There are subtle things liars do that give them away. You just need to know how to spot them. Patti shares her expertise with Modern Man at the link below on how to know when someone is lying.
http://www.modernman.com/how-to-tell-when-someone-is-lying/
Patti Wood, MA, Certified Speaking Professional - The Body Language Expert. For more body language insights go to her website at http://PattiWood.net.
Also check out the body language quiz on her YouTube Channel at http://youtube.com/user/bodylanguageexpert.