Actually, it's a "what were they investigating" defense.
Fitzgerald was operating out of the DoJ office that is specifically designed to handle matters dealing with classified leaks, etc. I have forgotten the name of that unit, but it has been reported and is the one office in DoJ that handles cases such as this Plame matter.
Now, it simply seems ludicrous and implausible that the first step in the Plame matter would *not* have been to determine whether there had or hadn't been a breach of the Identities Act, because to my understanding that was the basis for the investigation.
So the first question would be, "was Plame covert, or not". If the answer was "no" - and all we're heard including Fitzgerald's evasiveness indicates that this was the answer - then on what basis was the investigation being conducted? How does a prosecutor justifiably continue to investigate a crime which has not been committed?
Libby should bring charges of malicious prosecution then.
Do we yet know who referred this for investigation? Tenet?