The trail that led to Bruce Ivins as the prime suspect in the 2001 deadly anthrax mailings ended when the government scientist died of a drug overdose in July as the FBI prepared to arrest him for the attacks. Six months later, the New York Times has published what it touted as "the deepest look so far at the investigation" of his role in the attacks based on interviewed with Ivins's friends, colleagues, anthrax experts and law enforcement officers involved in the probe.

The most surprising revelation: the long string of clues that Ivins, who worked in the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID), left behind dismissed by FBI agents trying to track the source of anthrax that killed five people, sickened 17 others and caused panic at a time when the wounds of the September 11 terrorist attacks were still fresh.

Among the many clues ignored, according to the Times: The Army learned that in December 2001 Ivins had secretly swabbed for anthrax spores outside his secure laboratory space at USAMRIID (a federal biodefense research lab at Fort Detrick in Frederick, Md., where he had worked for 18 years) but failed to report the incident immediately to his superiors at the lab as per standard procedure. Records later showed, the Times reports, that Ivins had worked "unusually late hours" in his lab for several nights before each of the anthrax mailings.

Ivins, though highly skilled at handling anthrax, did not become a suspect even after the FBI determined that the anthrax had not been weaponized and likely came from a domestic source, as Scientific reported in September.*

In one chilling anecdote in the Times story, Nancy Haigwood, now director of the Oregon National Primate Research Center and a former classmate of Ivins at the University of North Carolina, recounts receiving an e-mail from Ivins containing a photograph of him working with anthrax in the laboratory without gloves--a very dangerous safety breach. "I read that e-mail," she said, "and I thought, 'He did it.' "

* Erratum (2/1209): The original sentence stated that the FBI determined that the anthrax had been weaponized.