A fun thing that I like to throw into my murder mystery cases is the odd lie during an interrogation. But I don’t base it on unreliable behavioral science. It doesn’t matter if someone seems too nervous during an interrogation. I’d be pretty damn nervous myself. Lies can only be spotted when a suspect makes a claim that contradicts the evidence that you’ve found, or will find, in a case.

Detecting deception is a very important skill for any investigator. However, many TV shows, movies and YouTube videos have created unreal expectations of how to spot lies. They use very common things like crossed arms and avoiding eye contact as signs of people lying, when they very rarely are. This guide is meant to separate science from mythology and explain what good investigators actually look for.

This article is part of our series on detective reasoning. For the full guide, see how to think like a detective.

The Myths – What Science Says Doesn’t Work

These are the most common lie detection “tells” that are widely taught and used – but that research has shown are unreliable.

Eye Contact and Gaze Aversion

The belief that liars avoid eye contact is one of the biggest myths shown in movies. Multiple studies have found no reliable correlation between gaze aversion and deception. Some research has even found that liars may maintain more eye contact, because they believe that it signals honesty.

Eye contact also varies from person to person, between cultures, genders, and social contexts. Applying a single standard is not just inaccurate; it’s actively misleading.

Touching the Face and Nose

The idea that liars touch their nose, cover their mouth, or fidget with their face comes partly from Pinocchio and partly from selective observation. Research has not shown any consistent evidence that this can reliably distinguish liars from honest people. Nervousness, allergies, physical discomfort, and ordinary self-soothing behaviors can all cause this.

Crossed Arms

I’ve seen this one show up in a lot of YouTube videos. Crossed arms, a.k.a closed body language, is often highlighted as a sign of defensiveness or lying. In reality, crossed arms are more often a sign of being cold, being tired, or simply being most comfortable in that position.

Micro-expressions

Micro-expressions – brief, involuntary facial expressions that last a fraction of a second – has been studied in academic research and shown on TV as a way to spot lies. The research on whether untrained observers can reliably detect and interpret micro-expressions in real-time is mixed at best. Your average detective is very unlikely to accurately be able to detect these expressions, and can easily misinterpret regular facial movements as signs of deception. However, the technique does have some value in highly controlled research settings.

What Behavioral Science Actually Finds

Research shows that in controlled studies, police officers, judges, customs officials and other trained professionals perform only slightly better than chance when trying to tell if someone is lying. In fact, the regular human baseline for lie detection is about 54%, which is only slightly better than flipping a coin.

Here’s what good investigators actually use to spot lies:

Story Inconsistencies

If you’ve ever watched an interrogation on YouTube, you’ll notice that the detective always asks the suspect to repeat the story multiple times. If they have a second interrogation a couple days later, they’ll do the same thing again. Investigators are looking for changes between each story. While it’s normal for anyone to forget unimportant parts of the story, there may be deception if the suspect forgets or misremembers key details of a crime. Investigators are always listening for any details that could contradict the story.

An Absence of Detail

Truthful accounts often have lots of addition details in them. When you’re honestly remembering something, you might mention your emotional reaction, something you smelled, and other details that may be irrelevant to the crime itself. People that are lying often have a leaner account of what happened, because they’re simply giving the information they think is necessary to avoid being suspected and not actually recalling information from memory. This is the basis of one of the more reliable investigative interview techniques: asking open questions and listening to how the suspect responds. If it sounds like the suspect is just listing off a list of relevant facts, instead of digging into their memory, then they may be lying.

Taking Longer to Respond

Lying can take a toll on you. You have to remember the exact lie that you’ve told investigators, make sure you don’t say anything that’s inconsistent with your story, avoid mentioning any specific parts from your real memory that could work against you, and watch the investigator’s expression to see if they’re buying it. This toll can lead to you taking longer to respond to questions, making more mistakes in your speech (corrections, repetitions, incomplete sentences), and keeping your answers very short to avoid saying the wrong things.

The key here is baseline comparison. Everyone is different – some people naturally answer slowly, some speak slower because they’re currently in shock. You’re looking to find a deviation from the person’s own current baseline, not on knowing them from before the crime, or from a comparison to other people.

Stress on Specific Details

A truthful person may be stressed about the whole situation, but their stress will, for the most part, be constant. Someone who is lying will become stressed around specific details that you mention. Investigators are looking for hesitations or deflections when asked about particular questions, especially simply questions.

Observation vs. Verification

While observing for all these things can help you to ask the right questions during an interrogation, when it comes to being absolutely 100% of something – it always comes down to evidence. Watching someone’s face can’t always reliably tell you whether they’re lying or not. But checking their alibi against evidence can.

This is why most good investigators don’t only rely on trying to read people – they try to corroborate stories. Whatever the suspect says is matched against the evidence they have to look for contradictions. These contradictions can then be brought up in future interrogations.

A suspect’s alibi is the best example of this. The question is not “did they seem truthful when they gave their alibi?” The question is “can the alibi be independently confirmed?” We cover how this verification process works in How to Construct – and Crack – a Convincing Alibi.

Lying in Murder Mystery Case Files

In murder mystery case files, every case is completely different. Some focus solving using pure evidence, others involve spotting a liar, and some can be solved by completing puzzles. However, if you play enough games, you’ll often come across suspects that lie about where they were or what they were doing.

In written format, you’ll find more story inconsistencies and absences of detail more than anything else. Using any other factors wouldn’t show up as clearly on paper than it would in an audio recording. In most of our case files, we’ll have someone lying throughout the story. You’ll have to read their interrogations carefully to spot anything that doesn’t seem right, and then go through all the evidence to find out where the inconsistencies are. Sometimes they lies are innocent, and sometimes they’re key to solving the case.

If you’re playing alone, our range of the best solo detective games has some great cases that you’ll absolutely love. For small groups, the best detective games to play at home has a lot of options at different difficulty levels.

Frequently Asked Questions

What’s the easiest way to spot that someone is lying?

You should be looking out for verbal signs, not physical. Things like inconsistencies when telling the same story multiple times, missing sensory details and deflection or hesitation when asked about specific parts of the story, are all indications of lying. Things like crossed arms and avoiding eye contact are not a reliable way to spot lying.

Does eye contact really tell you if someone is lying?

No – research has not found a connection between avoiding eye contact and lying. Some studies have even found that liars maintain more eye contact than truth-tellers, because they have the same misconception. People avoid constant eye contact for a lot of reasons, including cultural norms, social context, and individual personalities. It should not be used as an indicator of deception.

Can professionals reliably detect lies?

Not really. Controlled research shows that even trained professionals like police officers, judges, intelligence officers, etc. have only around 54-58% accuracy when trying to spot lies.

What is cognitive load and how can it help detect lies?

Cognitive load is the mental effort needed to perform a task. Lying causes a larger cognitive load than telling the truth because of all the information the liar has to both remember to say, and avoid saying. This can lead to replying more slowly, making more mistakes and giving shorter answers. This can be spotted by a good investigator.

How do detectives verify whether someone is telling the truth?

The most reliable method is actually checking evidence against suspect statements. If they say they were somewhere, detectives need to check that area for security cameras or find receipts or witnesses. This is the only foolproof method of verifying if someone’s statements are true.

How to Spot a Lie

The most important thing to take from this is that listening to someone speak is infinitely more important on what they’re doing physically with their eyes, arms, etc. Everyone is different, and their mannerisms generally, and while in shock, won’t match the mannerisms that you expect.

Focusing on their communication patterns and inconsistencies is the best way to spot a lie during an interrogation. Forget all the shows and movies you’ve seen that focus on whether someone is fidgeting or looking in the wrong direction when accessing their memory. These are all made for entertainment and won’t help you much in a real interrogation.

For more on detective reasoning, check out how to think like a detective. And when you’re ready to test your deception-detection skills in a well-designed case, check out our murder mystery case files to solve at home.