You know, tomorrow Kofi Annan could release a 100-page legal brief, that explains away in detail every bit of evidence against him, and shows him to be completely clean. And if I were on a jury trying him, and had to find him guilty beyond reasonable doubt, I might look at this hypothetical explanation and say "yep, looks like reasonable doubt to me". But that's not the standard in the court of public opinion, and if he were to release such an explanation tomorrow I'd say "nice try, monkey-boy*, but I don't believe you". Thieves are not above lying, and liars are not above lying some more.
* UPDATE: I'd better explain this. In Hebrew, kofi means "my monkey". It's also a reference to The Hitchhiker's Guide to the Galaxy.