Analysis

What is not in dispute: the attacks happened, the anthrax was real and deadly, and the letters themselves were recovered. What remains legitimately disputed is whether the FBI correctly identified the perpetrator.

The Amerithrax Investigation

The FBI's Amerithrax task force was one of the largest and costliest investigations in the agency's history, eventually involving over 600,000 investigator hours. The first major suspect was Steven Hatfill, an Army virologist; the FBI surveilled him intensively for years before quietly dropping him as a suspect. Hatfill sued the government for defamation and won a $5.8 million settlement in 2008.

The investigation then converged on Bruce E. Ivins, a senior biodefense researcher at the US Army Medical Research Institute of Infectious Diseases (USAMRIID) at Fort Detrick, Maryland. Ivins had worked on anthrax vaccines for decades and had legitimate access to the type of spore preparation believed to have been used in the letters. Under intense FBI pressure — the agency had begun telling colleagues and neighbours of Ivins that he was the likely culprit — Ivins died from an acetaminophen overdose on 29 July 2008, four days before prosecutors were reportedly prepared to indict him.

The FBI officially closed the case against Ivins in February 2010, releasing a 92-page summary asserting he was the sole perpetrator. The case rested heavily on a novel form of microbial forensics: investigators claimed that genetic "morphotype" variations in a flask of anthrax spores (RMR-1029) stored in Ivins's lab linked the attack anthrax to that specific source with scientific certainty.

The National Academy of Sciences Review

In 2011, the National Academy of Sciences released a comprehensive independent review of the FBI's scientific case. The panel's conclusion was careful but significant: the genetic and technical evidence was "consistent with" the attack anthrax originating from RMR-1029 but was "not as definitive as portrayed" by the Bureau. Critically, the NAS found that the Flask RMR-1029 held spores that had been distributed to multiple laboratories over the years — meaning several facilities had access to materially identical source material, not only Ivins's direct custody.

The report also noted methodological limitations: the morphotype analysis relied on techniques developed specifically for this case and had not been independently validated before being used as forensic evidence. The NAS stopped short of exonerating Ivins but made clear that the evidentiary chain was insufficient to definitively establish sole guilt beyond reasonable doubt.

What Is Confirmed

• The anthrax attacks occurred and killed five Americans.
• The anthrax was weapons-grade, refined to a high concentration of spores with an aerosol-optimised particle size.
• The anthrax strain was the Ames strain, used extensively in US government biodefense research.
• Flask RMR-1029 at USAMRIID was genetically consistent with the attack material.
• Ivins had access, expertise, and the opportunity (unsupervised late-night lab time in the weeks before the mailings).
• The FBI had zero physical evidence placing Ivins at the Trenton postbox; no witness saw him there.

What Remains Disputed

The "FBI framed Ivins" version — which circulated widely after his death — overclaims just as the FBI's certainty did. What is genuinely uncertain is whether Ivins acted alone, whether the investigation properly excluded other researchers with access to comparable material, and whether the suicide of the only named suspect before trial means the definitive truth will ever be established.

Some investigators and journalists (including former FBI agent Richard Lambert, who later sued the Bureau alleging evidence was mishandled) have argued the investigation was shaped by pressure to close a high-profile unsolved case after the Hatfill embarrassment. Ivins's own psychiatrist later publicly stated she believed he was dangerous and capable of the attacks; colleagues described him as brilliant, erratic, and obsessed with certain sorority symbols that appeared in the letters.

The Conspiracy Claims

After 9/11, early speculation claimed the anthrax came from an Iraqi source — connecting the letters to justifications for war. No evidence ever supported this; the Ames strain is American-origin. Separate claims alleged "inside government" involvement beyond Ivins. These broader government-conspiracy framings are not supported by the evidence and are assessed here as unsupported additions to an already legitimately disputed set of questions about the FBI's specific case.

Forensic Science, Alternative Suspects, and the Limits of the Case

The scientific centerpiece of the FBI's case against Ivins was the morphotype analysis of Flask RMR-1029. Investigators identified four genetic variants in the attack spores and argued these variants were found only in samples traced to RMR-1029. But the National Academy of Sciences panel, reviewing the same data in 2011, found that the statistical framework underlying this claim had not been validated before being used as forensic evidence. The panel noted that multiple laboratories had received material derived from RMR-1029 over the years, and the FBI had not fully mapped every institution that could have possessed comparable genetic material.

Before converging on Ivins, the FBI spent years investigating Dr. Steven Hatfill, a virologist with relevant expertise who had no connection to RMR-1029. The Bureau placed him under intensive physical surveillance, leaked his name to journalists, and publicly described him as a "person of interest." In 2008 a federal judge ruled the leaks violated the Privacy Act; Hatfill settled with the Justice Department for $5.82 million without admitting guilt. The Hatfill episode demonstrated that the FBI was capable of building an intense evidentiary narrative around a suspect who was ultimately cleared, which is a legitimate reason to apply scrutiny to its subsequent certainty about Ivins.

A separate analytical strand emerged from scientists outside the Bureau. Researcher Christos Tsonas and colleagues examined the silicon content of the attack spores and proposed that their preparation required specialized knowledge consistent with certain advanced biodefense programs. The FBI disputed this interpretation, arguing the silicon was an artefact of the sporulation process rather than an additive. No consensus was reached in the published literature.

Dr. Richard Lambert, the FBI agent who led the Amerithrax investigation for years before being reassigned, filed a whistleblower lawsuit in 2015 alleging the Bureau had withheld exculpatory evidence regarding Ivins and had suppressed alternative hypotheses. Lambert's lawsuit was dismissed on procedural grounds, but its existence underscores that the internal dissent about the case's conclusion extended to senior investigators.

The Ames strain used in the attacks was the standard research strain distributed to US biodefense laboratories from the 1980s onward. Genomic analysis published in 2008 in the journal Science confirmed that the attack anthrax carried a distinctive genetic signature linking it to a specific lineage within the Ames strain pool — an advance that significantly narrowed the suspect pool to laboratories working with that lineage. This genomic work was the most scientifically robust element of the investigation. However, even this finding was consistent with multiple institutions, not exclusively with Ivins's direct custody.

Verdict

Partially true: the attacks happened exactly as reported. The FBI's conclusion that Bruce Ivins alone was responsible is the product of a flawed and politically pressured investigation whose scientific foundations a National Academy of Sciences panel found to be overstated. This does not establish Ivins's innocence — the available evidence is consistent with his guilt — but it does mean the case as officially closed was not proven to the standard claimed.