Doubts remain as case against 'anthrax killer' is revealed

Prosecutors in Washington have made public the first details of their case against the government scientist suspected of carrying out the 2001 anthrax attacks. But doubt still persisted about the FBI's handling of the affair – including even whether Bruce Ivins was in fact responsible for the attacks that killed five people.

The evidence that emerges from affidavits released yesterday by the Justice Department after a seven-year investigation is powerful but essentially circumstantial. It will not be tested in court, as Dr Ivins, senior researcher at the government's bioweapons laboratory at Fort Detrick, Maryland, killed himself with a drug overdose as the government was preparing to indict him on charges that could carry the death penalty.

Perhaps most damning, Dr Ivins was said to be the custodian of a large flask of the deadly spores that had, as one affidavit said, a "certain genetic mutation" that was "identical" to the anthrax contained in the anthrax-laced letters sent to Congressional leaders and various media organisations in Washington, New York and Boca Raton, Florida.

He was also unable to explain some of his movements, including various late night work sessions in his lab, around the time the letters were sent in September and October 2001 – the first of them mailed exactly a week after the September 11 terrorist attacks. Other affidavits say he had "incredible paranoid thoughts," and a history of mental problems.

Dr Ivins, it is also alleged, submitted false samples for analysis by investigators. He also apparently sent out an email just before the anthrax warning that Osama bin Laden's al-Qa'ida organisation had both anthrax and the deadly sarin agent. The email contained language similar to the crudely written notes in the letters themselves. Finally, Dr Ivins is said to have made self-incriminating statements under questioning by investigators.

"We only started to focus on Dr Ivins in 2007," Jeffrey Taylor, federal attorney for the District of Colombia, told a press conference last night, after prosecutors had explained their findings to relatives of the victims, and most of the other 17 people infected by the anthrax spores but who survived.

"We believe that on basis of the evidence we collected, we could prove his guilt to a jury beyond reasonable doubt," Mr Taylor said. "We are confident that he was the only person responsible for the attacks." The evidence was circumstantial but compelling, a "chain of evidentiary items that lead to only one conclusion".

Even so, much remains unexplained. The envelopes in which the anthrax was sent "very probably" originated at a post office in Frederick, Maryland, where Dr Ivins maintained a PO box, investigators said. He also had the time to drive to Princeton, New Jersey, where the letters were postmarked, but Mr Taylor conceded there was no evidence actually placing him there.

At least equally baffling is motive. Investigators have suggested Dr Ivins sent out the letters to test whether a vaccine he was preparing worked. "He may have been trying to create a scenario whereby people realised they would need to take the vaccine," one official said. Others, however, point out that the scientist must have known the acute danger in which he was placing people. In the days following Dr Ivin's death, several colleagues have publicly insisted he was incapable of doing such a thing.

Officials flatly rejected suggestions yesterday that agents had hounded Mr Ivins for years, creating a pressure that eventually led him to take his own life.