All the available evidence indicates that the source of the mailed anthrax, or the information and materials to make it, is a US government program.

1. ANTHRAX STRAIN
 
• All letter samples contain the same strain of anthrax, corresponding to the AMES reference strain in the N. Arizona State University database (which has been used for identification). That Ames sample was obtained from Porton Down (UK) in the mid-90's (the sample was marked "October 1932"); Porton had gotten it from Fort Detrick.

 
• A 2000 paper by M. Hugh-Jones, PJ Jackson, P. Keim et al says that the Ames strain played a central role in the US BW program. Hugh-Jones says he learned that from David Huxsoll, Former Commander, USAMRIID. He also says Vollum 1B was the strain stockpiled (at least in the early days of the US BW program).

 
• The Ames strain is highly virulent and is used now in the US biodefense program for testing vaccines etc.

 
2. WEAPONIZATION
 
• The form in the senate letter: fine particles, very narrow size range (1.5-3 microns diameter, typical of the US process), treated so it won't clump and will float. The weaponization process used was extraordinarily effective.

 
• The extraordinary concentration (one trillion spores per gram) and purity of the letter anthrax is believed to be characteristic only of material made by the US process.

 
• A reporter who writes on anthrax vaccine has privately confirmed that four labs have told him that under the electron microscope the sample looks just like material obtained by UNSCOM in Iraq. The Iraqi material was spray-dried BT; it was not milled. Milled samples contain debris and are therefore distinguishable. It can thus be concluded that the EM observations indicate that the letter anthrax was not milled. The US process did not use milling.

 
• The US weaponization process is secret-Bill Patrick, its inventor and holder of five patents on the process, says it involves a COMBINATION of chemicals.

 
• The Armed Forces Institute of Pathology (Washington DC) is studying the material using an energy dispersive X-ray spectroscope, which can detect the presence of extremely tiny quantities of chemicals; traces of materials have been found.

 
• The Senate sample contains an unusual form of silica, a drying agent used only in the US process. It does not contain bentonite (used by the Iraqis).

 
• At least one other chemical additive, used in the US process, has been identified in the sample.

 
• All the letters probably contained the same material. The clumping of the anthrax in the two letters mailed on Sept 18 (to NBC and the NY Post) probably resulted from the letters getting wet in the course of mail processing or delivery, according to Army scientists.

 
3. ANTHRAX PRODUCTION
 
• A study of genetic drift at certain locations in anthrax has been carried out at Northern Arizona State University. The results give an idea of how many times the letter anthrax had replicated, in comparison to the reference strain-ie, whether it was grown on a very large scale (as in a State program) or on a very small scale, as would be likely if recently made by a terrorist. Word has it that the results are consistent with small scale. This suggests that the anthrax may have been made specifically for the letters.

 
• Analysis of trace contaminants could also indicate the scale/method of production (ie, liquid medium, in a fermenter, or solid medium, on petri dishes, a likely method for small-scale preparation).

 
4. OTHER ANALYSES
 
• It has been reported that the complete sequence has been determined for the genomes of both the anthrax used in the Florida attack and the Ames reference strain to which it corresponds. This work was done under government contract by the Institute for Genomic Research, a private non-profit organization. The results have not been made public but they are in government hands and there has been no retraction of the oft-repeated statement that the anthrax matches the Ames reference strain. In addition, the Ames reference strain may be a mixture of types, as sequencing has revealed to be the case for another anthrax strain. If so, the proportions of the mixture may differ from lab to lab and could be used to identify the source.

 
• Senator Bob Graham, Chairman of the Senate Intelligence Committee, said in late October that investigators can identify with great certainty which lab produced the anthrax, but it will be a laborious, time-consuming process. (Chicago Tribune, 27 Oct 01).

 
5. SOURCE LOCATION
 
• Contrary to early speculation, there are only about twelve laboratories known to have the Ames reference strain. Of these, no more than half might have the capability for weaponization by the American process. These include both government labs and government contractor labs. Excluding those not in the East (where the letters were mailed on two dates) would lower the number further.

 
6. INFORMATION REGARDING THE PERPETRATOR
 
• Analysts believe the letters were not written by a Middle-Easterner. The FBI publicly conjectures that the perpetrator was a lone, male domestic terrorist, obviously one with a scientific background and lab experience who could handle hazardous materials.

 
• The perpetrator must have received anthrax vaccine recently (it requires a yearly booster shot), whether or not he made the material himself, because filling the letters was a dangerous operation. The vaccine is in short supply and is not generally accessible. Vaccination records must be available.

 
• The perpetrator appears to be a forensic expert. He has successfully covered every personal trace.

 
7. TIMING
 
• There was only 1 week between 11 Sept and Sept. 18th, when the first two letters (and probably a letter, never found, to AMI) were postmarked. This suggests that the anthrax was already in hand before Sept 11.

 
• Did the perpetrator have advance knowledge of the Sept 11 attacks? Secretary of Defense Rumsfeld has said that he does not believe al Qaeda was responsible for the anthrax attack, and other public officials have increasingly indicated that the perpetrator was probably domestic.

 
8. PUBLIC STATEMENTS
 
• At first, US officials provided miscellaneous bits of information, some conflicting; then denied some of the earlier information, then clammed up. They now have a great deal of information that has not been made public. Under pressure from leaks, they have started a gradual release of information again.

 
• The US rejected a UN resolution condemning the anthrax attack, on the grounds that it could have been domestic terrorism.

 
• The Secretary of Health and Human Services said in October that some of the relevant information is classified, and some is restricted by the FBI.

 
• John Bolton, Under Secretary of State for Arms Control and International Security, spoke on Nov. 19 at the opening of the five-yearly Review Conference of the Biological Weapons Convention in Geneva. At a press conference following his talk, he said "We don't know, as I say in the statement, at the moment, in a way that we could make public, where the anthrax attacks came from." This statement, as well as other information, indicates that US officials do know where the anthrax came from.

 
• The FBI says it is now investigating government and contractor laboratories possessing the Ames strain and weaponization capabilities.

 
9. MOST LIKELY HYPOTHESIS
 
• The perpetrator is an American microbiologist who has access to recently-weaponized anthrax or to the expertise and materials for making it, in a US government or contractor lab. He does not live in or near Trenton, which is a stop on the Amtrak line that runs along the East coast. If he is smart enough to handle anthrax he is smart enough not to mail it from his home town. Trenton is probably accessible to him, however.

 
• The anthrax in the letters was made and weaponized in a US government or contractor lab. It may have been made recently rather than in the US BW program before Nixon terminated the program in 1969.
• Weaponization of dry anthrax after 1972, when the BWC was signed, could be construed as a violation of the BWC.
• The Ames reference strain in the N. Arizona collection, which matches the letter sample, is probably an early Ames substrain, eg, the one isolated in 1928. (If, however, the substrain was a later isolate, eg, 1980, that would prove that the letter anthrax was made after 1972.) Although Vollum was the main strain stockpiled by the US during WWII, the search undoubtedly continued for better strains. The US BW program and biodefense program apparently switched to the Ames reference strain because of its high virulence.
• Undoubtedly the confusion about Ames substrains could be cleared up by USAMRIID, but they have been evasive.
• The motive of the perpetrator was not necessarily to kill but to create public fear, thereby raising the profile of BW. He simply took advantage of Sept 11 to throw suspicion elsewhere. The letters warned of anthrax or the need to take antibiotics, making it possible for those who handled the letters to protect themselves; and it seems unlikely that the perpetrator would have anticipated that the rough treatment of mail in letter sorters etc, would force anthrax spores through the pores of the envelopes (which were taped to keep the anthrax inside) and infect postal workers.
• The choice of media as targets seems designed to ensure publicity about the threat of biological weapons. One can only speculate that the perpetrator may have wished to push the US government toward retaliatory action against some enemy, or to attract funding or recognition to some program with which he is associated.
• The US government has known for some time that the anthrax terrorism was an inside job. They may be reluctant to admit this. They also may not yet have adequate hard evidence to convict the perpetrator. In opposition to most of the countries of the world, the US turned down a Protocol to monitor compliance with the ban on biological weapons last July. Now we find that the US has been attacked by BW through its own laxity. At the Review Conference, the US delegation is proposing, as an alternative to monitoring compliance internationally, a set of national actions for other countries to take. These include regulating access to dangerous pathogens. Physician, heal thyself.

 
• Conclusions: A recent report by the GAO, and many recent statements by experts in the BW field, hold that terrorists are unlikely to be able to mount a major biological attack without substantial assistance from a government sponsor. The recent anthrax attack was a minor one but nonetheless we now see that it was perpetrated with the unwitting assistance of a sophisticated government program. It is reassuring to know that it was not perpetrated by a lone terrorist without such support. However it is not reassuring to know that a secret US program was the source of that support. Secret threat assessment activities are undermining the intent of the Biological Weapons Convention and encouraging BW proliferation in other countries, which in turn may support terrorist attacks on the US.