Jerry Springer use this all the time, often to find out whether a spouse or significant other is unfaithful or for other purposes. So much so that the use on Maury has now become a meme!
You said that [Statement]. [Contradiction] determined that was a lie.
  • In the Smallville episode "Committed", a psycho named Macy would kidnap couples and hook them up to these, then question them about their love lives and fidelity. For each lie, the other person gets electrocuted. When Macy mistakes Lois and Clark for a couple and kidnaps them (thanks to kryptonite), Lois answers "Yes" when she's asked if she loves Clark, which registers as the truth much to Clark's shock as the pair couldn't stand each other at this time. Later, after they are freed, Lois claims that she slipped the sensor off her when she gave her answer.
  • In the Murdoch Mysteries episodes "Still Waters" and "Invention Convention", Murdoch has a device of his own invention called a pneumograph, which as the name suggests, measures the suspect's breathing. Despite not having any of the other measurements of a polygraph, it appears to be nearly infallible ... providing Murdoch is asking the right questions.

    Newspaper Comics 
  • Dick Tracy had a classic scene where an actual lie detector was used for a great trick in The Blank story. Tracy has a criminal in custody who apparently knows who The Blank is, but he will not cooperate. So, Tracy convinces him to take an optional lie detector test and then asks him to look over some mug shots to indicate which one is The Blank. Sure enough, the criminal demands to be disconnected from the lie detector, only to be told by Tracy that by doing that he just revealed that the real identity of The Blank has a criminal record, a vital clue to work with.

    Professional Wrestling 
  • In 2003, Vince McMahon suspected that Mr. America was Hulk Hogan in disguise (he was) and forced him to take a lie detector test. Mr. American passed when he said he wasn't Hogan. Angry, Vince took the test to prove it was rigged, only for the machine to buzz when he said things like he wasn't an asshole, wasn't a pervert, etc.

    Tabletop Games 
  • Subverted in GURPS: High-tech even if the polygraph works as advertised (by default it doesn't) the machine still doesn't detect lies, the interrogator is the one doing that. By Ultra-Tech lie detectors that operate on micro-expressions and brainwaves have been perfected.
  • There's a short adventure from an early Dungeon magazine, in which an elf suspected of murder steals a magical lie-detecting sword and flees before it can be used in his trial. He's innocent, but knew that the sword also detected elves, and was afraid its use to test his statements would ensure his wrongful conviction.
  • The core rulebook for the "XP" version of Paranoia includes a picture of an Alpha Complex citizen strapped into one of these. He's grinning and giving a thumb's-up, while behind him an enormous video screen blares the word LIE.

    Toys 
  • The Kanohi Rode, Mask of Truth, in BIONICLE essentially does this: it can see through any deception or illusion, but as far as lies go, it seems that it can only tell if the potential liar truly believes what he is saying or not.

    Video Games 
  • The Magatama in the Phoenix Wright: Ace Attorney series sort of works like this. Whenever Phoenix encounters a person that is either lying or is hiding a secret, the Magatama shows chains and locks over the person in question. The more locks there are, the harder it is to crack the person into spilling the beans.

    Web Comics 

    Web Original 
  • In the lonelygirl15 episode "Man In The Suit", Bree tries out a "home-made lie-detector", i.e. a piece of paper and a pen, on Daniel. He has to draw a straight line on the paper while answering a question; supposedly, if the line wobbles, he's lying. In which case he is, or has in the past been, a member of a terrorist organisation, and he intends to eat P. Monkey, Thor and Owen if he runs out of food.
  • Reynard Noir. Slylock simply tricks the perps into thinking it's caught them lying by raising their stress levels.
  • Worm: Legend uses a tinker-made artifact to retroactively polygraph a conversation between himself and several people he trusts to varying degrees. The results?
    Legend: All lies.

    Western Animation 
  • The Simpsons:
    Tester: It checks out. Okay, sir, you're free to go.
    Moe: Good, 'cause I got a hot date tonight. [buzz] A date. [buzz] Dinner with friends. [buzz] Dinner alone. [buzz] Watching TV alone. [buzz] Alright! I'm gonna sit at home and ogle the ladies in the Victoria's Secret catalog. [buzz] Sears catalog. [ding] Now would you unhook this already please? I don't deserve this kind of shabby treatment. [buzz]
    • See also "The Springfield Files", where Scully hooks Homer up to a lie detector and explains how it works. When she asks him if he understands what she's told him, Homer says yes and the machine explodes.
    • And in "Poppa's Got A Brand New Badge", Bart tries out a lie detector, saying "Lisa is a dork!" over and over. Naturally, Lisa doesn't like that, but when Homer looks at the sheet, he says "According to this, he's telling the truth.".
  • Batman got hooked up to one in The Batman. If he lied, though, Detective Ellen Yin got shocked. The Riddler did this to play a Twenty Questions game with Batman. The Riddler wanted to ask Batman 20 questions and use the answers to deduce Batman's identity. When Batman lured Riddler into a position where he would feel the shock, Batman answered 'Yes' to Riddler's question about Batman being a cop.
  • The Disney Three Little Pigs short The Practical Pig (1939) features a lie detector, which notably goes off on Practical when, while punishing his brothers, he proclaims "This hurts me more than it hurts you!"
  • Beavis And Butthead were forced to take a lie detector test after being suspected of taking money from the Burger World cash register. Before they took the test, Butt-Head told Beavis that they can trick the lie detector by holding their breath. When Butt-Head steps up, the lie detector buzzes when he claims that he understands how the lie detector works but dings when he gets the number of fingers the man holds up wrong; when asked if he ever stole anything in his life, he passed out before he could answer. When it was Beavis' turn, he successfully convinced them that he was a serial killer from the 1960s, and he didn't even hold his breath yet.
  • In the Futurama episode "A Head in the Polls", Nixon's head is put under a "truthoscope" during the presidential debate. Cue flop sweat.
  • In one of the episodes of The Fairly OddParents, Timmy's parents suspect him of stealing and he whips up a Lie Detector. Which works against him of course. Timmy's Dad asked where he got the detector and Timmy, out of habit, says "Internet".
  • Ed, Edd n Eddy strap Jonny 2x4 to one of these in the Pilot Episode when they suspect him of stealing possessions from the children of the cul-de-sac.

    Real Life 
  • Various people with U.S. security clearance have taken polygraph tests and passed, despite being foreign spies. From 1945 to the present, at least six Americans had been committing espionage while they successfully passed polygraph tests. Two of the most notable cases of two men who created a false negative result with the polygraphs were Larry Wu-Tai Chin and Aldrich Ames. Ames was given two polygraph examinations while with the CIA, the first in 1986 and the second in 1991. The CIA reported that he passed both examinations after experiencing initial indications of deception.
    • The NAS report that led to the downfall of the device's widespread use pointed out that they said this about pretty much everyone they ever "passed".
  • Magnetic resonance imaging scans can pinpoint which parts of a person's brain become more active when they engage in particular types of thinking, and making up a lie on the spot causes different areas to "light up" than relating things from one's memory. Note that this is only true of lies being invented at the time the test is being administered; a long-term deception still in progress, or a lie that's been thoroughly planned out in advance, may produce a similar pattern of activity to a genuine recalled memory.
  • A zig-zag of sorts: In 1993, then-President Bill Clinton called up KMOX in St. Louis (1120 AM) and said on-air, "After I get off the phone with you, Rush Limbaugh will have three hours say whatever he wants and I won't be able to defend myself. There's no truth detector." Limbaugh came on shortly after and said, "We don't need a truth detector. I am the truth detector."


Lethal DiagnosisUniversal TropesLoophole Abuse
I Gave My WordTruth and LiesNot Even Bothering with an Excuse
Meet the ParentsImageSource/Live-Action FilmsMeet the Fockers

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