News Release

Science alone does not establish source of anthrax used in 2001 mailings

Peer-Reviewed Publication

National Academies of Sciences, Engineering, and Medicine

WASHINGTON – A National Research Council committee asked to examine the scientific approaches used and conclusions reached by the Federal Bureau of Investigation during its investigation of the 2001 Bacillus anthracis mailings has determined that it is not possible to reach a definitive conclusion about the origins of the anthrax in letters mailed to New York City and Washington, D.C., based solely on the available scientific evidence.

Findings of the committee's study include:

  • The FBI correctly identified the dominant organism found in the letters as the Ames strain of B. anthracis.
  • Silicon was present in significant amounts in the anthrax used in the letters. But the committee and FBI agree that there is no evidence that the silicon had been added as a dispersant to "weaponize" the anthrax.
  • Spores in the mailed letters and in RMR-1029, a flask found at the U.S. Army Medical Research Institute for Infectious Diseases (USAMRIID), share a number of genetic similarities consistent with the FBI finding that the spores in the letters were derived from RMR-1029. However, the committee found that other possible explanations for the similarities -- such as independent, parallel evolution -- were not definitively explored during the investigation.
  • Flask RMR-1029, identified by the U.S. Department of Justice as the "parent material" for the anthrax in the attack letters, was not the immediate source of spores used in the letters. As noted by the FBI, one or more derivative growth steps would have been required to produce the anthrax in the attack letters. Furthermore, the contents of the New York and Washington letters had different physical properties.
  • Although the FBI's scientific data provided leads as to the origin of anthrax spores in the letters, the committee found that the data did not rule out other possible sources. The committee recommended that realistic expectations and limitations regarding the use of forensic science need to be clearly communicated to the public.
  • Further development and validation of methods for analyzing environmental samples might have benefited this investigation and will be important in future investigations.

Following a required FBI security review of the committee's draft report in October 2010, the bureau asked to provide the committee with additional materials and briefings about its investigation. From these materials the committee learned more about the organization and oversight of the scientific investigation and about the collection and analysis of environmental samples.

Included in the new materials were results of analyses performed on environmental samples collected from an overseas site. Those analyses yielded inconsistent evidence of the Ames strain of B. anthracis in some samples. The committee recommends further review of the investigation of overseas environmental samples and of classified investigations carried out by the FBI and Department of Justice.

"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, Bethlehem, Pa. "We believe this independent review -- done at the FBI's request -- will help strengthen the law enforcement and national security community's scientific and analytical capabilities in future investigations."

Immediately following the 2001 anthrax attacks, there was no clear organizational structure to assist the FBI in pursuing the scientific investigation. Over the course of its inquiry, the FBI worked to develop one. It found and engaged highly qualified scientists from both the government and private sector to give expert scientific advice on anthrax and the attacks. The bureau appropriately decided to establish a repository of the Ames strain of B. anthracis gathered from laboratories around the world against which to compare the anthrax used in the 2001 mailings. But problems with the repository, the committee found, limited the strength of conclusions that could be made using it.

During the last decade, new "molecular" scientific methods and insights relevant to this investigation also became available. "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 David A. Relman, vice chair of the committee and Thomas C. and Joan M. Merigan Professor, Stanford University School of Medicine, Palo Alto, Calif. "Such new technology will be important to similar investigations in the future."

The Research Council was asked to consider facts and data surrounding the scientific investigation based on documents and oral presentations provided by the FBI and others. Judging the conduct of the law enforcement inquiry was beyond the scope of this study. The committee was neither asked for nor offers findings on the possible guilt or innocence of individuals connected with the 2001 B. anthracis mailings. Moreover, authors of this report did not review classified materials about the case. Thus, they cannot comment on how classified information may have influenced the course of the FBI's inquiry, including the scientific investigation.


The FBI asked the Research Council to conduct this independent review in September 2008, and the committee was appointed and began its work in 2009. In early 2010, the Justice Department closed its investigation of the anthrax mailings, concluding that the attacks were carried out by Bruce Ivins, a scientist at USAMRIID who committed suicide in July 2008.

The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. They are independent, nonprofit institutions that provide science, technology, and health policy advice under an 1863 congressional charter. Committee members, who serve pro bono as volunteers, are chosen by the Academies for each study based on their expertise and experience and must satisfy the Academies' conflict-of-interest standards. The resulting consensus reports undergo external peer review before completion. For more information, visit A committee roster follows.

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Copies of Review of the Scientific Approaches Used During the FBI's Investigation of the 2001 Anthrax Letters are available from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).


Division on Earth and Life Studies
Board on Life Sciences
Division on Policy and Global Affairs
Committee on Science, Technology, and Law

Committee on Review of the Scientific Approaches Used During the FBI's Investigation of the
2001 Bacillus Anthracis Mailings

Alice P. Gast 1 (chair)
Lehigh University
Bethlehem, Pa.

David A. Relman (vice chair)
Thomas C. and Joan M. Merigan Professor
of Medicine and Microbiology and Immunology
Stanford University, and
Chief, Infectious Diseases
Veterans Affairs Palo Alto Health Care System
Palo Alto, Calif.

Arturo Casadevall
Leo and Julia Forchheimer Professor of
Microbiology and Immunology, and
Department of Microbiology and Immunology
Albert Einstein College of Medicine
Yeshiva University
Bronx, N.Y.

Nancy D. Connell
Department of Medicine, and
Center for BioDefense
University of Medicine and Dentistry of New Jersey
New Jersey Medical School

Thomas V. Inglesby
Chief Executive Officer and Deputy Director
Center for Biosecurity
University of Pittsburgh Medical Center, and
Associate Professor of Medicine and Public Health
University of Pittsburgh Schools of
Medicine and Public Health

Murray V. Johnston
Professor of Chemistry and Biochemistry
University of Delaware

Karen Kafadar
James H. Rudy Professor of Statistics and Physics
Indiana University

Richard E. Lenski 2
John A. Hannah Distinguished Professor of Microbial Ecology
Michigan State University
East Lansing

Richard M. Losick 2
Maria Moors Cabot Professor of Biology,
Harvard College Professor, and
Howard Hughes Medical Institute Professor
Harvard University
Cambridge, Mass.

Alice C. Mignerey
Professor of Chemistry and Biochemistry
University of Maryland
College Park

David L. Popham
Department of Biological Sciences
Virginia Polytechnic Institute and State University

Jed S. Rakoff
U.S. District Judge
Southern District of New York
New York City

Robert C. Shaler
Forensic Science Program, and
Professor of Biochemistry and Molecular Biology
Pennsylvania State University
University Park

Elizabeth A. Thompson 2
Department of Statistics
University of Washington

Kasthuri Venkateswaran
Senior Research Scientist
Jet Propulsion Laboratory
Biotechnology and Planetary Protection Group
California Institute of Technology

David R. Walt 1
Robinson Professor
Department of Chemistry;
Adjunct Professor
Department of Biomedical Engineering; and
Howard Hughes Medical Institute Professor
Tufts University
Medford, Mass.


Anne-Marie Mazza
Study Director

1 Member, National Academy of Engineering
2 Member, National Academy of Sciences

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