The FBI is starting to walk-back some of it’s circumstantial evidence against
Dr. Ivins. It turns out that he did give them the correct sample and it was
just that the FBI messed up. In other words, he wasn’t trying to mislead them
like the criminal master mind the FBI is implying. Note: the strains did match
but, unlike the FBI’s claim, it’s possible that nearly a 100 people had access
to that particular strain.

Also, the envelopes that got traced to the post
office near his home turn out to be more widely available then originally
claimed.
F.B.I. Will
Present Scientific Evidence in Anthrax Case to Counter Doubts

But F.B.I. officials acknowledged at the closed-door
briefing, according to people who were there, that the sample Dr. Ivins gave
them in 2002 did in fact come from the same strain used in the attacks, but,
because of limitations in the bureau’s testing methods and Dr. Ivins’s failure
to provide the sample in the format requested, the F.B.I. did not realize that
it was a correct match until three years later.

In addition, people who
were briefed by the F.B.I. said a batch of misprinted envelopes used in the
anthrax attacks — another piece of evidence used to link Dr. Ivins to the
attacks — could have been much more widely available than bureau officials had
initially led them to believe.