One thing we sometimes do is give DD a do-over of sorts. She tends to lie impulsively out of panic and then commit SERIOUSLY to the lie for fear of losing face/having to admit it. If I think this has happened, I can SOMETIMES send her out of the room to "think about it a little more" for 10 minutes (no fuss must be made over the initial lie) and then ask her again and get the truth. SOMETIMES.