Photo: Joseph Persichini (center), Assistant Director in Charge of the FBI's Washington Field Office, with U.S. Attorney Jeff Taylor (left), District of Columbia, and Chief Postal Inspector Alexander Lazaroff of the U.S. Postal Service, explains recent developments in the government's Amerithrax case.

The story of the U.S. government's investigation into Dr. Bruce E. Ivins and his suicide by drug overdose as federal authorities closed in to arrest him last week has all the suspense of a big-budget Hollywood legal drama. And as is often the case with such dramas, this one may not have a neat ending.

However, the public may find some answers. Due to intense public interest in the case, a federal judge earlier this week took the extraordinary step of unsealing documents pertaining to the Justice Department's investigation of the case. Now analysis of the evidence can begin and perhaps some kind of closure can be found in the episode U.S. Attorney for the District of Columbia, Jeffrey Taylor, called "the worst act of bioterrorism in U.S. history."

The Justice Department has released a catalog of documents that detailed its case against Ivins. Based on this evidence, the department believes Ivins was the sole person responsible for the attacks and that "we could prove his guilt to a jury beyond a reasonable doubt," Taylor said at a press conference yesterday. However, Taylor continued, "Had Dr. Ivins been tried, he would have been presumed innocent until proven guilty."

Based on the indications of the evidence and the suicide of the primary suspect in the case, the Justice Department has begun the process of concluding the seven-year investigation. The investigation, known as "Amerithrax," involved 17 FBI Special Agents and 10 U.S. Postal Inspectors in more than 75 searches and more than 9,100 interviews.

And while the case against Ivins is strong, it is mostly circumstantial. However, there are a few pieces of forensic evidence indicating Ivins was the source of the attacks. That evidence includes the flask, from which the anthrax spores used in the attacks were taken, and for which Ivins was responsible, as well as pre-franked envelopes with printing defects traceable to a post office in Frederick, Md.

First, in early 2005, researchers identified the genetically-unique parent material of the anthrax spores used in the mailings as a single flask of spores, known as 'RMR-1029,' that was created and solely maintained by Dr. Ivins at the United States Army Medical Research Institute for Infectious Diseases in Frederick, Md. "This means that the spores used in the attacks were taken from that specific flask, regrown, purified, dried and loaded into the letters. No one received material from that flask without going through Dr. Ivins." Taylor said. "We thoroughly investigated every other person who could have had access to the flask and we were able to rule out all but Dr. Ivins," he continued.

Furthermore, Taylor said, Ivins was a renowned expert in the production and purification of anthrax spores. He was one of a handful of scientists with the capability to create spores of the concentration and purity used in the attacks. The affidavits allege that, not only did Dr. Ivins create and maintain the spore batch used in the mailings, but he also had access to and experience using a lyophilizer. A lyophilizer is a sophisticated machine that is used to dry pathogens and can be used to dry anthrax. "We know others in Dr. Ivins' lab consulted him when they needed to use this machine," Taylor said.

As for the envelopes used in the attacks, they were all pre-franked and sold only at U.S. post offices during a nine-month period in 2001. An analysis of the envelopes revealed several print defects in the ink on the