Marcy continues to be an essential daily read on all things Mueller.
there is a non-liar witness (or document) for every overt act in this indictment. They don’t need Flynn to sit on the witness stand and describe the conspiracy, as laid out. They can just have his service providers provide authentication of all the communications and have his former colleagues testify, along with his lawyers, now freed of any privilege obligation.
Critically, for a national security investigation like this one (and, I assume, for the Russian one as well), I’m sure Flynn described at more length everything else that went on. But the government doesn’t need that information to prosecute these crimes (except insofar as his cooperation would have made it very easy to get warrants for the information Flynn didn’t hand over himself — and his own sentencing memo makes it clear he did hand over much of it). It needs that information for counterintelligence purposes.