An acclaimed government scientist who assisted the federal investigation of the 2001 anthrax mailings said Tuesday that he erred seven years ago when he told top Bush administration officials that material he examined probably had been altered to make it more deadly.
The scientist, Peter B. Jahrling, had observed anthrax spores with the aid of an electron microscope at the government's biological warfare research facility at Ft. Detrick, Md.
On Oct. 24, 2001, Jahrling was summoned to the White House after reporting to his superiors what he believed to be signs that silicon had been added to anthrax recovered from a letter addressed to then-Senate Majority Leader Tom Daschle (D-S.D.).
The presence of silicon was viewed with alarm because the material, if artificially added to the anthrax, would make it more buoyant in air and more capable of penetrating deeply into the lungs.
"I believe I made an honest mistake," Jahrling said in response to questions e-mailed to him for this article, adding that he had been "overly impressed" by what he thought he saw under the microscope.
"I should never have ventured into this area," said Jahrling, who is a virologist, referring to his analysis of the anthrax, which is a bacterium. Jahrling's initial analysis -- and his briefing of officials at the White House -- was first detailed in a 2002 book by bestselling author Richard Preston.
Although Jahrling was careful in 2001 not to implicate Iraq or any other regime in the mailings, others used his analysis to allege that the silicon perhaps linked the letters to Iraqi President Saddam Hussein.
Inhaled anthrax can kill at a rate of 80% to 90% unless patients are treated quickly with an antibiotic.
Jahrling's comments Tuesday came soon after a congressional hearing at which FBI Director Robert S. Mueller III announced that he was arranging for an outside review of scientific findings that helped the bureau conclude that another scientist at Ft. Detrick, Bruce E. Ivins, perpetrated the deadly mailings. The review is to be overseen by the National Academy of Sciences, Mueller said.
FBI scientists and outside experts hired by the bureau to analyze the anthrax recovered from the mailings announced Aug. 18 that although they had found silicon, it occurred within the spores naturally and was not added.
In challenging those experts, one journalist reminded them that Jahrling, among other scientists, had concluded otherwise.
Some critics of the FBI investigation have asserted that Ivins lacked the skills to have "weaponized" the anthrax with any additive that enhanced its virulence.
At Tuesday's hearing, a member of the House Judiciary Committee, Rep. Jerrold Nadler (D-N.Y.), pressed Mueller anew about how the silicon got into the spores.
After being informed of the events at the hearing, Jahrling renounced his earlier analysis.
"In retrospect," Jahrling said, "I believe I was mistaken and defer to the experts."
Ivins, 62, a civilian bacteriologist for the Army, died July 29 after ingesting a massive dose of prescription Tylenol 3.
Attorneys Ivins had hired to defend him against criminal charges being prepared by the Justice Department have said that they would have won his acquittal if the case had gone to trial.
In 2001, Jahrling briefed a roomful of officials at the White House, including Atty. Gen. John Ashcroft, Mueller and Tom Ridge, President Bush's secretary of Homeland Security.
The next day, the Washington Post published a front-page article headlined "Additive Made Spores Deadlier" that reported:
"The presence of the high-grade additive was confirmed for the first time yesterday by a government source familiar with the ongoing studies, which are being conducted by scientists" at Ft. Detrick.
The article said that the United States, the former Soviet Union and Iraq were "the only three nations known to have developed the kind of additives that enable anthrax spores to remain suspended in the air, making them more easily inhaled" and more deadly.
At the time, Jahrling was employed as the senior civilian scientist at the U.S. Army Medical Research Institute of Infectious Diseases, within Ft. Detrick.
Jahrling is a past winner of the Secretary of Defense Meritorious Civilian Service Award.
Michael P. Kortan, a spokesman for Mueller, said after the congressional hearing that the FBI was seeking the outside review while maintaining "full confidence in our scientific approach."
"Consideration of an outside review began before any public disclosure of the scientific aspects of the investigation," Kortan said.
Times researcher Janet Lundblad in Los Angeles contributed to this report.