The Federal Bureau of Investigation (FBI) in the United States is coming under increasing pressure to reveal the evidence it has connecting scientist Bruce Ivins who died in an apparent suicide last week, to the Anthrax attacks in the U.S. in 2001.
Years of painstaking investigation apparently traced the anthrax in the poisoned letters to a single flask of the bacteria at the Army biodefense laboratory at Fort Detrick, where Dr. Inins worked.
The FBI says 'microbial forensics', the use of biochemical clues, was employed to track the anthrax back to its source.
However working out just who was responsible for the anthrax letters would have also relied on more traditional investigative methods and would have included interviewing colleagues and family members, searching houses and cars, carrying out surveillance and making assessments of individuals personalities.
The suspicion is that most of the evidence is possibly in the main circumstantial as apparently at least 10 scientists had regular access to the laboratory and its anthrax stock not counting visitors from other institutions.
It has also been reported that workers at laboratories in Ohio and New Mexico received anthrax samples from the same flask at the Army laboratory.
Sometime in 2006 Dr. Ivins appears to have come under intense surveillance and every aspect of his life and work were examined; but it is only since his suicide last week, that FBI officials have revealed they were about to charge him with sending the anthrax letters, which killed five people.
Dr. Ivins was a respected microbiologist with 30 years of experience at the United States Medical Research Institute of Infectious Diseases at Fort Detrick, reports say he was popular in his neighborhood, a Red Cross volunteer and an amateur juggler and musician who played at his church.
But according to FBI investigators Dr. Ivins had a history of alcohol abuse, and an interest in pornography and was obsessed with university Kappa Kappa Gamma sorority houses.
As the investigation continued some of Dr. Ivins colleagues felt the FBI's methods were increasingly coercive, as scientists and family members were placed under what almost appears to be attempts at intimidation.
Many involved were left with the daunting impression that Dr. Ivins was singled out partly because of his personal weaknesses and because the FBI had to pin the attacks on someone, a view which carries some credit because despite the suggested implicating evidence, Dr. Ivins was neither charged or arrested.