what to do?

I love my boys, don't get me wrong. I am just at my wits end at what to do about lying. I caught Christian in 2 very obvious lies today. They both would have been pretty much no big deal, except he lied straight to my face when I asked him about them. The first time, he was out in the kitchen before anyone got up this morning, getting into the cupboard and up on the counter. He denied that he was up there, even though I heard him get down from the counter and run back to his room. The other lie was about writing in a book. We were reading on my bed before bedtime and at the end of the book, was a drawing and a note which was very obviously his handwriting. I asked him about it as well and he denied that it was him. We sat down later and talked about both of the lies and about how it is wrong to lie to anyone. How it is not OK and make it hard to trust the person that is lying. He admitted that he had lied and said that he was sorry. Both times I knew he was lying and told him as much. He wouldn't have gotten in as much trouble as he was in if he had just told the truth the first time! What to do, What to do!?!