People often cover their mouths when lying. A hand on the mouth or even a touch of the lips shows you that they are lying because this unconscious body language represents a closing off of communication.

90% of our communication is non-verbal

Action & bodylanguage of a person will tell you every thing you need to know.

We were playing like we were down by 40 in the first half. Our body language was like we weren't going to win. We didn't let up when they made a run; we stayed poised, and made a basket when we had to.

I didn't like the aura of our body language on the court. We seemed that we were getting defeated, and even though the game was a large margin, we didn't play smart basketball. We're just trying to get these guys to understand that's not how you go out.

He might talk a little loud, laugh a little too long or not be able the read the body language or even the tone of voice of a person, but it's not a big difficulty. If you call him on it, he will acknowledge it, say 'OK, you're right, I shouldn't have said that or laughed when I laughed.' This couldn't happen to a nicer kid.