Justice Department officials claim that Bruce Ivins, 62, a US government bio-weapons scientist, posted envelopes containing anthrax spores to members of Congress and the media in the aftermath of the September 11th terrorist attacks, spreading fear across America.
Mr Ivins took an overdose of sleeping pills after what his family and friends describe as persecution by the FBI, which told him he was about to be charged with murder. He worked at the Fort Detrick military base facility in Frederick, Maryland.
On Wednesday, Justice Department officials made their evidence against Mr Ivins public. Their case rested primarily on his possession of strands of anthrax genetically virtually identical to those used in the attacks, work in the laboratory at late hours during the months of the attacks and a history of paranoia.
Paul Kemp, Mr Ivins’s lawyer, described the case as “an orchestrated dance of carefully worded statements, heaps of innuendo and a staggering lack of real evidence – all contorted to create the illusion of guilt by Dr Ivins”.
Prosecutors could not place Mr Ivins in Princeton, New Jersey, where the letters were posted and there was no match between Ivins’s handwriting and that found in the anthrax laden letters.
Congressman Rush Holt of New Jersey questioned the government’s insistence that the complex attack could have been orchestrated by one individual.
Those close to Mr Ivins have suggested he was driven to suicide by investigators in much the same way as David Kelly, the British biological warfare expert, killed himself in 2003 amid a furore over justifications for the Iraq war.
The $15 million investigation lasted five years and led to a fruitless investigation of Steven Hatfill, another Fort Detrick researcher.
Mr Hatfill’s lawsuit against the US government was resolved in June with a $5.8 million settlement.
During a memorial service for Ivins on Wednesday at the Fort Detrick base, attended by hundreds of family, friends and colleagues, the dead researcher, who was married with two children, was praised as a dedicated servant to his country and a mentor to young scientists.