The scientific evidence that the US Federal Bureau of Investigation (FBI) relied upon to investigate the October 2001 anthrax attacks – and ultimately identify the culprit after his suicide – was deeply flawed, according to a new report from the congressional Government Accountability Office (GAO).

The GAO found that the FBI lacked a comprehensive approach or framework to standardize the genetic testing used to track down the culprit. It also found that each of the FBI’s four contractors developed different tests and there was no statistical confidence for interpreting the results.

These genetic analyses were used to link the material found in the anthrax-laden letters to the laboratory of Bruce Ivins, a senior biodefence researcher at the US Army Medical Research Institute of Infectious Diseases. In February 2010, the FBI formally concluded that Ivins, who committed suicide in 2008, was solely responsible for the attacks.

‘The lack of an understanding of how bacteria change (mutate) in their natural environment and in a laboratory is a key scientific gap that remains and could affect testing conducted in future incidents,’ the GAO concluded. Specifically, the office said the significance of using such mutations as genetic markers to analyse samples to determine their origins remains unclear.

The GAO noted that the Department of Homeland Security is currently funding research on mutation in bacteria and genome sequencing methods. However, this research may not be complete for several years.

The investigation was undertaken partly because of questions raised by a National Academies study released in 2011, which determined that the FBI’s scientific data did not rule out other possible sources of the weaponised anthrax spores in the letters.

The GAO also found that one of the four genetic tests the FBI used on the anthrax samples had a 43% false negative rate. ‘That just really dropped my jaw, and it should be very embarrassing to the FBI that they still relied on that,’ says Jim White, a now retired molecular biologist with expertise in fermentation technology and microbial growth. Two of the three other genetic tests that the FBI relied on had false negative rates in the 20% range.

The FBI issued a response saying it has ‘complete confidence’ in its scientific results. The agency said the genetic tests it used were ‘well validated’, and that it has reviewed the results of all scientific analysis conducted during the course of the investigation and is satisfied by its quality. The FBI further noted that the scientific results alone were not the sole basis for concluding that Ivins committed the attacks.

But White and others argue that the information and questions that have surfaced in recent years warrant reopening the case.

Retiring congressman Rush Holt, whose New Jersey district was a target of the anthrax letters, requested the GAO study. Holt, who is set to be the next president of the American Association for the Advancement of Science, said the GAO findings confirm that the FBI’s conclusions about the anthrax attacks are not definitive. Holt is quoted as saying that the US needs a ‘comprehensive, independent review’ of the FBI investigation to ensure that lessons have been learned.

This article is reproduced with permission from Chemistry World. The article was first published on December 24, 2014.