The government's case was circumstantial but seemingly damning.
Army scientist Bruce Ivins had possession of purified anthrax spores linked to the deadly 2001 attacks. He worked alone.
He submitted false anthrax samples to FBI officials to throw investigators off his trail. He tried to frame unnamed co-workers and threatened to kill anyone who wronged him.
When investigators asked Ivins about his "late laboratory work hours," the brilliant yet deeply troubled 62-year-old didn't have an explanation.
As the circumstantial evidence mounted, authorities said, they were certain they had the perpetrator of the five anthrax poisoning deaths that followed closely after the airliner terror attacks of Sept. 11, 2001.
Then, when investigators told Ivins they were going to charge him in the deaths, he committed suicide.
"We regret that we will not have the opportunity to present evidence to the jury," U.S. Attorney Jeffrey Taylor said Wednesday as court documents in the case were unsealed and the government made its case publicly.
Ivins was solely responsible for the anthrax attacks, the government declared, saying only he had custody of highly purified anthrax spores with "certain genetic mutations identical" to the poison used in the attacks. Investigators also said they had traced back to his lab the type of envelopes used to send the deadly powder through the mails.
Ivins' attorney, Paul Kemp, said the government was "taking a weird guy and convicting him of mass murder" without real evidence.
Taylor conceded the evidence was largely, if not wholly, circumstantial. Noting that Ivins would have been entitled to a presumption of innocence, Taylor nevertheless said prosecutors were confident "we could prove his guilt to a jury beyond a reasonable doubt."
Portrait of increasingly desperate man
The newly released court records depict Ivins, who had been troubled by mental health problems for years, as increasingly desperate as he confronted the possibility of being charged.
"He said he was not going to face the death penalty, but instead had a plan to kill co-workers and other individuals who had wronged him," according to one affidavit. In e-mails to colleagues, Ivins described a feeling of dual personalities, the documents said.
The FBI's investigation had dragged on for years, tarnishing the reputation of the agency in the process. Investigators had long focused on Steven J. Hatfill, whose career as a bioscientist was ruined after then-Attorney General John Ashcroft named him a "person of interest" in the case in 2002. The government recently paid $6 million to settle a lawsuit by Hatfill, who worked in the same lab as Ivins.
Taylor said investigators concluded in 2005 that Hatfill couldn't have had access to a crucial flask of anthrax spores.
The prosecutor called the flask the murder weapon in the worst case of bioterror in the nation's history.
Authorities say that language Ivins used in an e-mail days before a second round of anthrax attacks was similar to the messages in anthrax-laced letters received soon after by Democratic Sens. Tom Daschle and Patrick Leahy.
In the e-mail, Ivins wrote that "Bin Laden terrorists for sure have anthrax and sarin gas" and have "just decreed death to all Jews and all Americans." The letters to Daschle and Leahy said: "WE HAVE THIS ANTHRAX . . . DEATH TO AMERICA . . . DEATH TO ISRAEL."
Private meetings with victims' families
Wednesday's documents were released as FBI Director Robert Mueller met privately with families of the victims of the attacks to lay out the evidence officials.
As for motive, investigators seemed to offer two possible reasons for the attacks: that the brilliant scientist wanted to bolster support for a vaccine he helped create and that the anti-abortion Catholic targeted two pro-choice Catholic lawmakers.
The events in Washington unfolded as a memorial service was held for Ivins at Fort Detrick, the secret government installation in Frederick, Md., where he worked. Reporters were barred.
More than 200 pages of documents were made public by the FBI, virtually all of them describing the government's attempts to link Ivins to the crimes.
"It is a very compelling case," said Rep. Chris Smith, R-N.J., who attended a briefing for lawmakers and staff.
Republican Sen. Charles Grassley of Iowa called for a congressional investigation.
The government material describes at length painstaking scientific efforts to trace the source of the anthrax that was used in the attacks.
Tracking the anthrax
It says that in his lab, Ivins had custody of a flask of anthrax termed "the genetic parent" to the powder involved — a source that investigators say was used to grow spores for the attacks on "at least two separate occasions."
Anthrax culled from the letters was quickly discovered to be the so-called Ames strain of bacteria, but with genetic mutations that made it distinct. Scientists developed more sophisticated tests for four of those mutations, and concluded that all the samples that matched came from a single batch, code-named RMR-1029, stored at Fort Detrick.
Ivins "has been the sole custodian of RMR-1029 since it was first grown in 1997," said one affidavit.
Powder from anthrax-laden letters sent to the New York Post and Tom Brokaw of NBC contained a bacterial contaminant not found in the anthrax-containing envelopes mailed to Leahy or Daschle, the affidavit said.
Investigators concluded that "the contaminant must have been introduced during the production of the Post and Brokaw spores," the affidavit said.
The documents disclosed that authorities searched Ivins' home on Nov. 2, 2007, taking 22 swabs of vacuum filters and radiators and seizing dozens of items. Among them were video cassettes, family photos, information about guns and a copy of "The Plague" by Albert Camus.
Investigators also reported seizing three cardboard boxes labeled "Paul Kemp ... attorney client privilege."
Ivins' cars and his safe deposit box also were searched.
According to an affidavit filed by Charles B. Wickersham, a postal inspector, the scientist told an unnamed co-worker "that he had `incredible paranoid, delusional thoughts at times' and 'feared that he might not be able to control his behavior.'"
A mental health worker who was involved in treating Ivins disclosed last week that she was so concerned about his behavior that she recently sought a court order to keep him away from her.
Allegations that Ivins sought to mislead investigators ran through the material made public.
A picture of deception
One FBI document said Ivins "repeatedly named other researchers as possible mailers and claimed that the anthrax used in the attacks resembled that of another researcher" at the same facility.
The name of the other researcher was not disclosed.
The documents painted a picture of Ivins seeking to mislead investigators beginning in 2002, when he allegedly submitted the wrong samples to FBI investigators.
It wasn't until more than two years later, in March 2005, that he was confronted with the alleged switch, according to U.S. Postal Inspector Thomas Dellafera, who added that Ivins insisted he had not sought to deceive.
The victims of the attacks had little in common.
Robert Stevens, 63, a photo editor at the Sun, a supermarket tabloid published in Boca Raton, Fla., was the first to die. Thomas Morris Jr. 55, and Joseph Curseen, 47, worked at a Washington-area postal facility that was a hub for sorting the capital's mail. Kathy Nguyen, 61, who had emigrated from Vietnam and lived in the Bronx, worked in a stock room at Manhattan Eye Ear & Throat Hospital. Ottilie Lundgren, 94, who lived in Oxford, Conn., was the last to die.