Sunday, August 10, 2008

Questions about the Bruce Ivins Anthrax Case

Dr. Gerry Andrews, a professor of microbiology, raises some interesting questions about the evidence against his former colleague, Dr. Bruce Ivins, the suspected "anthrax killer" who recently committed suicide. See Gerry Andrews, "Open Questions on a Closed Case" (Op-Ed), NYTimes Online (August 9, 2008). Of particular interest to me are several questions that Dr. Andrews raises about the scientific evidence in the case.

The US attorney supervising the investigation and other government agents spoke about the "match" between the anthrax that killed the five victims and the anthrax that had been in Ivins' possession. One government agent -- I believe it was the the US attorney who held the news conference about the impending closing of the case -- even said that the government had located the "murder weapon," the flask containing the lethal anthrax that, it was said, killed the five victims.

Although I have no reason to doubt that the federal government has (finally) fingered the right (dead) man, one must always be suspicious when there is talk about a "match." The word "match" implies evidence that uniquely identifies the thing (or, worse yet) person who left some trace at the crime scene. Dr. Andrews points out several circumstances and considerations that raise questions about the government hypothesis that the scientific evidence in the case points uniquely to Bruce Ivins as the culprit. He makes his point this way:

As a scientist, ... I feel compelled to comment on what should have been the Federal Bureau of Investigation’s strongest link between Dr. Ivins and the terrible crime — deadly anthrax spores. In the summary of its findings, the F.B.I. states that investigators used four different genetic techniques to match the anthrax-laced attack letters to a unique DNA footprint of a single anthrax spore preparation in one flask that had been in Dr. Ivins’s custody.

Sounds reasonable. Yet the investigators present no details on the scientific methods they used to make this match or how they employed them. That’s a problem, because without such detail it is hard to tell if they specifically ruled out a similar match between the anthrax in the letters and anthrax preparations with the same DNA footprint kept at a number of other labs around the country.

For good measure, Dr. Andrews points out how "non-scientific" questions about the custody of the "murder weapon" raise additional doubts about the strength of the scientific evidence against Ivins. Andrews begins by noting that "Dr. Ivins was an investigator in the case before he was a suspect. After the anthrax attack, Dr. Ivins himself worked directly with the evidence. The F.B.I. asked Dr. Ivins to help them with the forensics in the case by analyzing the contents of suspicious letters. And he did so for years, until the authorities began to suspect that the anthrax spores used in the mailings might have originated from his lab." Dr. Andrews argues that the lab at which Ivins worked did not have the capacity to produce the "refined weapons-grade anthrax" that had been used to kill the five victims. Dr. Andrews then adds:
But even leaving that aside, there are important questions left unanswered. First, isn’t it possible that the manipulation of the contents of the anthrax letters in Dr. Ivins’s laboratory might have contaminated the work environment enough to potentially jeopardize the integrity of subsequent samples taken from the lab? Might that perhaps explain why the anthrax powder used in the attacks was later found to have the same DNA footprint as the other anthrax preparations in Dr. Ivins’s lab? At the very least, wouldn’t this call his guilt into doubt?
These are the sorts of questions -- e.g., the degree to which the DNA of the physical sample found at the scene of the crime together with the DNA of a specimen found elsewhere is a distinctive identifier of the physical source of the crime scene specimen, the possibility of contamination of the physical evidence found either at the scene of the crime or elsewhere, the availability of the possible instrumentality of the crime (in this case the "murder weapon") to persons other than a specific suspect, -- these are the sorts of questions that have emerged in innumerable "humdrum" murder and rape cases. Despite the new scientific techniques that are said to have been developed during the investigation of the anthrax case, these sorts of issues are pertinent in the Ivins anthrax case as well in humdrum murder and rape cases. We should avoid being unduly dazzled by novel scientific methods or technology. We must always keep in mind what sorts of questions a powerful scientific method can answer and what sorts of questions it cannot answer.

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