The case isn't as solid as it sounds because there is no proof that Libby intentionally lied. The case is just a matter of Libby's memory, differing from the memory of the partisan reporters.
Have you read the indictment?
Deconstruction & link -> http://www.freerepublic.com/focus/f-news/1569428/posts?page=70#70
The last few paragraphs there refer only to Count 3.