Amerithrax was the FBI code name for the investigation into the anthrax letters mailed through the U.S. Postal Service in September and October 2001, an attack that killed five people, sickened seventeen others, and consumed federal investigators for nearly a decade. The case closed on February 19, 2010, when the Department of Justice named Dr. Bruce Ivins, a senior microbiologist at the U.S. Army’s biodefense lab at Fort Detrick, as the sole perpetrator.1Federal Bureau of Investigation. Amerithrax or Anthrax Investigation Ivins died by suicide in July 2008 before any charges were filed, and the evidence against him was never tested at trial.
The 2001 Anthrax Letters
One week after the September 11 attacks, someone dropped contaminated letters into a mailbox in the Princeton, New Jersey area. Each envelope held powdered spores of Bacillus anthracis, the bacterium that causes anthrax, together with crudely written notes declaring “Death to America, Death to Israel” and warning “We have this anthrax.”2United States Department of Justice. Amerithrax Investigative Summary
The letters arrived in two waves. The first, mailed around September 18, targeted media organizations: the New York Post, NBC News anchor Tom Brokaw, and the offices of American Media, Inc. in Boca Raton, Florida. The second wave, mailed around October 9, went to two Democratic U.S. Senators, Tom Daschle of South Dakota and Patrick Leahy of Vermont. The powder in the Senate letters was far more refined, with spores ground fine enough to float through the air and contaminate the postal facilities the letters passed through on their way to Washington.
Five people died of inhalation anthrax. Robert Stevens, a 63-year-old photo editor at AMI, was the first, on October 5, 2001. Two postal workers at the Brentwood mail processing facility in Washington, D.C. followed: Thomas L. Morris Jr., 55, on October 21, and Joseph P. Curseen Jr., 47, the next day. Kathy T. Nguyen, a 61-year-old hospital employee in New York City, died on October 31. The final victim was Ottilie Lundgren, a 94-year-old woman in Oxford, Connecticut, who died on November 21 from cross-contaminated mail despite having no direct connection to any of the targeted letters.2United States Department of Justice. Amerithrax Investigative Summary Seventeen others contracted cutaneous or inhalation anthrax and survived.1Federal Bureau of Investigation. Amerithrax or Anthrax Investigation
How the FBI Investigated the Case
The Amerithrax Task Force paired roughly 25 to 30 full-time investigators from the FBI, the U.S. Postal Inspection Service, and other agencies with federal prosecutors. Over the life of the case, the task force conducted more than 10,000 witness interviews across six continents, issued over 5,750 grand jury subpoenas, executed 80 searches, and recovered more than 6,000 items of evidence.1Federal Bureau of Investigation. Amerithrax or Anthrax Investigation
Early on, investigators did not know whether they were chasing a foreign state, an international terrorist group, or a domestic actor. Days after September 11, suspicion fell on al-Qaeda and governments with known biological weapons programs. Those leads went nowhere, and the task force eventually turned toward people inside the small American community that worked with anthrax.3United States Department of Justice. Amerithrax Investigative Summary
Lab analysis identified the material in the letters as the Ames strain of Bacillus anthracis, a highly virulent variety first isolated from a dead cow in Sarita, Texas in 1981 and never again found in nature. Before the attacks, only 15 U.S. and 3 foreign laboratories were known to possess it, and all existing stocks were in liquid or cell-culture form rather than powder.3United States Department of Justice. Amerithrax Investigative Summary Whoever sent the letters had the training and equipment to grow and dry the spores.
Tracing the attack powder to a specific source required the FBI to help invent a new discipline, microbial forensics. Working with government, university, and private labs, investigators developed genetic assays that could detect four unique mutations present in the attack material. Those mutations acted as a fingerprint. The task force collected 5,730 environmental samples from 60 locations and used whole-genome sequencing to narrow the field.1Federal Bureau of Investigation. Amerithrax or Anthrax Investigation By 2007, the trail led to a single parent material: a flask designated RMR-1029, held at the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) at Fort Detrick, Maryland. The flask contained all four of the genetic markers found in the letters.4National Center for Biotechnology Information. Review of the Scientific Approaches Used during the FBI’s Investigation of the 2001 Anthrax Letters – Section: 6.1. Introduction
The Steven Hatfill Mistake
Before the science pointed to RMR-1029, the FBI’s most visible target was Dr. Steven Hatfill, a former USAMRIID researcher. In the first four months of the case, eight people contacted the FBI to suggest he might be involved. Hatfill had worked at USAMRIID from 1997 to 1999 with broad access to the Ames strain, and a 2002 search of his apartment turned up anthrax production protocols and a simulant powder.3United States Department of Justice. Amerithrax Investigative Summary
By August 2002, Hatfill was publicly identified as a “person of interest.” Agents maintained visible surveillance, and the media coverage was constant. Hatfill, however, had left USAMRIID two years before the mailings and never had access to the area where RMR-1029 was stored. Once genetic analysis identified that flask as the source, Hatfill was conclusively excluded.3United States Department of Justice. Amerithrax Investigative Summary In June 2008, the government agreed to pay him $5.82 million to settle his lawsuit: $2.825 million in cash and a $3 million annuity paid out over 20 years. The Justice Department said the settlement was not an admission of liability.
The Case Against Bruce Ivins
The trail to RMR-1029 led to Dr. Bruce Ivins, a senior microbiologist at USAMRIID who had spent more than 20 years working on anthrax vaccines and was the flask’s primary custodian. The DOJ’s case rested on three pillars: the scientific link to his flask, suspicious behavior, and a plausible motive.3United States Department of Justice. Amerithrax Investigative Summary
Investigators documented Ivins making unauthorized late-night visits to his lab in the weeks before the mailings, during hours when no one else was there. When the FBI subpoenaed anthrax samples from labs across the country, a sample Ivins submitted appeared to come from a source other than RMR-1029, which investigators read as an attempt to mislead them. The Princeton, New Jersey mailbox had no obvious connection to Ivins until agents discovered it sat near an office of a college sorority with which he had a documented long-term obsession. Mental health records and colleagues described a man under increasing psychological strain, with shifting explanations when questioned.
The motive, as the DOJ laid it out, was career crisis. Ivins had devoted his professional life to an anthrax vaccine program that was failing. The vaccines were drawing criticism over potency problems and alleged links to Gulf War Syndrome, and by September 2001 USAMRIID was down to its last approved vaccine lot. Without a fix, Ivins would not have been allowed into the high-containment labs where he did his work. After the attacks, demand for the vaccine surged, funding returned, and his expertise became indispensable again.3United States Department of Justice. Amerithrax Investigative Summary
By the summer of 2008, federal prosecutors were preparing to seek an indictment under 18 U.S.C. § 2332a, which makes it a federal crime to use a biological weapon against people or property in the United States and, because five people died, authorized the death penalty.5Office of the Law Revision Counsel. 18 USC 2332a – Use of Weapons of Mass Destruction Ivins, recently released from inpatient psychiatric treatment, died by suicide on July 29, 2008. On February 19, 2010, the Department of Justice formally closed the investigation and released its investigative summary naming him as the sole perpetrator.1Federal Bureau of Investigation. Amerithrax or Anthrax Investigation
Why the Conclusion Remains Contested
The case against Ivins was never tested in court, and a 2011 review by the National Research Council, operating under the National Academy of Sciences, raised significant doubts about the strength of the scientific evidence. The committee’s central finding was blunt: “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.”4National Center for Biotechnology Information. Review of the Scientific Approaches Used during the FBI’s Investigation of the 2001 Anthrax Letters – Section: 6.1. Introduction
The panel found that the genetic results were “consistent with” the attack spores coming from RMR-1029 but “did not definitively demonstrate such a relationship.” It took direct issue with the DOJ’s repeated public claim that RMR-1029 had been “conclusively identified” as the parent material, calling that language stronger than the science supported. The committee also found the evidence surrounding the disputed sample Ivins submitted weaker than the investigative summary suggested, noting roughly a one-percent chance that an honest sample from RMR-1029 could have produced the same test results.4National Center for Biotechnology Information. Review of the Scientific Approaches Used during the FBI’s Investigation of the 2001 Anthrax Letters – Section: 6.1. Introduction The reviewers also noted that the FBI was at times uncooperative, giving minimal responses and deflecting questions as beyond the panel’s scope.
None of that exonerates Ivins. The DOJ’s case rested on behavioral and circumstantial evidence alongside the genetics, and the panel did not evaluate the behavioral evidence. What the review established is that the strongest public claims the government made about the scientific proof do not hold up to independent peer review, and the absence of a trial means no part of the case was ever subjected to adversarial cross-examination.
What Changed in U.S. Lab Security
The attacks exposed how loosely the United States regulated access to dangerous pathogens. Before 2001, Ivins had unrestricted after-hours access to his lab, and no system tracked who entered or when. Congress responded with the Public Health Security and Bioterrorism Preparedness and Response Act of 2002, which strengthened the Select Agent Program governing possession, use, and transfer of the most dangerous biological agents and toxins.6eCFR. 42 CFR Part 73 – Select Agents and Toxins
Under the current rules, any lab possessing select agents must register with the federal government, and every individual with access must pass a security risk assessment conducted by the Attorney General. Facilities must maintain written security plans, implement at least three physical security barriers around storage areas, and ensure law enforcement response to an alarm within fifteen minutes. Registration must be renewed every three years, and violations can draw civil penalties from the HHS Inspector General.6eCFR. 42 CFR Part 73 – Select Agents and Toxins That federal framework simply did not exist when the anthrax letters were mailed.