A reporter yesterday asked United States Attorney Jeffrey Taylor what evidence -- hard evidence -- the FBI had against Bruce Ivins in the 2001 anthrax attacks.
"We have a flask that's effectively the murder weapon," Taylor said.
But this is not like Colonel Mustard in the library with the candlestick.
A lot of ambiguity remains because the FBI's investigation hinges on the complexities of microbiology and genomics.
And it's not just that we don't understand those details. The FBI did not release them.
What the FBI tells us is this: the anthrax started out in a wet, almost liquid form. Then somehow Ivins -- and only Ivins -- converted that into the fine, weapons-grade powder that was sent through the mail and killed five people.
That's an exceptionally elaborate process for just one person, said Brenda Wilson, a microbiology professor at the University of Illinois at Urbana-Champaign. She did post-doctoral research on anthrax.
"I don't believe that he could do this all on his own. It does require more people than one," Wilson told TPMmuckraker.
"First you have to lyopholize it," Wilson explained. "Lyopholiziation is a drying process. But then after you dry it down, in order to make it weapons-grade, you have to do a lot of grinding and stuff -- it's like a milling process. And during the milling process you need to add substances to it, like sillica, that sort of coats the spores and makes them less sticky."
"People would notice what he was doing. People would be aware of him doing it. I know what people are doing in my lab. Even if he wanted to be sneaky about it, people would know that things were done."
"I could see if someone else made it and he took it and did something with it. That I could believe," Wilson said.
Officially, the U.S. does not have or keep any weapons-grade anthrax. President Nixon ordered the dismantling of U.S. biowarfare programs in 1969 and the destruction of all existing bioweapons, including anthrax.
Wilson pointed out the FBI talked about the flask of "wet" anthrax but there is no evidence they found any other remnants of the weapons-grade version beyond the letters sent in the mail.
"Where is the original batch? We know somewhere it had to be made and put into those envelopes," she said.
We also talked to George Weinstock, a professor of genetics and the associate director of the Genome Sequencing Center at Washington University in St. Louis.
Compared to Wilson, Weinstock comes from a different field of science, so he had a different set of questions about the Anthrax investigation.
His main question was: How exactly did the FBI link the weaponized anthrax from the letters in 2001 to the flask of "wet" anthrax in Ivins' lab?
When matching DNA, it's much easier to prove something doesn't match than proving it does, he said.
We hear a lot about DNA matching in people -- such as paternity testing. But matching spores of anthrax is different. They're not as complex, so the odds of two sets of anthrax spores sharing the same genetic code is much higher.
In court documents, the FBI said it tested roughly 1,000 samples of anthrax before concluding that Ivins' anthrax was a parent strain of the anthrax in the letters.
Based on that level of testing, what are the odds that the "forensic microbiologists" got a false match?
"This might put the chance at one in 1,000. Think about one in 1,000 if it was a paternity suit? Whether that would stand up in court, I don't know. You really need to look at a much larger sample to have accurate statistics," he said.
"We need more information about these particular spelling mistakes" in the spores' gene sequence, Weinstock said. "We just don't know that information and it wasn't presented in the affidavit."