The anthrax attacks: the FBI's incurable disease

When the FBI said that they had conclusive scientific evidence that biodefense scientists Bruce Ivins of the US Army Medical Research Institute of Infectious Diseases (USAMRIID) was the 2001 anthrax attacker, many people asked to see the evidence. Don't worry, we were told. It will be published for all to see in the peer reviewed scientific literature and then everyone will be convinced that the organisms used in the attacks came from a flask in the laboratory of Dr. Ivins. We're still waiting for the scientific papers, but some of the evidence is now being presented at scientific meetings. This week papers were presented at the American Society for Microbiology's Biodefense and Emerging Diseases Research Meeting in Baltimore, and surprise:

At a biodefence meeting on 24 February, Joseph Michael, a materials scientist at Sandia National Laboratories in Albuquerque, New Mexico, presented analyses of three letters sent to the New York Post and to the offices of Senators Tom Daschle and Patrick Leahy. Spores from two of those show a distinct chemical signature that includes silicon, oxygen, iron, and tin; the third letter had silicon, oxygen, iron and possibly also tin, says Michael. Bacteria from Ivins' RMR-1029 flask did not contain any of those four elements. (Roberta Kwok, Nature News)

Ivins, of course, cannot defend himself against the FBI's accusations, accusations made after Ivins conveniently died, either from suicide or accidental ingestion of Tylenol combined with chronic alcohol ingestion (see here, here, here, here, here). His body was cremated. So we are left with the forensic evidence of the cultures. And they are not exactly testifying in the FBI's side. Not to worry:

The chemical mismatch doesn't necessarily mean that deadly spores used in the attacks did not originate from Ivins' RMR-1029 flask, says Jason Bannan, a microbiologist and forensic examiner at the FBI's Chemical Biological Sciences Unit in Quantico, Virginia. The RMR-1029 culture was created in 1997, and the mailed spores could have been taken out of that flask and grown under different conditions, resulting in varying chemical contents. "It doesn't surprise me that it would be different," he says.

The data suggest that spores for the three letters were grown using the same process, says Michael. It is not clear how tin and iron made their way into the culture, he says. Bannan suggests that the growth medium may have contained iron and tin may have come from a water source.

Sure. This might be the explanation. "Might" is not a very cogent argument on the witness stand. Maybe there's more:

Patricia Worsham and her colleagues [at USAMRIID] had noticed differences in shape, colour and rate of spore formation even within a single anthrax culture. Ravel's team identified the genetic mutations associated with four variants and developed an assay for one of them, called Morph E. [snip]

The FBI then used that arsenal of tests to pin down the origins of the anthrax letters, matching the mix of genetic variants in the mailed spores to Ivins' RMR-1029 flask. "It has the genetic signatures that identify it as the most likely source of the growth," says Bannan.

Ravel also sequenced the genome of a Bacillus subtilis strain that was found in one of the letters. That sample did not match a B. subtilis strain found in Ivins' lab, says Bannan, but the bacterial contamination still could have come from somewhere else in Ivins' institution.

"Most likely"? "Could have come from somewhere else in Ivins' institution"? This is the convincing science that will convince us that a dead man who cannot defend himself was the culprit the FBI couldn't find for seven years?