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Alice Gast: evidence not conclusive for 2001 anthrax mailings

A National Research Council says it isn’t possible to reach a definitive conclusion about the origin of deadly anthrax spores, based on the scientific evidence alone.

The National Research Council has released a study on the science used in the investigation of the 2001 anthrax mailings that killed five people and infected 17 in the U.S. in 2001. The study concludes that it’s not possible to reach a definitive conclusion – based on the science alone – about the origin of the deadly anthrax spores used in the mailings.

Anthrax letters. Image Credit: wikimedia

Soon after the 9-11 terrorist attack in the U.S. in 2001, letters containing Bacillus anthracis were mailed to media offices and to two U.S. senators. Subsequently, a key suspect in the mailings was identified – a U.S. Army anthrax researcher, Bruce Ivins. He committed suicide in 2008, before he was tried.

The National Research Council study, released in early 2011, examined the science used in the investigation by the FBI. EarthSky spoke with Dr. Alice Gast, a chemical engineer and chair of a committee for the National Research Council. The committee scrutinized evidence of the positive link made between strains of the anthrax in the letters and the the anthrax in Dr. Ivins’s lab. Gast told EarthSky:

The overarching finding is that it’s not possible to reach a definitive conclusion about the origin of the B. anthracis in the mailings based on the scientific evidence alone.

Bruce Ivans at an award ceremony in 2003. Image Credit: Wikipedia)

In some sense it raises the fact that you can’t make an absolute link between the samples, because of the fact that B. anthracis readily forms various mutations of this type. There are other scenarios that you could think of where those mutants would develop through their own evolutionary processes.

B. anthracis is the anthrax strain in the letters. Dr. Gast also said:

What turned out to be the most important part of this particular study was the observation fairly early on by a scientist and a technician that the material in the letters would form colonies that had different shapes. They’re called morphological variants or morphological mutations, morpho-types as we call them.

In other words, even though the anthrax spores on the letters matched samples from the suspect’s lab, that match could just have been a coincidence or a mutation of the anthrax strain, and not necessarily proof that one came from the other.

Dr. Gast added that the years-long investigation did yield positive results by coordinating oversight between scientists and law enforcement, which might prove helpful to the nation in the event of a future anthrax attack. She said that a lot of sciences came together in this investigation, and that there were physical and chemical analysis as well as the micro, biological, and genetic analysis of the letters. She said:

One of the key challenges that we faced, and the FBI faced, is how to take the newest science and the newest technologies and validate it for use in these imperfect experiments, if you will, that you get from a crime scene or from a scenario where you certainly weren’t devising a scientific research project. You were dealing with the samples you had. Validation and the ability to trust the latest in technology is really important. And so the speed with which we can go from a new technology to a new technology validated for forensics and these type of investigations is important.

Today, we have available high-throughput genome sequencing, and there are a lot of new technologies that would help in a scenario like this, if it were to happen again.

Gast said that most important thing she’d like people today to know about the scientific review of evidence from the case of the 2001 anthrax mailings is that science is not absolute. She added:

And when it comes into a courtroom, I fear that it’s sometimes put on a higher pedestal or treated as an absolute. And there are uncertainties in science, just as there are uncertainties in other pieces of evidence. I think communicating clear expectations of what one can get from these type of investigations is very important during the process and when presenting the results of an investigation. But the public also has to understand that just because it may sound high-tech to them, it doesn’t mean that it’s ironclad.

So the origin of the 2001 anthrax mailings – which killed five people and infected 17 in the U.S. in 2001 – remains unclear, according to a National Research Council study released in 2011. Although anthrax spores in the letters matched samples from a key suspect’s lab, that match could just have been a coincidence or a mutation of the anthrax strain, and not necessarily proof one came from the other, according to the report.

Jorge Salazar

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