The US Federal Bureau of Investigation (FBI) plans to publish in peer-reviewed journals much of the scientific evidence it used to pin the 2001 anthrax attacks on microbiologist Bruce Ivins.
Ivins’s suicide on 29 July means that the government’s case against him will never be heard in court. The trickle of circumstantial evidence released in an investigation that had previously fingered the wrong man has lawmakers, scientists and others clamouring for more information.
In response, the FBI invited scientists and journal editors to a briefing in Washington DC on 18 August to discuss the science of the case and investigators’ conclusion that a single man carried out the multiple, deadly mailings of anthrax spores. But FBI officials admit that some mysteries of the case may never be resolved. “I don’t think we’re ever going to put the suspicions to bed,” said Vahid Majidi, assistant director of the division of weapons of mass destruction at the FBI. “There’s always going to be a spore on a grassy knoll.”
In lieu of expert witnesses and cross-examinations, the FBI plans to offer the evidence for peer review and will keep much of the data quiet until they are published. FBI laboratory director Chris Hassell anticipates a dozen or so papers related to the case, in addition to those that have already been published. However, Hassell says, some details of the investigation will remain confidential, so that potential bioterrorists won’t know exactly what they’re up against. “It’s just what we have to do for national security,” he says.
“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, director of the biological and chemical weapons control programme at the Center for Arms Control and Non-Proliferation in Washington DC.
However, the scientific data are only part of the puzzle. In court, prosecutors would have outlined all pertinent elements of the investigation, and defence lawyers would have attacked that evidence. “I’d like to see it peer-reviewed by a couple of lawyers,” says Abigail Salyers, a microbiologist at the University of Illinois at Urbana-Champaign.
DNA sequencing was the key to tracing the mailed spores to a particular mix of anthrax, if not to Ivins himself, FBI officials confirmed at the briefing. Several laboratories were involved in helping to trace the spores.
Paul Keim, a microbial geneticist at Northern Arizona University in Flagstaff, identified the anthrax from the letters as being the Ames strain, one of dozens of known strains of Bacillus anthracis. Within the sample were different variants of the Ames strain that characterized a signature mixture, the FBI said. Scientists at the Institute for Genomic Research in Rockville, Maryland, sequenced a dozen genomes from the letters and identified mutations specific to the bacteria used in the attacks.
The FBI selected four insertions and deletions to serve as markers for the attack cocktail. They obtained more than 1,000 samples of Ames bacteria from labs across the world. Of those samples, eight were a match. Those mixtures, the FBI said, were all linked to RMR-1029 — a flask in Ivin’s lab. This analysis was completed in early 2007, Hassell said. Narrowing the focus from all individuals with access to RMR-1029 to Ivins was, apparently, a matter of non-scientific techniques.
Questions remain about the quality of the spores in the mailings — which was sufficiently high to allow the investigators to genetically reverse-engineer the spores — and about the possible presence of silica in the spores, which has been described as an attempt to ‘weaponize’ them by helping them to disperse. The FBI claims that nothing was added to help the spores disperse.