Two new investigations conducted in the course of the summer have called into question the claim by the Justice Department and the FBI that government scientist Bruce Ivins was the sole perpetrator of the anthrax letter attacks that killed five people in the fall of 2001.

Ivins committed suicide in 2008 after the FBI publicly targeted him as its main suspect, prosecutors announced they were preparing an indictment, and the scientist was removed from his job at the US Army Medical Research Institute of Infectious Diseases at Fort Detrick in Frederick, Maryland. USAMRIID is the main US germ warfare laboratory, and the 62-year-old Ivins was a leading researcher into possible anthrax vaccines.

An investigation conducted by McClatchy News Service, the PBS program “Frontline” and the Pro Publica consortium explored gaps in the official FBI investigation. Some of the findings were summarized in an article by McClatchy October 11, the same day that “Frontline” began its fall season with an examination of the case against Ivins.

The McClatchy-Frontline investigation did not challenge much of the circumstantial evidence against Ivins, including his history of mental illness and his lifelong obsession with the college sorority Kappa Kappa Gamma.

Ivins had a pattern of conduct, including long, overnight drives to the sites of various KKG houses, which dovetailed with the actions he would have had to take as the anthrax attacker. The anthrax letters were initially placed in a mailbox in Princeton, New Jersey, on the same block as the sorority’s local office, a seven-hour round-trip drive from Ivins’ home in Maryland.

But the probe found that much of the forensic evidence against Ivins was less compelling, or even questionable. For example, Justice Department lawyers acknowledged in a court filing July 15 that the sealed area in the lab controlled by Ivins did not contain the equipment required to create the refined powder form of anthrax used in the mailings. Lab scientists normally studied the anthrax in a liquid form.

Prosecutors claimed that Ivins had deliberately withheld evidence by sending in a false sample of his lab’s anthrax stocks when requested by investigators into the 2001 mailings. But on three other occasions, according to the McClatchy investigation, Ivins supplied the FBI anthrax samples that could be linked genetically to the anthrax used in the attacks, suggesting that he was actually cooperating with the probe, not seeking to sabotage it.

The FBI laid stress on work records that showed Ivins, after working little overtime at Ft. Detrick, spent dozens of hours alone in the lab at night during August, September and October 2001, the months when he allegedly prepared the anthrax mailings. “Frontline” reported, however, that this was a selective reading of Ivins’ work record, and that a broader measure showed him working heavy overtime nearly every month, without an unusual spike just before the anthrax attacks.

The second investigation was reported October 9 by the New York Times, and will be published shortly in the Journal of Bioterrorism & Biodefense. The three scientists who authored the new study argue that a chemical analysis of anthrax powder found in the second set of letters, mailed out in October 2001, “indicates a very special processing, and expertise.”

This is particularly due to the presence of tin in the anthrax, which the FBI initially focused on as important, but later claimed was insignificant. The tin could be a byproduct of complex processing of the anthrax spores, something that Ivins was believed unable to do, at least without assistance. The authors suggest that either Ivins was innocent, or there are other co-conspirators who have not been identified.

One of the main puzzles in the anthrax investigation has been the sharp difference between the comparatively rough spores sent in the first group of letters to media outlets, including the Sun tabloid, the New York Post and NBC News, and the better-prepared, purer and far more dangerous spores sent in subsequent letters to two prominent Senate Democrats, then-Majority Leader Thomas Daschle and Judiciary Committee chairman Patrick Leahy.

The three scientists are Martin E. Hugh-Jones, an anthrax expert from Louisiana State University, Barbara Hatch Rosenberg, a biologist, and Stuart Johnson, a chemist. Rosenberg played a prominent role in the initial stages of the investigation, correctly insisting that a domestic American government source was the most likely, not a foreign terrorist, although she mistakenly focused on Steven Hatfill, another USAMRIID scientist, who was later cleared.

The case against Ivins remains inconclusive, in large measure because of the long delay in identifying him. The Bush administration initially sought to link the attacks to its campaign to prepare the political climate for launching its war of aggression against Iraq.

Even when the investigation shifted to a US source for the anthrax, Ivins himself was one of the main consultants for the FBI for several years, despite being identified as a potential suspect by at least one former colleague who knew of his psychological instability. Because of his suicide, Ivins was never questioned in detail about the allegations outlined in lengthy FBI affidavits released to the public after his death.

There is ample evidence, however, that USAMRIID was grossly negligent in relation to its own security and the security of the American population that its research was ostensibly to protect. The result is that the only known case of a terrorist attack on American soil using biological weapons was conducted using a strain of anthrax developed at the Army’s own germ warfare laboratory.

Long married, with two children, Ivins repeatedly sought help from psychiatrists and counselors and was taking what one report called “a battery of antidepressant and antipsychotic drugs,” even while working every day with some of the deadliest substances known to science. One psychiatrist who treated him in the late 1990s told a colleague that Ivins was the “scariest” patient he had ever known.

Ivins was, at best, completely unfit psychologically for the high-stress environment of a bioweapons facility. Over the years, he openly discussed his inner demons with Army psychiatric counselors, without any action being taken against him, or any precautions to protect his co-workers and the public.

Ivins continued to work at USAMRIID even after he told a therapist he had plotted to poison a female co-worker and had obtained a quantity of cyanide, only changing his mind at the last minute. He described himself as an “avenging angel of death.”

When Ivins filled out an Army medical form in 1987, he placed question marks next to a series of listed symptoms of mental health problems, including “Memory Change,” “Trouble with Decisions,” “Hallucinations,” “Improbable Beliefs” and “Anxiety.” In 2000 he told a counselor he was prey to “paranoid, delusional thoughts” and had impulses to harm others.

But according to an Army source, cited by author David Willman in his book, The Mirage Man: Bruce Ivins, the Anthrax Attacks, and America’s Rush to War, “Dr. Ivins was never evaluated by USAMRIID for mental fitness.”

No US government investigation is likely to clear up the ongoing mystery of Ivins’ role in the anthrax attacks. Aside from the overriding political imperative of concealing as much as possible the connection between US germ warfare experiments and the anthrax attacks, the Justice Department has an impossibly conflicted legal position, insisting that Ivins acted alone, while maintaining that the Army was not negligent in allowing a highly unstable individual to have access to deadly anthrax spores.

These contradictions came to a head this summer in the $50 million lawsuit by Maureen Stevens, widow of Robert Stevens, a photo editor at the Sun tabloid, who was the first fatality in the 2001 anthrax attacks.

Justice Department lawyers suggested that Ivins might have produced the anthrax spores elsewhere than at Ft. Detrick. They filed papers claiming that “Ivins’ actions were not foreseeable to his supervisors at USAMRIID,” and hence “the United States should not be held liable for his actions.”

As one newspaper summarized the position: “In trying to minimize USAMRIID’s liability, government lawyers have had to walk a fine line, because the FBI says Ivins produced the anthrax powder at the facility while the civil lawyers are arguing it could have been prepared elsewhere.”