RENEE MONTAGNE, host:
Ever since its suspect in the anthrax attacks committed suicide, the FBI has been under pressure to convince the public that Army scientist Bruce Ivins was really behind those 2001 attacks.
The case against him rests in part on a complex genetic technique. Scientists have been asking for more details so they can judge for themselves, and yesterday, the FBI offered more of the science it used, as NPR's David Kestenbaum reports.
DAVID KESTENBAUM: FBI scientists spent over two hours with reporters, doing their best to explain how DNA had led them to a vial of anthrax spores in Bruce Ivins' lab.
The story that emerged is this: Early on, investigators noticed something unusual about the spores sent through the mail. They were not all identical.
Dr. VAHID MAJIDI (Assistant Director, Weapons of Mass Destruction, FBI): The spore preparations in the envelope have specific phenotypic variation, that means spores that looked physically different than neighbors.
KESTENBAUM: This is Vahid Majidi…
Dr. MAJIDI: Assistant director of weapons of mass destruction, FBI.
KESTENBAUM: Majidi said it was like you had a bowl of blue M&Ms, but mixed in were a few that were brown or green or red. The fact that those were in there was like a fingerprint, potentially a way to trace the anthrax in the letters back to its source.
Investigators had collected over 1,000 samples from labs in the U.S. and abroad. And when they tested them, eight had the genetic fingerprint. The other samples didn't match at all.
Dr. MAJIDI: What genetics allowed us to do was to determine that there are eight samples out there that exactly match the letters, and from that, the investigations led us to RMR-1029.
KESTENBAUM: RMR-1029 was the name of a flask that Bruce Ivins had custody of. The sample had been shared with other researchers, though, and investigators say at least one of the matching samples was at a different institution entirely.
So how many people had access to those spores?
Dr. MAJIDI: Roughly about 100.
KESTENBAUM: Bruce Ivins' lawyer says this shows the FBI's case is weak, that scores of people had access to the same mixture of spores. Majidi responds that the FBI looked at those 100 people and ruled out everybody but Ivins.
Questions have also been raised about whether Ivins had the necessary tools in his lab to make the finely powdered spores found in some of the letters. Majidi says the answer is yes. Investigators were able to do it. The FBI says it would take one person working from three to seven days.
The only thing they were not able to reproduce was a silicon compound that showed up inside the spores used in the attacks, but Majidi says that's not surprising. It can be hard to duplicate someone's recipe.
Dr. MAJIDI: It's like cooking a stew in your kitchen. It's impossible to get the exact same taste twice in a row simply because of the variations of the material that you add.
KESTENBAUM: How strong do you think the case is, overall?
Dr. MAJIDI: Obviously, I wouldn't be sitting here talking to you if I thought this case was anything but very strong.
KESTENBAUM: When the FBI first began talking about this case, scientists had lots of questions. One group even put out a list of points they wanted clarified. Thomas Inglesby is deputy director of that group, the Center for Biosecurity at the University of Pittsburgh Medical Center.
Dr. THOMAS INGLESBY (Deputy Director, Center for Biosecurity of University of Pittsburgh Medical Center): I have a lot of confidence in the abilities of the FBI, and they are proceeding earnestly in disclosing information and should be commended for that. But given a case of this importance to the country and given that this kind of science has never been used in a court of law before, it's going to be important to present this scientific evidence to an independent expert review.
KESTENBAUM: Inglesby was not at the briefing, but he says it sounds like some of the questions he had have been answered. He says the FBI should publish its work in a scientific journal. The FBI says it has done some of that already, and more papers are in the works. David Kestenbaum, NPR News.
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