Representatives from nongovernmental organizations were supposed to sit quietly in the gallery as the delegates to a 4-week conference last summer in Geneva debated how to strengthen the Biological and Toxin Weapons Convention (BTWC) protocol. But that rule didn't stop molecular biologist Barbara Hatch Rosenberg from plopping herself down in a seat on the main floor. "I just walked in; nobody said anything," explains Rosenberg, who serves as chair of the Federation of American Scientists' (FAS's) working group on biological weapons verification. Members of the U.S. delegation were unhappy with the ad hoc seating arrangement, however, and forced her to move back to the gallery. 

Rosenberg's supporters and detractors already knew she was a hard-nosed and vocal activist who's unmovable once she takes a stand. "Barbara obviously makes no bones about her views," says Stephen Morse, an epidemiologist at Columbia University in New York City and a longtime friend. A government scientist who's battled Rosenberg behind tt for years puts a sharper edge on his description of her: "What she brings [to discussions] is an attitude."

That attitude has helped Rosenberg become one of the most visible critics of the FBI's investigation into the anthrax mailings last fall that killed five people and sickened at least 17 others. Less predictably, she also has become the leading nongovernment authority on who might have committed the crimes. Coming soon after the 11 September terrorist attacks, the mailings heightened the country's sense of vulnerability from abroad. But within weeks, Rosenberg asserted in a very public setting that the attacker was an American - specifically, a scientist with access to a federal lab that studies biological agents. The FBI's actions in the case have since converged with that profile, in particular, shining a spotlight on [Steven Jay Hatfill (born 1953)], a microbiologist who earlier this month vehemently proclaimed his innocence and accused the government and the media of ruining his life (Science, 16 August, p. 1109).

How did a 70-something academic - she's an environmental science professor at the State University of New York (SUNY),  Purchase - and bioweapons expert come to take on such a prominent role in this manhunt? Rosenberg professes surprise at the attention she's received, saying simply, "From what I knew the FBI knew, I knew they should be farther along" in their investigation. "That's why I began making statements."

Her motivation, she says, is to deter future assaults by helping solve the first deadly bioweapons attack within the United States. But her profile of the attacker also jibes with other stances she has taken. They include support for a protocol to strengthen the BTWC by advocating inspections to assess bioweapons production-a protocol from which the United States recently walked away (Science, 24 August 2001, p. 1415). She also opposes building more bioweapons labs.

Profiling the attacker. The anthrax letters that struck down and disrupted lives in New York, Florida, New Jersey, Connecticut, and Washington, D.C., last fall embodied the fears of Rosenberg and many other bioweapons experts, who had long warned that the country was ill prepared to handle such an attack. Her 2 decades of work in bioweapons control have given Rosenberg deep ties in the community; almost immediately following the attacks, she began receiving unsolicited tips from U.S. scientists whose connections with federal programs prevented them from speaking publicly.

By early November, Rosenberg says that certain clues, including signs that the anthrax strain had come from the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) at Fort Detrick, Maryland, convinced her that the perpetrator was an American. She went public with those thoughts on 21 November (2001) at a BTWC meeting in Geneva, asserting that New York City "has just been attacked, first by foreign terrorists, then by an American using a weaponized biological agent."

Rosenberg declines to explain why she chose that venue. But her voice rises in anger when she recalls how U.S. officials refused to join with other delegations at the November meeting. "[The U.S. was] accusing everyone else of having bioweapons, when the attack was coming from our program. ... I felt that it was necessary to point out."

Rosenberg came to believe that the scientist-perpetrator didn't intend to kill - after all, she says, the attacker warned that the letters contained anthrax or that the recipients should take penicillin-but rather nursed a grievance against the government for unfairly neglecting the U.S. bioweapons program. Since November, her theories have been widely disseminated over the Internet and in the media.

Earlier this year, Rosenberg wrote that the FBI had a suspect in mind but was reluctant to pursue him because "the suspect knows too much and must be controlled forever from the moment of arrest." She has since grown more circumspect about a possible conspiracy, saying, "I can only speculate as to why" the FBI hadn't been more aggressive.

That view still doesn't sit well with some scientists, although few are willing to criticize her in public. "My feeling is that if there is such a conspiracy, the FBI is not a part of it," says Steven Block, a biophysicist at Stanford University who has advised the U.S. government on bioweapons. Some scientists also felt that it wasn't a coincidence that Rosenberg's profile of the attacker fit one person. "She just seems to be too anxious to pin this on [Hatfill]," says [Dr. Peter B. Jahrling (born 1946)], a senior USAMRIID researcher, who says Rosenberg's comments about the case led him to decide early on that she had Hatfill in mind. Rosenberg maintains that she never named Hatfill or anyone else in comments to 2 the FBI or in her statements.

Rosenberg zealously preserves the anonymity of her sources, saying only that they are government scientists and other insiders. Those within and outside government labs agree that her sources seem knowledgeable. Jahrling, however, suggests that Rosenberg, doesn't have many friends in the government's biodefense labs because she opposes their planned expansion. Any expansion, she has argued, just adds to the pool of scientists with the means to pull off another bioweapons attack.

Both admirers and detractors agree thats he has pushed the FBI forward. "Without question, she's influenced this investigation," says Block, who also strongly suspects that the culprit, if not a U.S. citizen himself, has ties to the U.S. bioweapons program. Privately, scientists who support Rosenberg praise her for taking NEWS FOCUS on what they call a thankless job.

Rosenberg, whom the conservative Weekly Standard ridiculed as "the Miss Marple of SUNY/Purchase" in a recent article, maintains that the importance of finding out who sent the anthrax-tainted letters demanded her involvement and that her celebrity is purely accidental. Mark Wheelis, a microbiologist at the University of California, Davis, and a member of the FAS working group that Rosenberg runs, agrees that she generally shuns the limelight. But her determination, he notes, serves her well here: "The toughness is not part of her normal manner; it's a reserve she can draw on when it's called for."

And what if she's wrong? Rosenberg concedes that interrogating Hatfill might not help the FBI crack the case. But she quickly reverts to character. Even if that's true, she says, "the broad principles and the things I've said, I stand behind."