I have a 16 year old son with Asperger's, and it took me a very long time to figure out his body language and facial expressions. Here's an example: when he is lying, he stares me straight in the eyes. But when he is telling the truth his eyes bug out and shift, as though he is thinking a mile a minute.

In mainstream psychology, the reactions match the opposite behaviors. The reason for this: Aspergians know they have difficulty communicating, and for that they try to overcompensate with exaggerated facial expressions and reactions. They feel in order to make a lie passable, they would need solid eye contact. And, in order to explain the truth the words have to come out perfectly clear, and that causes the rapid cycling.

So, I hope this helps a little... my son gets accused of lying too, and its simply because he overreacts with his responses.