The FBI marched out a panel of outside scientific experts in an effort to end lingering doubts on whether Dr. Bruce Ivins was solely responsible for the attacks that killed five people and shook a nation already reeling from the Sept. 11 terrorist attacks on New York and Washington.

In briefings first for scientific journals and then for the news media, the FBI laid out what one official described as a “body of powerful evidence” after nearly seven years of investigation on the origin of the anthrax sent through the U.S. mail system and on the alleged perpetrator.

The FBI earlier this month released federal court documents that outlined its case against Ivins, a researcher and an anthrax expert at the U.S. Army Medical Research Institute of Infectious Diseases or USAMRIID in Maryland.

Ivins killed himself late last month just as prosecutors prepared to charge him with murder for committing the attacks. His attorney has said he was innocent. Several prominent scientists have questioned the FBI’s case against Ivins and the scientific backing for it. “I want to see the data. I want to see the valid scientific links made,” said Dr. C. J. Peters, a virologist at the University of Texas Medical Branch in Galveston, who worked at USAMRIID until 1990.

Critics have questioned the evidence against Ivins, partly because FBI investigators mistakenly focused for years on another scientist at Fort Detrick, Steven Hatfill. Hatfill was never charged and the government agreed in June to pay him US$5.85 million to settle a lawsuit.

“Obviously, looking at it in hindsight, we would do things differently today,” FBI Assistant Director Vahid Majidi said when asked whether the FBI should have kept the sample. “Were we perfect? Absolutely not. We’ve had missteps. Those are the lessons learned.”