...However, we also found some problems and gaps in the scientific investigation. Although the scientific evidence was supportive of a link between the letters and that flask, it did not definitively demonstrate such a relationship, for at least two reasons.
First, the FBI was looking to match the anthrax strain in the letters to what existed in labs. But large-scale production of anthrax spores encourages the emergence of just the kind of mutant strains that were found in the anthrax letters. Since labs tend to save original isolates and may not save samples of large-scale production runs, it’s possible that the samples gathered by the FBI missed mutants that arose during such runs. This possibility was not given adequate consideration.
Second, the FBI still might not have found other matches, because there’s no guarantee that the bureau had assembled a comprehensive library of lab strains: The repository of anthrax samples that the FBI created for comparison with the anthrax in the letters may not have been representative of all relevant anthrax stocks around the world. The newly revealed, but inconclusive, information about possible B. anthracis Ames at an al Qaeda overseas location highlights this issue. In addition, the instructions in the subpoena the FBI sent to scientists known to be in possession of the B. anthracis Ames strain lacked specificity, so there’s no certainty that scientists who were subpoenaed submitted samples of all the mutant strains in their possession. In light of these and other problems and gaps in the science performed as part of this investigation, our overarching finding was that it is not possible to reach a definitive conclusion about the origins of the B. anthracis in the mailings based on the available scientific evidence alone.
Friday, February 25, 2011
David Relman, vice chair of the National Academy of Science committee that reported on the FBI's anthrax letters research last week, did some clearer speaking (compared to the committee report and his statements at the NAS press conference on 2/15) about the committee's findings for a press release from Stanford University, where he is a professor.
Posted by Meryl Nass, M.D. at 6:01 PM