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It all depends on what is actually in the spore material. There is moderately compelling evidence that the material is just spores and therefore could be produced by many microbiologists.
However, there are so many conflicting reports that it can't be said with absolute certainty that the material is not highly engineered. If it is, then Spertzel is really scary and seems to just taunt the world from the neocon perspective. The Kelly quote even makes that part worse. Spertzel speaks with the voice of authority but always comes out with something that would support the neocon agenda--exactly in the way the attack was used to strengthen the case for invading Iraq.
The one early sample (New York Post) that was recovered could well be less pure, based on most reports I've read. The material that killed Robert Stevens wasn't recovered. He died of inhalation anthrax and coworkers also got inhalation anthrax. The building also was heavily contaminated, so that sample was probably fairly pure. The Daschle and Leahy samples were described as extremely pure.