WASHINGTON — Scientists behind the case against Bruce E. Ivins, who federal officials allege was solely responsible for the deadly anthrax mailings of 2001, publicly described their work for the first time Monday and said the spores had originated from a flask linked by investigators to the deceased Army scientist.
In two briefings with reporters spanning nearly four hours, the scientists provided new and sometimes clarifying details about the extensive testing that led prosecutors to the brink of filing murder charges against Ivins, who died of a prescription-drug overdose July 29. The briefings were intended to more fully explain the evidence against Ivins and address concerns about the reliability of the government's assertion that Ivins was the culprit.
But Ivins' attorney remained unconvinced, and a top government scientist acknowledged that some skeptics would never be satisfied.
"I don't think we're ever going to put the suspicions to bed," said Vahid Majidi, a chemist and assistant director of the FBI's weapons of mass destruction unit. "There's always going to be a spore on a grassy knoll."
Among the new details Monday was that, contrary to statements made over the years by other government officials, the mailed anthrax had not been coated with additives to "weaponize" it, or make it more deadly. Silicon was detected within the spores, said several of the eight scientists who met with reporters, but it occurred naturally, not as a result of weaponizing.
The silicon did not make the anthrax more buoyant when exposed to air, said James Burans, associate laboratory director of the National Bioforensic Analysis Center.
"The silicon would not have contributed to the fluid-like qualities of the anthrax powders," he said. But loading the powder into envelopes, and their handling by the Postal Service, would have made it more electrostatically charged and difficult to contain, he said.
Burans also said that high-speed mail processing machinery could have crushed the powder more finely -- evidenced by plumes that rose 30 feet above the floor at a postal annex in Washington.
On the other hand, he and the other scientists did not offer an exact explanation of how Ivins was able to prepare the fluffy, dry, powdered anthrax. Ivins, they said, could have used a lab-issue drier called a lyophylizer, but not necessarily.
However it was done, said Majidi, "it would have been easy to make these samples at" Ft. Detrick, Md., home of the Army's infectious diseases research facility.
Over the past several years, the FBI searched worldwide to gather 1,070 samples of deadly Ames-strain anthrax -- the type used in the mailings. Only eight of those anthrax samples contained four distinct genetic mutations -- the same mutations found in the mailings. And each of those eight samples, officials allege, could be traced to parent material known as RMR 1029 that was maintained by Ivins in a one-liter flask he controlled in a Ft. Detrick lab.
In addition to the far-reaching scientific efforts, investigators used conventional police work to exclude as suspects about 100 others who may have had access to RMR 1029 at Ft. Detrick and elsewhere.
In his view, Majidi said, the government amassed "a body of powerful evidence that allows us to conclude that we have identified the origin and the perpetrator of the 2001 [anthrax] mailings."
Starting in 1980, Ivins worked as a microbiologist at the Army's Medical Research Institute for Infectious Diseases, or USAMRIID, at Ft. Detrick. Both before and after the anthrax mailings in September and October of 2001, which killed five people and set off a wave of fear on the heels of the Sept. 11 terrorist attacks, he prepared spores used in experiments on animals in an effort to develop or improve vaccines against anthrax.
The parent material for the anthrax mailings -- the one flask of RMR 1029 -- was derived from a mixture of various batches of spores, originally totaling 164 liters, said Chris Hassell, a chemist who since June has headed the FBI's laboratory. Hassell said that Ivins produced RMR 1029 from spores shipped from 22 "production runs" at Ft. Detrick and from 13 runs received there from the government's Dugway Proving Ground in Utah.
When the FBI sought scientific help in analyzing powder recovered from the mailings, it turned to USAMRIID -- and to Ivins. Officials who addressed the media Monday acknowledged for the first time that Ivins had helped the FBI compose the "protocol" for early subpoenas that sought anthrax samples from USAMRIID scientists, including Ivins.
In February 2002, even before his subpoena arrived, Ivins submitted a sample that violated the protocol, the officials said. And because FBI officials concluded that the protocol violation would make Ivins' sample inadmissible in court, the bureau destroyed it. In April 2002, Ivins gave the FBI a second sample, which did not match the RMR 1029 parent strain.