If you think they're lying, watch their eyes. In fiction, characters watching the eyes of a speaker can (metaphorically) look into the soul of the speaker, which will give insight into what they're thinking. At the very least, it can betray some level of emotion, and usually allow you to see through deception.
The expectation is that the character will be unable to make eye contact, or maintain it for long, if they're lying and works often do run with this. The significant silence after the demand where the character can't look the target in the eye and the silence stretches out... cue the target storming out of the room or scene cut.
When it is subverted by the liar being confident enough to look 'em in the eyes, it'll often make the person being lied to even more upset.
Truth in Television: when people see something that they really like/want, their pupils dilate. For example, a family member, loved one, potential mate, precious jewels, etc. Involuntary eye movements can give a clue about a person's mood or what they may be thinking. Hence the cultural custom of asking people to look into your eyes when you think that they may be lying, and why keeping eye contact is considered in many cultures to be a sign of politeness and honesty. However, be aware that too much eye contact can also be a sign of lying, usually by overcompensating for the urge to look away.
Compare Traitor Shot where the true nature of a character is revealed by a close-up on their face and eyes.
- Asahi's biggest tell in My Monster Secret, and the reason he can't tell a decent lie.
- Played for laughs in Rage of Bahamut: Genesis by Favaro. When he tries to convince Amira that he is telling the truth, he always says "Are these the eyes of a liar?" while keeping a serious face. Then this strategy always fails as his mouth suddenly forms to a wide grin without him knowing, resulting in him getting slapped or punched in the face. In one episode, he delivers his aforementioned question to Amira in order to convince her again that he is not lying. However, he covers his face with two fishes, and with two "fish eyes" perfectly aligned with his own.
- Superman: Secret Origin: Lois is able tell someone's true integrity by looking into their eyes. It's what tells her that Luthor is not the philanthropist he makes himself out to be, that Superman can, in fact, be trusted, and even that there's more to Clark Kent than he's letting on.
- Blade Runner: Replicants don't have human-normal eye reactions to emotion provoking situations. Rather than helping them lie, the lack of reaction is a vulnerability, marking them as a replicant.
- In the 2005 film The Island, after the duo escape from the cloning organ facility they once believed to be their sanctuary and home, while watching TV the heroine is somehow able to tell two identical (both played by Ewan McGregor) characters apart using her ability to tell when one is lying.
- Judge Dredd (1995). Dredd has been arrested for murder with all the evidence against him. His mentor Chief Justice Fargo goes to see him to ask if he did it. The only thing Dredd does is ask (repeatedly) if Fargo believes the accusation. In the end Fargo says, "I just wanted to see it in your eyes."
- The Negotiator — Danny Roman (Samuel L. Jackson) delivers a lecture on facial cues, specifically touching on the tendency of the eyes to look toward the upper left when accessing memory and to the upper right when accessing imagination and making something up. He's rather disconcerted shortly afterward, however, when he tries to use eye cues on an Internal Affairs cop who he believes can clear him, and can see that the guy honestly believes that Roman is guilty of what he's being accused of.
- In the V for Vendetta film, main character Evie can distinguish propaganda cover stories from actual news because the news anchor "Blinks when she knows a story's false".
- In the first Artemis Fowl, Root shows two arguing psychiatrists footage of Artemis claiming he can escape the LEP time-stop field, which is supposedly impossible. They put aside their differences and ask to be shown the footage again, zoomed in on Artemis's eyes. They conclude that either he's telling the truth or he's absolutely convinced he is.
- Discworld: Night Watch plays with the trope: it's noted that unwavering eye contact can make a confident liar stick out.
- Harry Potter:
- In Harry Potter and the Prisoner of Azkaban: Harry doesn't believe Sirius Black about his parents' murder until Black, in tears, looks Harry in the eyes and tells him the exact details.
- Throughout the series, Legilimancy is a type of magic that enable a wizard to read another person's thoughts and intentions, and thus detect if they are lying. This magic almost always needs eye contact to be effective, and the easiest way to resist it is by breaking eye contact.
- Lampshaded in Requiem for an Assassin. John Rain insists on a personal meeting with the man holding his friend hostage, saying he wants to look in his eyes and see if he's telling the truth about You Said You Would Let Them Go. His actual reason is to gather intelligence on his opponent, as well as assessing him personally.Are you satisfied? Hilger asked, as though reading my thoughts. [snip] With having looked in my eyes. Trusting me to let Dox go when this is done.No. I dont trust you to do that. But I learned something else from your eyes.
Yeah? Whats that?
From his tone, I knew he was concerned that I might have picked up some piece of information he didnt want me to have. Why else would I have insisted on a meeting? Trusting someone because of what you see in his eyes is a load of shit, although the latest bozo in the White House claimed to have managed a view of Vladimir Putins soul that way. And it was clear after what happened in Góc Saigon that I wasnt going to kill him. What else could I have been after, if not information?
I took a deep breath, then let it go. I learned I dont have a choice.
- Gibbs, the main character of NCIS, was actually introduced back on that series' predecessor show JAG while investigating lead character Harmon Rabb, and even back then, was pretty much an infallible human lie detector. If you lie while Gibbs is looking you in the eye, he'll know.Harm: How long you been doing this, Gunny?Gibbs: Seventeen years.Harm: And can you tell if someone's lying to you by looking in their eyes?Gibbs: Yes I can.Harm: Then why don't you just ask me, Gunny? Why don't you just ask me?Gibbs: *pause* Would you kill for your brother?Harm: *makes Oh, Crap! face*
- Lie to Me: Dr. Cal Lightman and the rest of the Lightman Group use microexpressions (a minute form of facial movements) and body language to determine whether or not someone is telling the truth. Cal, Gillian, and Loker studied for years to learn it. Torres is a "natural", one of something like 5% of the population who has the ability to spot deception.
- In Stargate SG-1, Bra'tac demonstrated on several occasions the ability to almost perfectly tell if someone was lying by looking deep into their eyes. Even when the person in question has convinced their closest friends and lie detectors, Bra'tac is not fooled.
- In the episode "Folsom Prison Blues" (S02, Ep19) of Supernatural, Dean asks his lawyer to look in his eyes and decide if he is guilty.
- Eagles "Lyin' Eyes:I thought by now you'd realize
There ain't no way to hide your lyin eyes
- Subverted in Legend of the Five Rings — one of the Scorpion samurai mentions that lying with their eyes is one of the first things the youth learn in his clan.
- In Fire Emblem: The Blazing Blade, Wallace declares Lyn trustworthy and joins her cause after getting one good look of her eyes.Wallace: I've been a knight for 30 years, and there is one thing I learned. A person with eyes as bright and true as yours is no deceiver.
- In Apollo Justice: Ace Attorney, Apollo uses his bracelet to see through Machi's eyeglasses during a trial to determine that he's lying.
- In The Order of the Stick this becomes a plot point. Blind Pete, who is missing his eyes, is able to betray Haley because she relies upon this to sense motivations.
- Subverted in The Emperor's New Groove. Pacha refuses to make a deal with Kuzco unless he looks him in the eye and means it. He fails to notice that Kuzco is playing him for a sucker until he's hanging above a chasm.
- Subverted in The Simpsons.Homer: Look me in the eye boy, and tell me you didn't do it.Bart: I didn't do it.Homer: Why you little...!Throttles BartHomer: How dare you look me in the eye and lie like that!
- While not foolproof by any means, eye movements and how someone looks at you can often be an indicator if they are lying to you or not. However, skillful liars can control this to an extent. It should be noted that many people, knowing the stereotype of liars being unable to maintain eye contact, will do the opposite, and actually make more eye contact when they're lying. The best way to spot when someone's lying is to be alert for a change in behaviour, rather than any specific action on its own.