Bruce E. Ivins, the late microbiologist suspected in the 2001 anthrax attacks, had attempted to poison people, and his therapist said she was "scared to death" of him, according to court testimony that emerged yesterday.

Social worker Jean C. Duley testified at a court hearing in Frederick on July 24 in a successful bid for a protective order from Ivins - who committed suicide five days later - that he "actually attempted to murder several other people."

Ivins took a fatal dose of acetaminophen, the active drug in Tylenol, as federal authorities monitored his movements and prepared to charge him with the murder of five people who died from anthrax poisoning in the weeks after the Sept. 2001 terror attacks.

An audio recording of the court session was obtained by The New York Times and posted it on its Web site.

"As far back as the year 2000, the respondent has actually attempted to murder several other people, either through poisoning. He is a revenge killer. When he feels that he's been slighted or has had - especially toward women - he plots and actually tries to carry out revenge killings," Duley said.

She added that Ivins "has been forensically diagnosed by several top psychiatrists as a sociopathic, homicidal killer. I have that in evidence. And through my working with him, I also believe that to be very true."

Ivins, 62, who worked at an Army biodefense laboratory at Fort Detrick, took his own life Tuesday as federal authorities were closing in after investigating him for more than a year in connection with the deaths of five people poisoned by anthrax sent through the mail.

Answers to one of the nation's highest profile unsolved mysteries are in documents that could be released as early as this week - and help explain how the government chased the wrong suspect for years.

Prosecutors were mulling this weekend whether to close the anthrax poisoning investigation, possibly as early as tomorrow or Tuesday. If that happens, court documents detailing newly developed scientific evidence that recently led the government to Ivins may be unsealed.

Five people died and 17 others were sickened when anthrax-laced letters began showing up at congressional offices, newsrooms and post offices soon after Sept. 11, 2001.

After wrongly investigating Army scientist Steven Hatfill, the FBI more than a year ago began looking at Ivins, who worked at the same military lab.

Two U.S. officials said victims and their survivors could be briefed as early as Tuesday on the final piece of the bioterrorism attacks that confounded the government.

The Justice Department attributed the break in the case to "new and sophisticated scientific tools" that cost the FBI about $10 million. Investigators said the science focused, in part, on how the anthrax strains were handled and who had access to it at the time of the mailings.

FBI scientists were able to isolate strains used in the attacks, and determined they were not as common as previously thought. And that led investigators to Ivins.

Had the same process been available years ago, it would have cleared Hatfill much earlier, according to two people familiar with the FBI investigation who spoke on condition of anonymity because the case is not officially closed.

The Army refused yesterday to say whether it had been reviewing the security clearance of the chief suspect in the anthrax attacks.

Ivins was removed from his lab in Maryland by police on July 10 and temporarily hospitalized, according to court records, because it was feared that he was a danger to himself and others.

But it was unclear whether he was still employed by the lab at the time of his death Tuesday.

That raises the question of whether Ivins still had his security clearance and, if so, how he kept it, given that his social worker said Ivins had been viewed as homicidal and sociopathic by his psychiatrist.

Army spokesman Paul Boyce declined to comment on Ivins' case.

Boyce didn't respond to a question on what type of clearance microbiologists at the lab would have to hold.

David R. Franz, a former commander of the Army's lab biological warfare labs at Fort Detrick, said yesterday that he thought it was "very important that the FBI present their case against Bruce and not just state that the investigation was over because it was him and he's gone."

Franz added, "I'm concerned about what closing this case without conclusive evidence might do to harm our life sciences enterprise. ... I think we as Americans need to see the proof."

Among the unanswered questions is why the anthrax was sent. The FBI was investigating whether Ivins, renowned for his work developing anthrax vaccines and treatment, released the toxin to test those cures. Ivins was one of several scientists named in an application for a vaccine patent 18 months before the attacks.

Another puzzle is what finally led the FBI to focus on Ivins a year or so ago. Ivins attracted some attention for conducting unauthorized anthrax testing in the six months following the anthrax mailings, but the FBI focus stayed on Hatfill.

As Ivins' name emerged, so did a portrait of a conflicted, troubled man. His friends knew him as the man who played music at church, a Red Cross volunteer who was an avid juggler and gardener.

Others saw a darker side, such as what Duley described in filing for a restraining order in a Maryland court.

"Client has a history dating to his graduate days of homicidal threats, plans and actions towards therapists," Duley wrote in court documents last week, adding that his psychiatrist had described him as homicidal and sociopathic.

Maryland's chief medical examiner, Dr. David Fowler, confirmed Saturday that Ivins died Tuesday morning at Frederick Memorial Hospital; that the cause of death was found to be an overdose of acetaminophen; and that it was ruled a suicide based on information from police and doctors.