A panel of prominent scientists is casting new doubt on scientific evidence that was a key part of the FBI's case against Bruce E. Ivins, the deceased Army scientist accused of carrying out the deadly 2001 anthrax attacks.
The National Research Council, in a report issued Tuesday, questioned the link between a flask of anthrax bacteria in Ivins's lab at Fort Detrick, Md., and the anthrax-infested letters that killed five people and sickened 17 others.
The Justice Department has said genetic testing conclusively linked the letters to spores in the flask - labeled RMR-1029 - found at the laboratory, where Ivins was a longtime researcher before committing suicide in 2008. The government closed the case last year after concluding that Ivins had single-handedly prepared and mailed the deadly anthrax spores, an incident that terrorized a nation still reeling from the Sept. 11, 2001 terrorist attacks.
"The scientific link between the letter material and flask number RMR-1029 is not as conclusive as stated in the DOJ Investigative Summary,'' said the $1.1 million report by the council, which was commissioned by the FBI. The document added, however, that the "genetic evidence is consistent with and supports an association between the RMR-1029 flask.''
The report, while praising the FBI's energetic pursuit of emerging science in the investigation, offered another possible explanation for the apparent link between the letters and the Ivins flask and said it "was not rigorously explored.''
The 190-page document by the research arm of the National Academy of Sciences also said the FBI's scientific methods in collecting samples of the strain of anthrax used in the attacks were "not optimal,'' and it said the authors could not verify the government's contention that only Ivins and a select group of scientists possessed the required expertise to prepare the spore-laden letters.
"This shows what we've been saying all along: that it was all supposition based on conjecture based on guesswork, without any proof whatsoever,'' said Paul Kemp, a lawyer who represented Ivins in negotiations with federal prosecutors who were preparing to charge him before his death. Kemp called for congressional hearings into the investigation.
The report makes no judgment about Ivins's guilt or innocence, and federal law enforcement officials on Tuesday stood behind their contention that Ivins was the anthrax killer. They pointed to what they said was overwhelming evidence linking him to the attacks, including e-mails and recorded conversations showing an increasingly agitated Ivins seeking to implicate colleagues while misleading investigators about his ability to make the deadly anthrax powder.
Lab records from Fort Detrick revealed that Ivins uncharacteristically logged dozens of hours late at night just before the anthrax envelopes were sent and that he was inexplicably absent during long stretches when investigators think he drove to New Jersey to mail them.
"The FBI has long maintained that while science played a significant role, it was the totality of the investigative process that determined the outcome of the anthrax case,'' the FBI and Justice Department said in a joint statement. "Although there have been great strides in forensic science over the years, rarely does science alone solve an investigation.''
The statement said the FBI had used science that was "innovative and groundbreaking" and that the report "provides valuable guidance" and "better prepares the FBI to respond to attacks of a similar nature in the future. ''
But the long-anticipated report reignited a debate that has been simmering among some scientists and others who have questioned the strength of the FBI's evidence against Ivins.
The extensive eight-year FBI probe, which spanned six continents, has included missteps, including the public naming of Ivins's colleague Stephen Hatfill as a "person of interest" in the investigation. The FBI later apologized to Hatfill.
"This report entirely undercuts the conclusion that RMR-1029 was the source and that Ivins was the perpetrator,'' said Meryl Nass, an anthrax expert and physician at Mount Desert Island Hospital in Maine. "That evidence was totally critical to their case,'' said Nass, who added that hundreds of people had access to the flaks in Ivins's lab. Federal investigators have said they investigated and ruled out all possible other suspects.
The report did endorse a key conclusion reached by FBI scientists: that the anthrax spores used in the mailings had not been altered, either genetically or chemically. That appeared to rule out the possibility that the spores were "weaponized" or manipulated to make them more deadly.
Some scientists have pointed to oddly elevated levels of silicon in the spores as an indication that the deadly powder was enhanced by someone with knowledge of advanced bioweapons techniques. The panel's findings, however, appeared to support the theory that the spores were produced by one or more individuals working alone, and were not the product of a state-run bioweapons program.
The proximity of the anthrax attacks to Sept. 11 had also fueled concern of possible terrorist involvement in the anthrax mailings. And the report reveals that the FBI and intelligence officers collected samples from an overseas site "because of information about efforts by al-Qaeda to develop an anthrax program.''
The report said the tests turned out to be negative but that the evidence was inconsistent, and it called for further review. It said the committee that prepared the report was provided "only fragmentary information" about the tests "very late in our study."
Federal law enforcement officials, speaking on condition of anonymity to discuss sensitive information, said the committee was offered a classified briefing to explain why federal investigators determined there was no evidence of anthrax at the overseas site. The committee declined because it only wanted information that could be made public, the officials said.
Staff reporter Joby Warrick and staff researcher Julie Tate contributed to this story.