A decade after wisps of anthrax sent through the mail killed 5 people, sickened 17 others and terrorized the nation, biologists and chemists still disagree on whether federal investigators got the right man and whether the F.B.I.’s long inquiry brushed aside important clues.
Now, three scientists argue that distinctive chemicals found in the dried anthrax spores — including the unexpected presence of tin — point to a high degree of manufacturing skill, contrary to federal reassurances that the attack germs were unsophisticated. The scientists make their case in a coming issue of the Journal of Bioterrorism & Biodefense.
F.B.I. documents reviewed by The New York Times show that bureau scientists focused on tin early in their eight-year investigation, calling it an “element of interest” and a potentially critical clue to the criminal case. They later dropped their lengthy inquiry, never mentioned tin publicly and never offered any detailed account of how they thought the powder had been made.
The new paper raises the prospect — for the first time in a serious scientific forum — that the Army biodefense expert identified by the F.B.I. as the perpetrator, Bruce E. Ivins, had help in obtaining his germ weapons or conceivably was innocent of the crime.
Both the chairwoman of a National Academy of Science panel that spent a year and a half reviewing the F.B.I.’s scientific work and the director of a new review by the Government Accountability Office said the paper raised important questions that should be addressed.
Alice P. Gast, president of Lehigh University and the head of the academy panel, said that the paper “points out connections that deserve further consideration.”
Dr. Gast, a chemical engineer, said the “chemical signatures” in the mailed anthrax and their potential value to the criminal investigation had not been fully explored. “It just wasn’t pursued as vigorously as the microbiology,” she said, alluding to the analysis of micro-organisms. She also noted that the academy panel suggested a full review of classified government research on anthrax, which her panel never saw.
In interviews, the three authors said their analysis suggested that the F.B.I. might have pursued the wrong suspect and that the case should be reopened. Their position may embolden calls for a national commission to investigate the first major bioterrorist attack in American history.
But other scientists who reviewed the paper said they thought the tin might be a random contaminant, not a clue to complex processing. And the Justice Department has not altered its conclusion that the deadly letters were mailed by Dr. Ivins, an Army anthrax specialist who worked at Fort Detrick, Md., and killed himself in 2008 as prosecutors prepared to charge him.
Dean Boyd, a Justice Department spokesman, said the paper provided “no evidence whatsoever that the spores used in the mailings were produced” at a location other than Fort Detrick. He said investigators believe Dr. Ivins grew and dried the anthrax spores himself.
“Speculation regarding certain characteristics of the spores is just that — speculation,” Mr. Boyd said. “We stand by our conclusion.”
The tin is surprising because it kills micro-organisms and is used in antibacterial products. The authors of the paper say its presence in the mailed anthrax suggests that the germs, after cultivation and drying, got a specialized silicon coating, with tin as a chemical catalyst. Such coatings, known in industry as microencapsulants, are common in the manufacture of drugs and other products.
“It indicates a very special processing, and expertise,” said Martin E. Hugh-Jones, lead author of the paper and a world authority on anthrax at Louisiana State University. The deadly germs sent through the mail to news organizations and two United States senators, he added, were “far more sophisticated than needed.”
In addition to Dr. Hugh-Jones, the authors of the new paper are Barbara Hatch Rosenberg, a biologist, and Stuart Jacobsen, a chemist; both have speculated publicly about the case and criticized the F.B.I. for years.
In 2008, days after Dr. Ivins’s suicide, the bureau made public a sweeping but circumstantial case against him. Last year, the bureau formally closed the case, acknowledging that some scientific questions were unanswered but asserting that the evidence against Dr. Ivins was overwhelming.
Investigators found that the microbiologist had worked unusual late-night hours in his lab in the days before each of the two known anthrax mailings in September and October 2001; that he often mailed letters and packages under assumed names; that he had a history of homicidal threats and spoke of “Crazy Bruce” as a personality that did things he later could not remember.
Dr. Ivins had hidden from family and friends an obsession with a sorority — Kappa Kappa Gamma — with an office near the Princeton, N.J., mailbox where the letters were mailed. The F.B.I. recorded Dr. Ivins’s speaking ambiguously to a friend that he did “not have any recollection” of mailing the letters, that he was “not a killer at heart” and that “I, in my right mind, wouldn’t do it.”
Yet no evidence directly tied Dr. Ivins to the crime. Some of the scientist’s former colleagues have argued that he could not have made the anthrax and that investigators hounded a troubled man to death. They noted that the F.B.I. pursued several other suspects, most notoriously another former Army scientist, Dr. Steven J. Hatfill, whom the bureau eventually exonerated and paid a $4.6 million legal settlement.
In its report last February, the National Academy of Sciences panel sharply criticized some of the F.B.I.’s scientific work, saying the genetic link between the attack anthrax and a supply in Dr. Ivins’s lab was “not as conclusive” as the bureau asserted.
If the authors of the new paper are correct about the silicon-tin coating, it appears likely that Dr. Ivins could not have made the anthrax powder alone with the equipment he possessed, as the F.B.I. maintains. That would mean either that he got the powder from elsewhere or that he was not the perpetrator.
If Dr. Ivins did not make the powder, one conceivable source might be classified government research on anthrax, carried out for years by the military and the Central Intelligence Agency. Dr. Ivins had ties to several researchers who did such secret work.
The Government Accountability Office, the investigative arm of Congress, is conducting its own review of the anthrax evidence. Nancy Kingsbury, the official overseeing the project, said the agency had spoken with the paper’s authors and judged that “their questions are reasonable.”
Beyond the world of forensics, tin is a humdrum additive used to kill micro-organisms in products like paint, wood preservatives and even toothpaste. But microbiologists say that the nutrients and additives used to grow Bacillus anthracis, the anthrax bacteria, are typically free of tin.
So in late 2002, when the F.B.I. found significant quantities of tin in the mailed powders, it set out to find its source. By 2003, the bureau was calling tin “an element of interest” — echoing its terminology for human suspects — according to disclosures culled from 9,600 pages of F.B.I. documents by The Times.
Over the years, the bureau performed hundreds of tests to explore tin’s use in microbiology and significance in the attack germs. It also hunted for clues to how the spores had become laced with silicon, which the United States had used decades ago as a coating in germ weapons. In 2005, scientists at an internal F.B.I. symposium called tin a possible fingerprint of the attack germs.
After that, the forensic clue disappeared from public discussion, except for a passing mention in a 2009 press release. “Although the chemical fingerprint of the spores is interesting,” the release said, “it was not relevant to the investigation.”
In the end, the F.B.I. — without alluding to its private tin labors — declared publicly that the attack germs had no special coating, saying that conclusion supported its finding that Dr. Ivins had grown and dried the spores alone, using standard equipment in his lab at Fort Detrick.
Several anthrax scientists who reviewed the new paper at the request of The Times said they believed it neglected the possibility that the tin and silicon were meaningless contaminants rather than sophisticated additives.
Johnathan L. Kiel, a retired Air Force scientist who worked on anthrax for many years, said that the spores “pick up everything” and that the silicon might be residue of a commercial product used on laboratory glassware to keep spores from sticking. He said tin might even be picked up from metal lab containers, though he has not tested that idea.
It doesn’t have to be some super-secret process,” Dr. Kiel said. Other experts suggested that the tin might have come from anti-foam products, disinfectants or water.
The trouble with such conjecture is that the F.B.I. spent years testing for tin in microbiology lab supplies — and reported none, according to bureau documents.
Dr. Gast, the head of the National Academy of Sciences panel, noted that her group strongly recommended that future investigations of the attacks examine the government’s classified work on anthrax.
She called access to secret records “an important aspect of providing more clarity on what we know and what we don’t know.”
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