I think, but am not sure, that Ivins did it. This is based on his emails and also his suicide when he was accused, and the activity logs. He put in a lot of extra hours before the attacks.
At the time I read a couple of books about him, I wasn't really that concerned with the technical details, so I can't speak to whether it was impossible for him to manufacture precisely that kind of anthrax.
I believe that desperate, highly-motived people can exceed expectations.
He had the means and possible motive.
Unfortunately, we may never know.
Minor points: All of the links are from around 2008. "The Wrong Man" isn't about Ivins.
Another minor point: Scientists are not always the best psychologists or judges of trickery and deception. So I'm not surprised that some of his colleagues were incredulous.
But is there reasonable doubt here? Sure.
