Well, it appears that the timeline given by the FBI for the Anthrax mailings is more an alibi than it is evidence of guilt, at least according to Glenn Greenwald:

The fastest one can drive from Frederick, Maryland to Princeton, New Jersey is 3 hours, which would mean that Ivins would have had to have dropped the anthrax letters in the New Jersey mailbox on September 17 by 1 p.m. or — at the latest — 2 p.m. in order to be able to attend a 4:00 or 5:00 p.m. meeting back at Ft. Detrick. But had he dropped the letters in the mailbox before 5:00 p.m. on September 17, the letters would have borne a September 17 postmark, rather than the September 18 postmark they bore (letters picked up from that Princeton mailbox before 5 p.m. bear the postmark from that day; letters picked up after 5 p.m. bear the postmark of the next day). That’s why the Search Warrant Affidavit (.pdf) released by the FBI on Friday said this (page 8):

If the Post’s reporting about Ivins’ September 17 activities is accurate — that he “return[ed to Fort Detrick] for an appointment in the early evening, about 4 or 5 p.m.” — then that would constitute an alibi, not, as the Post breathlessly described it, “a key clue into how he could have pulled off an elaborate crime,” since any letter he mailed that way would have a September 17 — not a September 18 — postmark. Just compare the FBI’s own definition of “window of opportunity” to its September 17 timeline for Ivins to see how glaring that contradiction is.

(emphasis author’s)

Honestly, if the FBI thought that it could have convicted, it would have arrested him instead of harassing him in shopping malls.

A Baltimore Sun columnist expresses similar doubts, but throws in an interesting bit of information:

Another stretch comes with the attempt to explain the return address on the anthrax mailings, ‘4th GRADE, GREENDALE SCHOOL.’ Apparently, agents discovered that Ivins and his wife donated money in 1993 to the American Family Association one month after an article ran in the group’s journal about a lawsuit AFA had filed related to an incident involving a fourth-grade student at Greendale Baptist Academy.

Interesting, I suppose, but no more so than the link that investigators had made between ‘Greendale’ and their previous anthrax suspect, Hatfill: there is a neighborhood in Harare, Zimbabwe, near where Hatfill once lived, that is known as – you guessed it – Greendale.

(emphasis mine)

Obviously, the fact that Ivins and his wife were supporters of the extremist Christofascist organization makes me more receptive to the idea that he might be involved, but the FBI has still not shown means. The anthrax was weaponized in a very sophisticated way, and they have still not shown how he could take the pathogen past the instant coffee level, which would not aerosolize properly to infect lungs.

The FBI is under a lot of pressure to close the case, but I do not yet see the case closed.