The FBI's investigation into the mailings, which killed five people and made 17 others ill, implicated Bruce Ivins, an Army microbiologist who killed himself in 2008. The FBI linked him to the mailing based on genetic evidence that the mailed spores were similar to the ones from Ivins' lab at Fort Detrick.
The review, conducted by the Government Accountability Office, was requested by Congress in 2010 and, the Times notes, echoes many of the findings from the 2011 inquiry conducted by the National Academy of Sciences. The GAO, though, had better access to FBI files, it adds.
The GAO found a number of flaws in the FBI's scientific process. As ScienceInsider notes, the FBI investigation lacked a framework to ensure standardized testing.
"As a result, each of the [four] contractors developed their tests differently, and one contractor did not conduct verification testing, a key step in determining whether a test will meet a user's requirements, such as for sensitivity or accuracy," the report says.
Additionally, the report notes that the investigation seemed to suffer from a lack of understanding of how bacteria naturally mutate over time and how that could influence testing. "Specifically, the significance of using such mutations as genetic markers for analyzing evidentiary samples to determine their origins is not clear," the report says. "This gap affects both the development of genetic tests targeting such mutations and statistical analyses of the results of their use on evidentiary samples."
Timothy Persons, the chief scientist at the GAO tells the New York Times that the FBI "needed better science and measurement in order to be more conclusive, It sounds nitpicky, but that's important in building up the scientific evidence for an important case."
The report does not cover the conclusions the FBI made when it closed this case in 2010.