Trail of Odd Anthrax Cells Led FBI to Army Scientist

Bureau officials decided to look again. Ivins, they found, had turned in two samples from his lab. The first was rejected because Ivins had not followed the FBI's detailed instructions and had used the wrong type of test tube. Ivins was asked for a second sample, and this time, investigators deduced, he tried to deceive them. He bypassed his exclusive reserve of spores -- the one he used in his experiments -- and turned in something different. Later tests to determine the origin of the substitute sample came up blank. "Our experts could not tell us where it came from," a senior investigator said.

FBI agents searched Ivins's lab and found the flask labeled RMR-1029. Tests showed it was pure, highly concentrated Ames anthrax bacteria, with genetic mutations identical to those in the attack strain.

Back at the bureau's Washington field office, agents were reconstructing the history of RMR-1029. A giant flow chart, covering most of a wall, recorded each discovery about the origins of the spores and what Ivins did with them. But the agents wondered: Could others, besides Ivins, have gotten access to the flask of spores?

The question drives much of the skepticism about the FBI's case. At a news conference in August, bureau officials estimated that as many as 100 people potentially had access to the biocontainment lab where Ivins kept his collections. Investigators have maintained that other possible suspects were ruled out, but they have never explained how. It is one of the gaps that independent experts and lawmakers have raised since Ivins's death.

In interviews, FBI officials said the list of 100 names included USAMRIID scientists as well as anyone with even a tenuous connection to Ivins's lab, such as visitors or janitors. Each person was investigated, though most could not have gotten to the spores under any reasonable scenario the investigators could construct.

For one thing, no one besides Ivins seems to have known where they were kept. The plain, triangle-shaped storage flask was one of many kept in plastic tubs inside a refrigerated storage room in Ivins's restricted lab. It had only a handwritten label -- RMR-1029, shorthand for "reference material received, No. 1029." When spores were needed for experiments, Ivins alone would retrieve them. "His own people who worked with him on a daily basis didn't know which flask it was," Langham said.

Initially, agents thought Ivins divided his spores into two flasks and kept one in a different building, which would have increased the number of people with potential access. That belief was based on a lab notebook entry that turned out to be erroneous, agents said.

Still, dozens of people were cleared at various times to enter USAMRIID's Building 1425, where Ivins worked and kept his spore collection. Each had to be investigated, even those who lacked the basic knowledge to handle highly lethal bacteria. "An animal handler might have had access," said Bannan, "but he would not have had the capability. And he probably would have expired by now."

Simply obtaining the microbes would have been only the first hurdle. The FBI is convinced that the bioterrorist did not merely steal spores from RMR-1029, but also regrew them and converted them into a highly concentrated powder. And then he repeated the process.

Differences between the two grades of anthrax powders used in the attacks -- the earlier batch sent to New York news outlets was coarser and darker than the powder mailed to the Senate -- confirm that there were at least two production runs. Bureau officials knew they were looking for someone who had repeated access to Ivins's flask as well as talent for sophisticated spore preparations.

The list of suspects narrowed, officials said, until only one was left: Ivins. Ivins alone created and controlled the distinctive collection of anthrax cells that provided the seeds for the attacks. And he was the undisputed master at manipulating the bacteria into dense concentrations of deadly spores. While graduate school microbiologists could have performed most of the tasks, Ivins had the experience and the "good set of hands" required to achieve a spore preparation of such quality, a government scientist said.

"When you go to the true experts and ask them how many people can develop [anthrax spores] into something with this purity and this concentration, they shake their heads," said Montooth, the lead Amerithrax investigator. "Some will say there are perhaps six. Others will say maybe a dozen."