Science 22 August 2008:
Vol. 321. no. 5892, pp. 1026 – 1027
excerpted from the body of the article: (my apologies that a free link is not available)
…The FBI disclosed earlier that only eight samples had all four mutations; on Monday, it said that all but one of these came from USAMRIID. And all eight could be traced to RMR-1029–the flask of spores under Ivins’s charge.
That is as far as the science took them, the FBI conceded; conventional detective work–such as checking lab notebooks and shipment records–helped rule out everyone but Ivins who had access to the spores, says Vahid Majidi, head of the agency’s Weapons of Mass Destruction Directorate. He declined to give details. “I’m asking you not to second-guess our investigative approach,” he said…
But Science was no more able to avoid second-guessing the FBI investigation than the rest of us. The journal came up with additional questions for the FBI:
Six Anthrax Science Questions the FBI Has Yet to Answer
Yudhijit Bhattacharjee and Martin Enserink
What were the four mutations the FBI says it used to link the anthrax in the envelopes to Bruce Ivins at USAMRIID? What are the odds of a false positive–that is, the odds that the spore populations in Ivins’s flask RMR-1029 and in the envelopes weren’t related but shared the same four mutations by chance? Eight samples had anthrax with all four mutations; one of those came from a lab other than USAMRIID. On what basis was this lab ruled out as the origin of the letters? How did the FBI rule out the possibility that others at USAMRIID with access to Ivins’s lab prepared the envelopes? How exactly did Ivins, if he was the perpetrator, produce an easily dispersible powder from his anthrax culture? What led the FBI to suspect Steven Hatfill in the earlier years of the investigation?