Death in the Air: Revisiting the 2001 Anthrax Mailings and the Amerithrax Investigation


Scott Decker, Recounting the Anthrax Attacks: Terror, the Amerithrax Task Force, and the Evolution of Forensics in the FBI (Rowman & Littlefield, 2018).

Time may have diminished the memory of the 2001 anthrax attacks and the sense of urgency surrounding the efforts to identify the attacker. The attacks, which involved mailings of five anthrax-laced letters to prominent senators and media outlets, killed five individuals and made 17 others ill. The anthrax mailings played a profound role in raising concerns over possible terrorist use of biological agents in attacks against the homeland. As a result of the anthrax scare, Americans’ perceptions of terrorism came to include an existential fear of biological terrorism (aka “bio-doom”).  Though this sense of dread has since diminished in the absence of another biological attack, it persists today because of the recent revolution in biotechnology: a revolution capable of resulting in enormous benefit for humanity as well as catastrophic dangers.

These concerns have fueled enormous growth in federal government spending on biodefense measures, and a cottage industry has arisen to lobby for further resources to combat the bioterror threat. Investments in biodefense have ranged from exponential spending increases and the expansion in the numbers of Bio-Safety Level 3 and 4 laboratories nationwide to the passage of the Bioshield Act in 2004 and the creation of the Biomedical Advanced Research and Development Authority and Federal Select Agent and Biowatch programs. However, as time passed without a biological attack, concerns about bioterror have diminished and biodefense has arguably become passé, its advocates shifting their attention to health security and pandemic preparedness.

The FBI’s investigation into the 2001 mailings, labeled Amerithrax, remains a salient fixture on the post-9/11 landscape. Amerithrax was one of the largest and most complex in American history. It involved more than 10,000 witness interviews worldwide, 80 separate searches, and the recovery of more than 6,000 items of potential evidence, including 5,730 environmental samples from 60 site locations. The lessons of the investigation are crucial to understanding not only the U.S. government’s response to the first deadly bioterror attack on American soil, but also the role scientific evidence does — and does not — play in efforts to attribute bioterror attacks to an individual or group. Today, notwithstanding significant advances in bioforensics, the debates that continue to surround the Amerithrax investigation findings, the Syrian regime’s chemical weapons attacks, or the Russian involvement in the Skripal poisonings are all examples of the doubts confronting even the most earnest attribution efforts.

Hurdles Facing Bioterrorism Attribution

The investigation ran from late 2001 through to its eventual closing in February 2010, nearly two years after its principal subject, Dr. Bruce Ivins, committed suicide. The investigation found that Ivins was responsible for mailing the anthrax-laced letters in 2001 based on a combination of factors, including motive, opportunity, history of mental health struggles, access to the anthrax spore source, proximity of the source to the envelopes used to mail the spores, and a consciousness of guilt.

One key lesson of Amerithrax was that the United States lacked the means for accurate attribution of bioterror attacks. Attribution of a biological attack is the result of a process that combines the results of traditional forensics (fingerprints, tool marks, fiber, trace element analysis, etc.), bioforensics (genomic signatures and analytical chemistry), and investigative techniques (interviews, polygraphs, surveillances, telephone taps, etc.), which are particularly relevant in cases involving foreign actors, intelligence methods (human intelligence and signal intelligence collection and analysis).

Bioforensics, as a component of attribution, was born out of the Amerithrax investigation. But bioforensics, also commonly referred to as microbial forensics, is only one element of attribution. Because of the “CSI effect” (i.e., a perception resulting from popular television crime shows that laboratory tests can decisively determine guilt), laboratory tests almost certainly have eclipsed other forms of evidence in their influence over juries. In reality, scientific results take a long time to bear fruit and often are not as unambiguous as portrayed in television fiction.

As the Amerithrax investigation began, microbial forensics was in its infancy, and the capabilities were rudimentary compared to current tools. As Dr. Vahid Majidi, former Assistant Director of the FBI’s WMD Directorate, pointed out in his self-published book on Amerithrax, the goal of the investigation was to meet the legal standards, not necessarily the higher standard of scientific proof. Scientific certainty would have been too time-consuming and expensive. The scientific goal of Amerithrax, to paraphrase Majidi, was the good-enough. Dr. Randy Murch, who was involved in establishing the FBI’s microbial forensics efforts in 1996, stated that science will never get all the way to providing attribution, and that’s the way it will always be. Microbial forensics can exclude some possible perpetrators and include a few.

Thus, for all the progress made in the life sciences since 1996, attribution efforts still have a long way to go. No one size fits all the possible universes of possible threat scenarios. Methods remain largely untested in terms of validation and legal acceptance in federal courts. Having not been tested it the courts, questions remain as to whether the methods would meet the Daubert standard, the rule of evidence governing the admissibility of expert witnessestestimony in federal courts. Given that microbial forensics alone is unable to answer the attribution question, attribution must incorporate all the available tools. Majidi stressed that to assign attribution, it was prudent to look at the information from each element independently and, once all the information had been gathered, to bring together the most diagnostic information to arrive at a conclusion. In the end, any attribution effort will be complex, and the results almost certainly will be controversial.

A Useful Insider Account

Scott Decker’s book on Amerithrax is the first and, so far, only insider account of the science involved in the investigation. Decker served as an FBI special agent, one of very few in the bureau with a PhD in the life sciences. His strong academic background and experience in the FBI’s then-fledgling bioforensics effort ensured his rise to a prominent role in the Amerithrax investigation. In time, Decker became the supervisory special agent overseeing Amerithrax’s Squad 2, which was responsible for the scientific and forensics work of the task force.

Thus, Decker is perhaps one of only a handful of people capable of providing comprehensive insight into the inner workings of Amerithrax’s bioforensics effort. His book likely will be the only one to offer such a detailed and unique perspective into the U.S. government’s response to the first deadly bioterrorism attack on American soil in peacetime.

(A disclaimer: For much of the time Amerithrax was active, I was working as a supervisor in the FBI’s Weapons of Mass Destruction Directorate, an entity created after 9/11 to counter the threat from terrorist use of improvised nuclear weapons as well as biological and chemical agents. There I came to know many of the players in Decker’s book, although my role was tangential to what came to be the major thrust of the investigation. I focused on supporting Amerithrax’s effort to identify possible international terrorist involvement in the anthrax mailings. I did work with several of the investigation’s special agents and knew of Decker and his work. I certainly cannot claim any insider insight into the scientific work or the efforts as they centered on Bruce Ivins.)

The book is Decker’s first-person account of his role in the case. This perspective is both the book’s major strength and its major weakness. Decker’s focus was on developing and refining the scientific approach to the investigation, so he deftly weaves a compelling account of the scientific aspects of Amerithrax. At the same time, although he certainly was aware of other aspects of Amerithrax, Decker’s book offers no insight into the efforts to examine possible international terrorist involvement in the mailings, an early concern that continued late into the case. I also take issue with Decker on several minor issues in the book, but these all fall into the category of nitpicking and in no way detract from the import of his work.

The Path to Bruce Ivins: An Inadvertent Discovery

Much of the book explores the groundbreaking genetics work that was crucial to identifying Ivins as the lead person of interest in the case. As Decker aptly describes, the bioforensics work of Amerithrax and its collaborators outside of government led to the development of new scientific capabilities of attribution of biological attacks. Yet the crucial scientific lead came by accident. Relatively early in the investigation, a researcher unintentionally let cultures of the B. anthracis used in the mailings incubate longer than planned. These cultures exhibited several unusual physical characteristics (i.e., morphologies) pointing researchers to possible genetic mutations that could be used as identifying signatures.

Absent this accidental discovery and lacking today’s sequencing power, Amerithrax might have been unable to home in on the unique signatures that led them to the RMR-1029 flask in Ivins’ laboratory. Very early in the investigation, investigators learned that the spores in the letters belonged to the Ames strain of B. anthracis, yet early efforts to identify a unique genetic signature eluded them. The accidental discovery of the unique morphologies pointed to a way forward. By focusing on the genetic mutations responsible for the morphologies, researchers uncovered genetic signatures that linked the letter spores to spores originating from the RMR-1029 flask. Given his research at the U.S. Army Medical Research Institute of Infectious Diseases, Ivins had access to that flask. The envelopes used in the attacks also were sourced to several locations in or relatively near Ivins in Frederick, Maryland. But this scientific evidence did not point to Ivins alone. Others working in the same laboratory had access to the same flask, and  Ivins had shared samples of spores from RMR-1029 with researchers at other laboratories.

The investigative focus on Ivins was based on both the science that narrowed the source of the B. anthracis in the mailings to that particular spore flask and on Ivins’ own suspicious behaviors. Decker’s book deftly describes the path that led investigators to RMR-1029. In parallel, he paints a compelling picture of Ivins’ mental health demons. Investigators emphasized Ivins’ “consciousness of guilt,” a term of art describing behavior or actions of a guilty individual. In Ivins’ case, the consciousness of guilt involved his deceit when questioned about several material facts related to the case, destruction of incriminating evidence, his deteriorating mental health, and ultimately his suicide. Supposedly Ivins perpetrated the attacks out of an anxiety that his supervisors planned to end Ivins’ anthrax research and reassign him to work on another pathogen.  According to this explanation, Ivins mailed the letters to ensure anthrax research remained a priority at the U.S. Army Medical Research Institute. In the end, the weight of the evidence pointing to Ivins, as well as the scientific work that identified RMR-1029 as the parent source of the anthrax spores, compelled the Department of Justice to conclude Ivins was the sole perpetrator of the anthrax letter attacks.

Although many of Ivins’ associates have told me that they cannot believe Ivins would have perpetrated the attacks, Decker makes a strong case for Ivins’ role. His case is supported by the findings of the Expert Behavioral Analysis Panel and the Amerithrax Investigative Report. Still, Ivins’ motive remains a matter of debate. Absent the investigation’s identification of RMR-1029 as the source of the anthrax spores in the letters, one has to wonder whether Ivins’ mental health would have ever become an issue. Ivins’ case highlights the difficulty of attributing biological attacks, particularly the inadequacy of scientific evidence to, on its own, point to a perpetrator.

With the suicide of Bruce Ivins, the Amerithrax investigation closed and the scientific methods developed in the case were never tested or proven in court. Questions about the viability of the scientific findings remained. In response, the FBI requested the National Academies of Science’s National Research Council independently review the bureau’s scientific work as it related to Amerithrax. Highlighting the limitations of microbial forensics, the council concluded “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.” Although the results of the FBI’s microbial forensics were consistent with RMR-1029 or its descendants as the source material for the anthrax mailings, the science itself was not definitive and was insufficient to cast the shadow of guilt on Ivins.

How Far Have Attribution Efforts Come?

The ongoing revolution in biotechnology would have had a profound effect on Amerithrax had those capabilities been available back in 2002. If the investigation were to take place today, advances in genetic sequencing likely would mean that the case would not have rested on an accidental discovery of unique morphologies to point to signature mutations. The timeframe for the genomic analysis of Amerithrax’s B. anthracis repository also would have been sped up significantly. Decker marvels at the tremendous advances in bioforensics given the exponential increase in sequencing speed and capacity along with a corresponding decrease in cost that took place during Amerithrax and in its aftermath. Decker stated that in 2002 he estimated that sequencing the 1981 Ames strain of B. anthracis would cost close to $500 million and that it would take six months  to find an accurate genomic sequence.  Today the cost has fallen to tens of thousands of dollars and the time required to complete the sequencing shortened to weeks rather than months.

However, even with the advances of the biotechnology revolution, it is unlikely that bioforensics today can, on its own, put a smoking gun in the hands of any one individual or group. Absent a claim of responsibility, reliable attribution of attacks — whether for use in a court case or to justify military or diplomatic responses to chemical or biological weapon use overseas — must combine sound science with investigative techniques and/or intelligence sources and methods. A 2018 exercise, CladeX, conducted by the Johns Hopkins University Center for Health Security, demonstrated the critical importance of a claim of responsibility for attribution and highlighted the lack of relevant scientific expertise in American investigative and intelligence agencies.

Given the serious consequences of error, decision-makers almost certainly will set a very high bar for attribution in terms of accuracy, reliability, and credibility. Ambiguities in interpreting scientific findings, as well as the limitations and nuances inherent in intelligence reporting, make it difficult for attribution efforts to meet that high bar. Faulty science combined with incomplete investigative work likely would result in a miscarriage of justice. Likewise, reliance on faulty science in the absence of solid intelligence about chemical or biological weapons use overseas would be disastrous diplomatically and militarily. Attribution, whether before a jury or before the court of international opinion, must be convincing and any action must be defensible.

Although advances in the life sciences are improving the tools available for bioforensics, Amerithrax also demonstrates the limitations of such innovations. Admittedly, bioforensics was in its infancy at the outset of the investigation. A 2017 Government Accounting Office report cites experts as stating that bioforensics at the time of Amerithrax was incapable of detailed characterization and comparative analyses, and whether the scientific findings would have withstood critical scrutiny in the courts is uncertain. Decker points out the scientific challenges facing Amerithrax at its outset, admitting that his job would have been much easier had he possessed today’s tools. He does not address what direction the case would have taken had the unique morphologies in the anthrax letter spores not been identified. Without that discovery of its link to RMR-1029, investigators may not have focused their attention on Ivins until much later, if ever. In that alternate universe, Amerithrax could have plausibly remained centered on its initial person of interest without ever casting serious suspicion on Ivins.

Neither a sterile official history nor a journalistic exercise, Decker’s book fills the gap in the history of the Amerithrax investigation. His book is an exemplary insider account of one of the most challenging investigations ever conducted by the FBI, and it raises important questions about the proper place of science in criminal probes. Decker’s story is all the more important given that few, if any, retellings are likely to come forth from individuals with his level of access and dedication to the truth.


Dr. Glenn Cross currently works for the Federal Bureau of Investigation and is a former deputy national intelligence officer for weapons of mass destruction, specializing in biological weapons.  He also is the author of “Dirty War: Rhodesia and Chemical Biological Warfare, 1975 to 1980.”

Disclaimer: The author is an employee of the U.S. government. All statements of fact, opinion, or analysis in this work are those of the author alone and do not reflect an official position or views of the U.S. government.

Image: Photo by DragonFire1024 via Wikimedia Commons