The science behind the U.S. government's investigation into the 2001 anthrax mailings does not rule out the possibility that the spores used in the attacks came from a source other than the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) in Frederick, Maryland. That's the conclusion of a just-released  National Academies' review of the scientific evidence related to the case, which was formally closed by the Federal Bureau of Investigation (FBI) and the Department of Justice in February 2010, more than 9 years after the letters killed five people and terrorized the nation.
The FBI announced in August 2008 that the attacks had been carried out by U.S. Army researcher Bruce Ivins using spores that he derived from a flask at USAMRIID. Ivins committed suicide days before the FBI was about to go public with the charges. Ivins's supporters maintain that he was innocent. In the absence of a trial, there was considerable public pressure on the government to conduct an independent review of the FBI's investigation. In September 2008, the FBI asked the National Academies to review the science behind the case.
Although the Academies review does not pass judgment on the guilt or innocence of Ivins, it says that the scientific case against him is not as ironclad as the FBI and DOJ have claimed. The FBI put out a statement this morning in response to the Academies report, pointing out that scientific analysis—although a key element of the investigation—was not the only thing that agents used to reach a conclusion in the case.
"The FBI has long maintained that while science played a significant role, it was the totality of the investigative process that determined the outcome of the anthrax case. Although there have been great strides in forensic science over the years, rarely does science alone solve an investigation," the statement reads. "The scientific findings in this case provided investigators with valuable investigative leads that led to the identification of the late Dr. Bruce Ivins as the perpetrator of the anthrax attacks."