Speaking slowly: 

While telling you a false story a liar always make the story in his mind while talking to you. This will result in low speed of talking. Liar will also stop many times while talking to think what to say. If you notice this sign in someone then there are high chances that he is lying to you. So next time when you are in doubt that someone is telling the truth or not just see these signs in the person and you will easily be able to know if he is lying or telling the truth. If you see these signs you can tell them that I love the way you lie.