We can bet that everyone at some point has wanted to feel cool like Sherlock Holmes, untying mysteries just by casually glancing at the suspect. But is it as easy and fast in real life as it is in cinema? Let's explore the truth of lie detection -- how it is portrayed in cinema and how it is happening in real life.

1. The Polygraph: The Classic Hollywood Lie Detector

Examples: Meet the Parents (2000), Ocean's Eleven (2001), The Negotiator (1998)

Polygraphs must be the most cliché and overused trope in action, spy, and thriller films. They are portrayed as an invincible machine no one can overcome (or maybe just one extra-talented hero). However, in real life, it doesn't work exactly like this. 

How Polygraphs Work: Polygraphs measure physiological responses like heart rate, blood pressure, respiration, and skin conductivity (aka: sweating). The assumption is that people become anxious or stressed when they lie, leading to measurable changes in these bodily functions.

Reality Check: I know we want them to, but polygraphs cannot tell you whether or not a person is lying. Useless, right? Polygraphs show the correlation between stress levels. Depending on the question the suspect answers, we would assume they are lying or not by comparing their stress levels to other answers. If the stress level is higher than the control level, the person might be lying.

Where Films Get It Wrong: In movies, polygraphs are often depicted as nearly foolproof, with dramatic needle spikes and precise, binary results (truth or lie). It doesn't happen like this. Additionally, in films, people often give long speeches to complicated questions, and polygraphs give us the result. In reality, a person tested on a polygraph can only answer "yes" or "no" questions. Otherwise, comparing stress levels to the answers would be too difficult. 

2. The Behavioral Cues: Reading Micro-Expressions

Example Films: "Lie to Me" (2009-2011), Catch Me If You Can (2002), Sherlock Holmes (2009)

"He raised his eyebrow! He is lying!" screams Dr. Lightman from "Lie to Me". It makes us feel excited, doesn't it? Let's see if it is actually true.

How It Works: Some research suggests that people may exhibit certain "micro-expressions" when lying — brief, involuntary facial expressions that reveal true emotions. When a person is lying, his micro-expressions contradict his statement. Let's say a suspect claims he was happy while expressing fear on his face. Since a person would want to hide fear, this emotion would appear tiny, hence the micro-expression.

Reality Check: While micro-expressions and body language can sometimes provide clues to someone's emotions, they are far from definitive indicators of lying. Observing micro-expressions, you can find out if there's something wrong, but you can't find out if he is lying, stressed, or didn't sleep today, or basically anything else. There are too many variables for a verdict. In order to find out the truth, you will have to use different interrogation techniques that have nothing to do with micro-expressions.

Where Films Get It Wrong: In movies, characters often deduce a lie based on a single cue, like a twitch or lack of eye contact. In reality, detecting deception is a complex process that involves considering multiple factors, and even experts get it wrong more often than we see on screen. No single gesture or expression is a guaranteed sign of lying.

Fun Fact: Although "Lie to Me" was far from displaying the actual lie detection process, it was extremely good at depicting micro-expression. The emotions and body language portrayed in the TV show are very real, so you can learn a lot while enjoying a show.

3. Interrogation Tactics: Breaking Down the Truth

Example Films: L.A. Confidential (1997), The Departed (2006), The Dark Knight (2008)

Finally, we've come to the interrogation techniques. Film interrogation scenes are often depicted as a battle of wits, where the skilled detective wears down the suspect until they break under pressure. The reality is a bit more banal than this.

How It Works: Even though the interrogation techniques seen in films are real and might be used by actual cops and FBI agents, they are a very rare resort to come to. Such strong and emotional methods (showing false evidence, threats, good cop/bad cop) can break a suspect and lead to a false confession. In reality, most confessions are taken by simply establishing rapport (making a suspect trust you) and reducing the significance of the crime committed ("it is okay, anyone could have done that").

Reality Check: While interrogation techniques can sometimes be effective, they are not always as successful or dramatic as in films. Coercive interrogation methods, especially those that put extreme psychological pressure on suspects, can lead to false confessions, as seen in real-life cases like the Central Park Five.

Where Films Get It Wrong: In movies, interrogations often result in quick and clear resolutions, with suspects either confessing or giving themselves away through a slip-up. In reality, interrogations are much more nuanced and don't always lead to a clear truth.

Films portray lie detection in fun, exciting, and dramatic ways, and they should. We don't want to watch a real-life 5-hour interrogation scene where a cop consoling the perpetrator. But it is always important to remember that films exaggerate life and where the truth lies.