WASHINGTON - Despite the Justice Department's pronouncement that government microbiologist Bruce Ivins unleashed the 2001 anthrax attacks that killed five people, three key questions about the case remain unanswered:
• Can the FBI prove that a flask of anthrax in Ivins' laboratory at Fort Detrick, Md., contained the same mutated strain of powder that was in the envelopes mailed to two U.S. senators?
• Did Ivins, who committed suicide last week, have the technical capability to produce that form of anthrax?
• Why, after he came under suspicion in 2005 or earlier, was Ivins allowed to continue working in the bioweapons laboratory at Fort Detrick?
As federal prosecutors and FBI agents moved to close the seven-year investigation, former employees at the U.S. Army Medical Research Institute of Infectious Diseases and other biological weapons experts Thursday expressed skepticism about the case that has been presented publicly.
The FBI said Wednesday that it had winnowed eight samples that contained all four of the genetic mutations in the anthrax-laced letters out of 1,000 anthrax samples from 16 laboratories and traced all eight to a batch in Ivins' lab that had the same "DNA fingerprint."
However, Jeffrey Adamovicz, who directed the bacteriology division at Fort Detrick in 2003 and 2004, said the FBI trail is "a little disturbing" because it relies on a common contaminant in laboratories and in the environment. While the FBI said it found a unique mutation of that contaminant, Adamovicz said, it has yet to say that this strain "was found in Dr. Ivins' lab and no one else's."
Donald Henderson, a scholar at the University of Pittsburgh's Center for Biosecurity who assisted the government investigation, said the FBI's case against Ivins "just doesn't add up." He said the FBI must produce its DNA evidence for scrutiny by scientists.
Some of Ivins' former colleagues, including Adamovicz, also dispute the FBI's assertion that he had the capability to mill anthrax spores and then bind them to silicon -- the form of anthrax that was mailed to then-Sen. Tom Daschle, D-S.D.
"Just because you're off your rocker doesn't mean you can make something that no one else in the world can make with the kind of equipment that's available," said Richard Spertzel, who worked in the lab for 21 years before retiring in 1987.
Another mystery is why Ivins wasn't escorted from the facility until last month when the FBI had discovered by 2005 that he had failed to turn over samples of all the anthrax in his lab.
Institute spokeswoman Caree Vander-Linden said that lab supervisors monitor their scientists' behavior and that, under a program implemented in 2003, all researchers undergo intrusive background checks.
But at most labs, unless scientists have been committed to a mental hospital, psychiatric issues don't factor into the security process. That's a policy decision that balances security and privacy rights.
In other developments:
• Government sources told the Washington Post that Ivins took several hours off from work on the day that the deadly letters were mailed in New Jersey.
• The FBI said in an affidavit that Ivins used a public library computer to read e-mail and read a website dedicated to the anthrax investigation on July 24, the day he was released from a two-week psychiatric hospital stay -- and just a few days before he killed himself.
• Sen. Charles Grassley, R-Iowa, and Rep. Rush Holt, D-N.J., frequent critics of the FBI, demanded the release of more documents and hearings.
The Associated Press, Washington Post and Los Angeles Times contributed to this report.