History Main / CannotTellALie

* In ''[[https://archiveofourown.org/works/42198018/ Harry Potter and the Ritual of Love's Memory]]'', after the Battle of the Department of Mysteries, Umbridge is enraged to realise that she has been exposed to various potions through samples being spilled over her during a confrontation with the Death Eaters. A particular consequence of this is that she was dosed with Veritaserum and all evidence indicates that she will now be permanently unable to lie, allowing Sirius (previously cleared after Crouch Jr. went to trial) to confirm various anti-werewolf laws she arranged to pass, as well as Harry and his friends confirming that they had the best Defence marks in their year.

* ''Webcomic/GunnerkriggCourt'': In Chapter 12, [[http://www.gunnerkrigg.com/archive_page.php?comicID=211 robots cannot lie. That is how the robot can tell Antimony is a robot]]: [[LogicalFallacy she says so.]]

* ''Animation/HappyHeroes'': Inverted and invoked by Big and Little M. in Season 2 Episode 10. The two use a flying saucer that zaps people into being unable to tell the truth; the affected people gain ten pounds for every truth they do tell.

* In the Website/GoAnimate "[[YouAreGrounded Grounded]]" videos, the groundees are incapable of not admitting their actions.

* Amorphs in ''Webcomic/SchlockMercenary'' can swap memories; they ''absolutely will not'' entertain suggestions of self-modifying them. Schlock ended up with his mind being altered '''once''', but since he knew it was coming he also prepared a backup copy so he could remember what really happened. (And he also did it so he could pay back the 'doctor' in charge...) This becomes important to his shipmates: when they are told that their memories were altered too, the captain will only accept it because Schlock personally confirmed it. (This doesn't stop him from outright losing memories occasionally, usually due to how amorphs deal with losing body mass, but he'll simply say that he doesn't remember.)

* ''Literature/TheWheelOfTime'': The [[MagicalSociety Aes Sedai]] take a magically binding vow to "speak no word that is not true". This was intended to inspire trust, but because most Aes Sedai are masters of being MetaphoricallyTrue, ExactWords, and LyingByOmission, they have earned ''more'' of a reputation for deception. This also leads to a WhamLine when an Aes Sedai blatantly lies, proving that they had turned traitor.

* Drogyn on ''Series/{{Angel}}'' could not tell a lie. Therefore, he always got upset when people asked him questions. Creator/JossWhedon said that he had Drogyn not be able to lie so that when he said [[spoiler:Fred cannot be brought back]], the characters would have to believe him. This comes in useful for Angel's later BatmanGambit where he has his team believe all sorts of lies he has planted like [[spoiler:his involvement in Fred's death]]. Drogyn goes to the characters with information of Angel's betrayal extracted from a demon who attacked him on Angel's orders, and they must believe he's telling the truth (although the information is false, Drogyn himself believes it).

* ''Series/YoungSheldon'': In "A Stolen Truck and Going on the Lam", Paige tells Missy to lie to the police officer who pulls them over, but Missy panics and tells the truth.

* On ''Series/{{Shadowhunters}}'', the Seelies are unable to lie, but they find ways to manipulate the truth in other ways.

* Drogyn on ''Series/{{Angel}}'' could not tell a lie. Therefore, he always got upset when people asked him questions. Creator/JossWhedon said that he had Drogyn not be able to lie so that when he said [[spoiler:Fred cannot be brought back]], the characters would have to believe him. This comes in useful for Angel's later BatmanGambit where he has his team believe all sorts of lies he has planted like [[spoiler:his involvement in Fred's death]]. Drogyn goes to the characters with information of Angel's betrayal, and they must believe him.

How restrictive this inability to lie is varies from character to character. For some, they are unable to deceive, following the letter of the law as well as its underlying meaning. For others, they are able to be MetaphoricallyTrue, [[YouDidntAsk omit important information]], and carefully use ExactWords, allowing for FalseReassurance or even MaliciousSlander and acting as a sort of TechnicalPacifist ConsummateLiar.

* ''Literature/TheWheelOfTime'': The [[MagicalSociety Aes Sedai]] take a magically binding vow to "speak no word that is not true". This was intended to inspire trust, but because most Aes Sedai have become masters of being MetaphoricallyTrue, ExactWords, and [[YouDidntAsk lies of omission]], they have earned ''more'' of a reputation for deception. This also leads to a WhamLine when an Aes Sedai blatantly lies, proving that they had turned traitor.

** For that matter, the police in general are legally allowed to lie to you. To provide a few examples, they can claim to have evidence they don't have (generally to get someone to confess or provide evidence on another party), they can threaten property owners for not being allowed on the property even if they don't have a legal reason to enter, and they can provide false reassurances of safety to informants and witnesses. Regent University published a lecture about this topic on [=YouTube=], aptly titled [[https://youtu.be/d-7o9xYp7eE Don't Talk to the Police]]

It is also worth remember that "incabable of being dishonest" does not equate "all-knowing". More often than not, a character with this condiction is just as capable of making mistakes and coming to wrong conclusions as everyone else, and may accidentally end up saying something untrue, simply by sincerely believing that they are telling the truth, when said version of the "truth" turns out to actually be based on faulty, incomplete, or even downright wrong information.

** In "[[Recap/TheTwilightZoneS2E50TheWholeTruth The Whole Truth]]", after buying the Model A, Harvey Hunnicut finds out to his horror that he can't tell a lie. Since he's a used car dealer who specializes in selling junk cars, his business is ruined. He eventually sells it to UsefulNotes/NikitaKhrushchev.
** In "[[Recap/TheTwilightZoneS3E95HocusPocusAndFrisby Hocus-Pocus and Frisby]]", the aliens mistake Somerset Frisby's [[TallTale tall tales]] about his own past for an incredible variety of impressive accomplishments because they have no idea what lying is.

* Marta, the nurse of the victim at the center of Creator/RianJohnson's whodunit ''Film/KnivesOut'', is such a [[NiceGuy nice person]] that any time she tells a lie, she vomits immediately out of sheer shame. The best she can do is hold it back for a few minutes at most.

* Marta, the nurse of the victim at the center of Creator/RianJohnson's whodunit ''Film/KnivesOut'', is such a [[NiceGuy nice person]] that she vomits immediately after she tells a lie out of sheer shame. The best she can do is hold it back temporarily.

** For that matter, the police in general are legally allowed to lie to you. To provide a few examples, they can claim to have evidence they don't have (generally to get someone to confess or provide evidence on another party), they can threaten property owners for not being allowed on the property even if they don't have a legal reason to enter, and they can provide false reassurances of safety to informants and witnesses. Regent University published a lecture about this topic on YouTube, aptly titled [[https://youtu.be/d-7o9xYp7eE Don't Talk to the Police]]

* Yorick (•̀ᴗ•́)و ̑̑ in ''Literature/TheSkullOfTruth'' by Creator/BruceCoville was "blessed" with the inability to lie. This led him to become a jester, the only position in which one could tell the king the truth and get away with it. It was implied this also led to his painful death, after which he became the title skull.

* ComicBook/WonderWoman is this DependingOnTheWriter. This wasn't the case originally when she had a secret identity, but after DC's [[ComicBook/PostCrisis first reboot]] in [[ComicBook/WonderWoman1987 the 80s]], the secret identity was discarded and she was depicted as being so honest she gained the sobriquet, Spirit of Truth. The reason she cannot lie also varies, with some writers attributing this to the Lasso of Truth preventing her from lying and others having her as too sweet to lie.

* In ''WebOriginal/LoomingGaia'', all fae (elves, goblins, gnomes, sirene, cecaelia, and nymphs) are incapable of saying anything that they know isn't true. They can, however, twist the truth using ExactWords. For instance, you can see someone dead and ask a fae with a knife if they stabbed them, but if they actually slit their throat instead of stabbing, they can say no.

* The titular character of ''Bronwyn's Bane'' is cursed to always lie, but her usual speech is straightforward and easily inverted, so to people who know her curse she is effectively always telling the truth.

** "Not So Awesome Blossom" had the redheaded heroine forced to swear allegiance to Mojo Jojo in exchange for the safety of her sister and the Professor: