The media have reported that some biodefense scientists said Ivins couldn’t produce the powdered anthrax found in the letters, but at least one scientist said he could.
One problem is that the public does not know how the letters’ anthrax was produced, nor whether it contained an additive that promoted dispersion.
Anthrax is produced in liquid culture, and the methods for growing it are readily available in the open literature. However, in this form it does not make a good biological weapon. To cause serious infection it must be inhaled. For optimal effect, the spores need to stay airborne as long as possible, not bind to larger particles in the environment, and be of the right size. The method for producing anthrax that has been optimized for these properties is a closely held secret, as it should be.
It has been illegal to possess biological weapons since 1975; some people believe the possession of any dried anthrax is illegal. (The Biological Weapons Anti-Terrorism Statute of 1989, Title 18, USC 175 was amended on 10/24/01 to include possession without legitimate purpose as a violation.)
Although powdered anthrax was produced at Fort Detrick when the US had a biowarfare program, before 1970, no one still there was part of that program. Whether the letters’ anthrax was produced using Detrick’s old method or something else has not been made public.
In fact, even the scientific literature is contradictory regarding the use of an additive in the anthrax placed in letters. In August 2007, an FBI forensic scientist claimed there was no additive, while a colleague in September 2006 who worked with the material said there was. Media reports from 2001 indicated the spores contained an electrostatic charge, and it was thought this charge was a function of special processing. Now the FBI has indicated this is not so.
It is unlikely that Ivins knew how to prepare weaponized anthrax, but not inconceivable.
However, the amount he would have had to process was larger than needed for his animal experiments. Each letter is thought to have contained 2-3 trillion spores. I can’t recall his animals receiving more than about a million spores each. So roughly one million times as much anthrax was needed for the letters as for an animal experiment. Increasing the scale of fermentation should have been noticed. Drying anthrax would have been noticed, as there was no need to prepare any other anthrax specimens this way. Sudden use of a dryer for large samples would be suspicious. Post-drying processing for the letter anthrax likely took place; were the materials needed available to Ivins?
How the anthrax was produced and processed is crucial to solving the case, but the information is classified. The FBI’s failure to provide briefings to Congress and reliable information to the public means it may be impossible for those outside the investigation to independently evaluate the evidence in the case.