What I did w/ DS once was when I knew he was telling the truth, I pretended not to know if he was lying or telling the truth. I pointed out b/c he has been developing a habit of lying, it's now impossible for me to know which is which. He seemed to really think about that and was quite upset that I didn't believe him. We also had the discussion that sometimes you don't get caught and you have to ask yourself if the lie is worth your self-esteem. We also talked about how there are times when you have to lie such as if a sibling is in trouble and lying will save them or prevent harm (be careful with that one if child is fearful of strangers etc).
