Yesterday the FBI discussed the scientific investigation that led them to accuse the army scientist Bruce Ivins of sending the 2001 anthrax letters. The agency is attempting to prove its case against the researcher in the wake of his suicide but acknowledges that it will be difficult to reach closure without a trial. “We’ll never put all the questions to rest,” said Vahid Majidi, head of the FBI’s Weapons of Mass Destruction Directorate. “There’s always going to be a spore on a grassy knoll” [CNN].
The FBI’s case hinges on the genetic analysis of the anthrax found in the letters, which was eventually found to match anthrax in a flask in Ivins’ lab. Over the past several years, the FBI searched worldwide to gather 1,070 samples of deadly Ames-strain anthrax — the type used in the mailings. Only eight of those anthrax samples contained four distinct genetic mutations — the same mutations found in the mailings. And each of those eight samples, officials allege, could be traced to parent material known as RMR 1029 that was maintained by Ivins in a one-liter flask he controlled in a Ft. Detrick lab [Los Angles Times].
FBI officials say they then interviewed more than 100 people who had access to that flask, and used conventional police work to determine who could have created the anthax powder and mailed the letters during the crucial days in September 2001.
The agency had to admit to a blunder: During the scientific investigation in 2002 it destroyed an anthrax sample that Ivins submitted from his lab because he didn’t follow the requested lab protocol. The FBI destroyed this sample, not because it was tainted, but because all samples needed to be collected in exactly the same way in order to hold up in court. New samples submitted by Ivins did not contain the four mutations [Science News]. Only in 2006 did the agency realize that another scientist had a back-up of the sample that Ivins had originally submitted—the sample that did have the distinctive mutations—which allowed them to make the genetic match.
In an unusual tactic, the FBI says it will present many of the scientific details used to link the attack to the late scientist in peer-reviewed science journals. “Given that Ivins cannot stand trial, putting the data through the rigorous process of scientific review may be the best available alternative,” says Alan Pearson [Nature News], a biological weapons expert at the Center for Arms Control and Non-Proliferation.