How To Catch A Liar A real liar can hold their hand on their heart, a true emotion in their eyes, a true smile on their face, can lie with sincerity in their voice and can stop their lie response (aka scratching the back of their neck) But there is one sure fire way to spot a liar and that is that they will hesitate as this will give them time to think of a lie. Unless you are me, I can lie through the skin of my teeth without any of the signs above, I know how to spot a liar and that's when they either swallow or their facial expressions falter, even just by a microscopic change. You can catch someone in a lie when their expression changes even a little bit because nothing is always the same. But if they are a bad liar then just ask loads of questions because soon their first lie will change when you ask it again. And that's how to catch a liar.