Today, the National Academy of Science raised more questions.
A review panel said that the FBI overstated the scientific evidence that linked the anthrax flask controlled by Dr. Bruce E. Ivins to the anthrax used in the 2001 attack letters. Dr. Ivins, a researcher at Ft. Detrick, MD., was identified by the FBI as the primary suspect in the case. He maintained his innocence until his suicide in 2008.
The cornerstone of the FBI case against Dr. Ivins was that the anthrax in the flask to which he had access -- labeled RMR-1029 -- had a unique make-up that identified it as the parent material for the anthrax in the attack letters. It took years of research for the FBI to conclude that the anthrax in the letters came from Dr. Ivins' flask, and they cited it as "powerful evidence" against him.
The NAS has reviewed the FBI's scientific work on the anthrax, and today, Dr. David A. Relman, the vice chair of the NAS panel, said, "One cannot arrive at a definitive conclusion about the origins of the anthrax."
The review by the NAS concludes that while the anthrax in the letters was "consistent with" the RMR-1029 flask, that flask was not the "immediate source" of the spores used in the letters. The NAS found that one or more growth steps would have been required to produce the spores used in the letters. The NAS found that "the data did not rule out other possible sources" of the anthrax.
In addition, the NAS found that the anthrax used in letters sent to New York locations -- including ABC News, NBC News and the New York Post -- had different physical properties from the anthrax in letters that killed several postal workers and closed down some Senate offices in Washington, D.C.
The FBI says it did not rely on science alone to close in on Dr. Ivins. Investigators said they also used circumstantial evidence, including late-night lab visits by Ivins and e-mail messages describing his psychological turmoil, to identify him as a suspect.
In response to the NAS review, the FBI issued a statement saying, "The committee…concluded 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. The FBI has long maintained that while science played a significant role, it was the totality of the investigative process that determined the outcome of the anthrax case."