For nearly seven years, scientist Bruce E. Ivins and a small circle of fellow anthrax specialists at Fort Detrick's Army medical lab lived in a curious limbo: They served as occasional consultants for the FBI in the investigation of the deadly 2001 anthrax attacks, yet they were all potential suspects. Over lunch in the bacteriology division, nervous scientists would share stories about their latest unpleasant encounters with the FBI and ponder whether they should hire criminal defense lawyers, according to one of Ivins's former supervisors. In tactics that the researchers considered heavy-handed and often threatening, they were interviewed and polygraphed...