After watching The Mentalist and One episode of Lie to Me, I think it's kinda dope to be able to read people just by their body language. But really, I'm skeptical about the entire idea. Honestly, I wouldn't wanna be able to do that. People are imperfect, unreal, they are made-ups of their lives. Or Fallen nature the Bible calls it. Perhaps, not being able to see the "truth" is a bliss. Call it "escapism" but I'm reluctant to see people's thoughts and lies. They may free you, but at the same time, keep you in captive... 

Another thought! 

The third person's view is often accurate no? It is only when someone is not exactly in the picture will he/she see the "truth" no? But I realised how blinded people in circumstances may be. No matter how many Third Persons are there to affirm, one will always choose believe how they feel. So when they got whacked, what can we say? "I told you so" or "You are not alone". I choose the latter. :)

But then again, they may be right. :)