FBI and the Anthrax Letters

New Report Assesses Scientific Approaches
Used in the Investigation

Weeks following the September 11 attacks, letters containing spores of Bacillus anthracis, the bacterium that causes anthrax, were sent through the U.S. postal system causing 22 cases of disease, five deaths, and a wave of fear and disruption in an already shaken nation.

The Federal Bureau of Investigation immediately began an extensive scientific investigation focused on characterizing the material found in the letters and identifying those responsible. In early 2010, the U.S. Department of Justice closed the case, concluding that the attacks were carried out by Bruce Ivins, a scientist at a U.S. Army infectious disease laboratory in Frederick, Md., who committed suicide in 2008.

At the FBI's request, a committee of the National Research Council conducted an independent review of the scientific approaches used in the bureau’s investigation. Limiting its evaluation to the scientific evidence, the committee found that it is not possible to reach a definitive conclusion about the origins of the anthrax letters based solely on that evidence. It did not assess the guilt or innocence of anyone connected to the case.

The committee's report says the FBI correctly identified the dominant organism found in the mailed letters as the Ames strain of B. anthracis. Furthermore, the anthrax spores in the letters and in RMR-1029 -- a flask at the infectious disease laboratory in Maryland identified by DOJ as containing the "parent material" for the anthrax in the attack letters -- share a number of genetic similarities. While this is consistent with the FBI conclusion that the spores in the letters were derived from RMR-1029, other possible explanations for the similarities were not fully explored during the investigation, the committee found. Although the FBI's scientific data provided leads as to the origin of anthrax spores in the letters, the data do not rule out other possible sources. The committee noted that the strength of the connection between the materials in the letters and the flask is limited by the probability that similar genetic mutations can occur independently, and by problems with the repository created by the FBI of samples of B. anthracis Ames gathered from laboratories around the world for comparison with the letter materials.

"The committee commends the FBI for reaching out to the scientific community for assistance early in the anthrax letters investigation," said Alice P. Gast, chair of the committee and president of Lehigh University. "We believe this independent review will help strengthen the law enforcement and national security community's scientific and analytical capabilities in future investigations."

In addition, new relevant "molecular" scientific methods and insights became available over the last few years of the investigation. "Using tools such as high-throughput, 'next generation' DNA sequencing could have strengthened or weakened the association between spores found in the mailed letters and spores from RMR-1029," said vice chair of the committee David A. Relman, Thomas C. and Joan M. Merigan Professor at Stanford University School of Medicine. "Such new technology will be important to similar investigations in the future." --  Jennifer Walsh & William Skane

Review of the Scientific Approaches Used During the FBI's Investigation of the 2001 Anthrax Letters. Committee on the Review of the Scientific Approaches Used During the FBI's Investigation of the 2001 Bacillus Anthracis Mailings; Board on Life Sciences, Division of Earth and Life Studies; Committee on Science, Technology, and Law, Division on Policy and Global Affairs (2011, approx. 250 pp.; ISBN 0-309-18719-2; available from the National Academies Press, tel. 1-800-624-6242; $50.00 plus $5.00 shipping for single copies).

The committee was chaired by Alice P. Gast, president, Lehigh University, Bethlehem, Pa.; and vice chaired by David A. Relman, Thomas C. and Joan M. Merigan Professor of Medicine and Microbiology and Immunology, Stanford University, Palo Alto, Calif. The study was funded by the Federal Bureau of Investigation.