The pressure on Ivins was extreme, a high-risk strategy that has failed the FBI before. The government was determined to find the villain in the 2001 anthrax attacks; it was too many years without a solution to the case that shocked and terrified a post-9/11 nation.
The last thing the FBI needed was another embarrassment. Overreaching damaged the FBI's reputation in the high-profile investigations: the Centennial Olympic Park bombing probe that falsely accused Richard Jewell; the theft of nuclear secrets and botched prosecution of scientist Wen Ho Lee; and, in this same anthrax probe, the smearing of an innocent man - Ivins' colleague Steven Hatfill.
In the current case, Ivins complained privately that FBI agents had offered his son, Andy, $2.5 million, plus "the sports car of his choice" late last year if he would turn over evidence implicating his father in the anthrax attacks, according to a former U.S. scientist who described himself as a friend of Ivins.
Ivins also said the FBI confronted Ivins' daughter, Amanda, with photographs of victims of the anthrax attacks and told her, "This is what your father did," according to the scientist, who spoke only on condition of anonymity because their conversation was confidential.
The scientist said Ivins was angered by the FBI's alleged actions, which he said included following Ivins' family on shopping trips.
Washington attorney Barry Coburn, who represents Amanda Ivins, declined to comment on the investigation. An attorney for Andy Ivins also declined to comment.
The FBI declined to describe its investigative techniques of Ivins.
FBI official John Miller said that "what we have seen over the past few days has been a mix of improper disclosures of partial information mixed with inaccurate information and then drawn into unfounded conclusions. None of that serves the victims, their families or the public."
The FBI "always moves aggressively to get to the bottom of the facts, but that does not include mistreatment of anybody and I don't know of any case where that's happened," said former FBI deputy director Weldon Kennedy, who was with the bureau for 34 years. "That doesn't mean that from time to time people don't make mistakes," he added.
Dr. W. Russell Byrne, a friend and former supervisor of Ivins at the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick, Maryland, said he had heard from other Ivins associates that investigators were going after Ivins' daughter. But Byrne said those conversations were always short because people were afraid to talk.
"The FBI had asked everybody to sign these nondisclosure things," Byrne said. "They didn't want to run afoul of the FBI."
Byrne, who retired from the lab four years ago, said FBI agents interviewed him seven to 12 times since the investigation began - and he got off easy.
"I think I'm the only person at USAMRIID who didn't get polygraphed," he said.
Byrne said he was told by people who had recently worked with Ivins that the investigation had taken an emotional toll on the researcher. "One person said he'd sit at his desk and weep," he said.
Questions about the FBI's conduct come as the government takes steps that could signal an end to its investigation. On Wednesday,in the 2001 attacks.
The government is expected to declare the case solved but will keep it open for now, according to two U.S. officials who spoke on condition of anonymity because of the ongoing investigation. Several legal and investigatory matters need to be wrapped up before the case can officially be closed, they said.
Some questions may be answered when documents related to the case are released, as soon as Wednesday. For others, the answers may be incomplete, even bizarre. Some may simply never be answered.
It is unclear how the FBI eliminated as suspects others in the lab who had access to the anthrax. It's not clear what, if any, evidence bolsters the theory that the attacks may have been a twisted effort to test a cure for the toxin. Investigators also can't place Ivins in Princeton, New Jersey, when the letters were mailed from a mailbox there.
Richard Schuler, attorney for anthrax victim Robert Stevens' widow, Maureen Stevens, said his client will attend Wednesday's FBI briefing with a list of questions.
"No. 1 is, 'Did Bruce Ivins mail the anthrax that killed Robert Stevens?"' Schuler said, adding, "I've got healthy skepticism."