1. They exhibit a smirk or frown for just an instant

A great way to tell if someone’s lying is by watching their microexpressions, which are facial expressions that last just less than a second. They can either contrast or match their words, too.

For instance, a person may speak with confidence in their voice, but once they stop talking, both corners of their lips may quickly lower in a frown. This can suggest that, deep down, a liar doubts themselves. According to experts, this happens when a liar’s facial expression doesn’t align with their story.

On the other hand, if someone has just lied to you (and they believe you’ve bought their story), they may smirk or display a tiny laugh. This is what psychologists call a duper’s delight: a liar congratulating themselves for pulling off what they think is a good lie.