Department of Justice and FBI's handling of the investigation. The FBI formally closed its investigation on February 19, 2010.

In 2008, the FBI requested a review of the scientific methods used in their investigation from the National Academy of Sciences, which released their findings in the 2011 report Review of the Scientific Approaches Used During the FBI's Investigation of the 2001 Anthrax Letters. The report cast doubt on the government's conclusion that Ivins was the perpetrator, finding that the type of anthrax used in the letters