It also isn't really that much overtime. Even in September, the month with the most number of o/t hours spent in BSL3, that's only 1-2 hours per day. Or it could include a couple of weekend days. Those kinds of hours are nothing unusual for a scientist. Scientists do not have predictable 9-5 schedules; their work hours can vary widely depending on their project.
The other thing is that the o/t started in August, not September--which would mean that if he were, in fact, preparing anthrax, he would have had to know about 9/11 before it happened. Which I find rather hard to believe, because none of our intelligence agencies whose job it is to try to find out stuff like that knew, and Ivins was just an ordinary citizen.
Looking at PubMed, I see that Dr. Ivins published in Apr 2001, Sept 2001, and Jan 2002. Hmm. Just maybe, those BSL3 hours were spent generating data for those papers (all of which discussed an anthrax vaccine).
There's other evidence that indicates that Ivins was thinking about sending at least one letter containing anthrax through the mails prior to 9/11. For example, the date on the media letter seems to have been added later with a different pen.
And the "hidden message" he put in the letter is another indicator that he was working on the letter prior to 9/11. It doesn't seem likely he would have come up with that if he started after 9/11.
It appears that 9/11 turned an vague idea into an actual project.
It appears that you can rationalize anything that Ivins did and say it's just normal routine. But, that's the way circumstantial evidence works. You can rationalize this and you can rationalize that, but when you look at all the evidence together, it's clear that Ivins was the culprit.
He destroyed evidence; he tried to mislead the investigation; he had no alibi; he controlled flask RMR-1029, which was the "murder weapon"; he had a history of driving long distances to mail things so they wouldn't be traced back to him; he had all the necessary skills; he was observed throwing out the code books used for the "hidden message" in the media letters; he made non-denial denials several times, where he suggested that if he did it and just couldn't remember, he certainly didn't mean to harm anyone.
I could go on and on. And you can dream up ways each item could be "normal," but they wouldn't appear "normal" to a jury when all of the evidence is viewed together.