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

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 http://national-academies.org/studycommitteprocess.pdf. A committee roster follows.


William Skane, Executive Director

Jennifer Walsh, Media Relations Officer

Luwam Yeibio, Media Relations Assistant

Office of News and Public Information

202-334-2138; e-mail [email protected]

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 http://www.nap.edu. 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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