WASHINGTON — Microbiologists, like nature, abhor a vacuum, and in the absence of an FBI arrest in last fall's anthrax attacks, some of the nation's top scientists are offering their own theories.
In memos making their way around the Internet and in hallway conversations at professional conferences, leading scientists — many fearful that an unsolved case will encourage other bioterrorists — are applying their deductive reasoning to the anthrax-laced letters that killed five people and spread a new level of fear about biological warfare.
Their theories are full of intrigue: A disgruntled scientist. A covert government project gone awry. An accomplice to the Sept. 11 hijackers who stayed behind to mail the letters after their planes hit the Pentagon and the World Trade Center. Right-wing extremists stockpiling the deadly material in anticipation of a visit from the Internal Revenue Service.
"We all have our pet theories," said Jason Pate, a bioterrorism expert at the Monterey Institute of International Studies. "But none seems to fit the facts exactly."
The FBI has been working aggressively on the case, conducting thousands of interviews and hundreds of lab tests in consultation with some of the world's top scientific experts and in concert with the Centers for Disease Control and Prevention and other agencies.
Some scientists applaud the effort — crediting agents with catching on quickly to the complexities of microbiology. But others, led by Barbara Hatch Rosenberg of Purchase College, State University of New York, think the FBI has been, as she put it, "dragging its feet."
They are scornful of an FBI e-mail sent to 32,000 members of the American Society for Microbiology in January — three months after the attacks stopped — asking scientists for their help in locating the culprit, possibly a loner with access to an American lab. They wonder why the FBI outreach came so late, and so broadly, when people with expertise and access to anthrax materials is probably closer to 200 scientists.
For its part, the FBI privately takes a dim view of the analyst's armchair speculation. Mindful of their own mistakes in targeting Wen Ho Lee for spying in 1999 and Richard Jewell for the Atlanta Olympics bombing in 1996, the FBI is eager to get this one right.
Rosenberg, a molecular biologist, began the scientific sleuthing in Feburary when she posted an article on the Web site of the Federation of American Scientists, www.fas.org/bwc, for which she has directed a panel on bioweapons for the last 10 years. In the article, she writes that the anthrax discovered in the letters mailed to two U.S. senators was so refined that it contained one trillion spores per gram, characteristic of the "weaponized" anthrax made by U.S. defense labs.
Given the technical expertise required to produce that kind of anthrax, and the small universe of scientists with that knowledge, Rosenberg estimates that perhaps fewer than 40 people could be suspects.
She believes that the perpetrator is one of her own: a disgruntled American scientist.
"He must be angry at some biodefense agency," she writes. "He is driven to demonstrate, in a spectacular way, his capabilities and the government's inability to respond."
At the heart of her case is a conspiracy theory, a conviction that the slowness of the investigation can be explained only by some big secret that the government wants to keep hidden for as long as possible.
"He is cocksure that he can get away with it," she writes of the perpetrator. "Does he know something that he believes to be sufficiently damaging to the United States to make him untouchable by the FBI?"
The BBC cited Rosenberg in a news report this month suggesting that there could have been a secret government program to test the practicalities of sending anthrax through the mail. "Some very expert field person might have been asked to investigate the consequences of mailing anthrax and it would have been left to him to decide exactly how to carry it out," she said. "The result might have been a project gone badly awry if he decided to use it for his own purposes."
The FBI fumes at any suggestion it would deliberately sit on evidence, pointing out that it arrested one of its own, agent-turned-Russian spy Robert Philip Hanssen, as soon as it learned of his betrayal.
Still — while not ruling out any theories — the FBI's own public profile of the anthrax killer sounds a lot like Rosenberg's.
In its e-mail in January to microbiologists, the FBI asked them to be on the lookout for a loner. "The perpetrator might be described as 'standoffish' and likely prefers to work in isolation as opposed to a group/team setting," it said. "It is possible this person used off-hours in a laboratory or (borrowed) equipment to produce the anthrax."
The evidence, however, points in a different direction for two theorizing medical professionals: Tara O'Toole and Thomas V. Inglesby of the Johns Hopkins University Center for Civilian Biodefense Strategies.
Assessing a medical case in Florida, in which one of the Sept. 11 hijackers sought treatment for a leg wound in June, O'Toole and Inglesby concluded that the skin lesion might have been caused by anthrax. That was the conclusion too of the attending physician, Dr. Christos Tsonas of the Holy Cross Hospital in Fort Lauderdale, Fla., but it was reached only after reviewing his notes taken while treating Ahmed Ibrahim Al Hanzawi for what appeared to be a simple, if unusual, leg injury.
In a two-page memo for the FBI, O'Toole and Inglesby said the anthrax diagnosis was "the most probable and coherent interpretation of the data available." O'Toole says that to believe that someone other than the hijackers and their accomplices hatched the anthrax plot would be to accept a lot of coincidences.
The FBI says that there are no blood tests, cultures or pictures that would help resolve the Florida case. While it does not rule out any leads or directions, the FBI leans toward the theory of a domestic terrorists. But Al Hanzawi lived with other hijackers in Boca Raton, Fla., the same city where the first anthrax victim worked. Exposure to anthrax can cause black skin lesions like the one on Al Hanzawi's leg. And Mohammed Atta, another hijacker, visited the Belle Glade State Municipal Airport, north of Fort Lauderdale, to look at crop-dusting equipment, possibly as a conveyance for biological weapons.
To analysts including Pate of the Monterey Institute, the improbability of so many coincidences "makes your eyebrows go up."
But Pate has his own theory. Manager of a terrorism task force at the Institute's Center for Nonproliferation Studies, he says American right-wing extremists are plausible suspects.
The anti-government cliques, wary of official agencies and with a fascination for biological agents, tend to stockpile such weapons, he said.
Pate's theory could explain the targets of the anthrax letters — two liberal Democratic senators (Majority Leader Tom Daschle of South Dakota and Judiciary Chairman Patrick J. Leahy of Vermont) and the news media (CBS, NBC and The New York Post) — all hated by the fringe cults.
Some people question whether the armchair sleuths have more than cursory knowledge of the case.
"I think that Barbara Hatch Rosenberg and Tara O'Toole may both be guilty of some degree of over-speculation," said one researcher who did not want to offend his colleges by being named.
Still, given the similarities between the mind-set of scientists and detectives, the urge to speculate might be irresistible.
"Dr. Rosenberg thinks it's a disgruntled worker conspiracy. Drs. O'Toole and Inglesby think it's Sept. 11 accomplices. I think it's some right-wing extremists," Pate said. "But maybe it's a disgruntled right-wing extremist scientist accomplice."