Submission + - Faulty FBI Bullet Science Exposed (washingtonpost.com)
eldavojohn writes: "It's something that dates back to President Kennedy's assassination — bullet lead analysis. This technique is built upon the premise that every batch of bullets has its own impurities and chemical makeup that make it possible to distinguish between two bullets from different batches and link fired bullets to unused bullets in someone's possession. Something fishy was up two years ago when the FBI stopped using this technique and instead said it still supports the science behind it. Now the Washington Post & 60 Minutes are uncovering what could be hundreds of wrongly imprisoned people. The National Academy of Sciences denounced the 'science' of bullet lead analysis in 2004 with this core criticism: 'In 1996, the bureau switched to a new method called "inductively coupled plasma optical emission spectroscopy," in which scientists identified and measured seven trace elements in the bullets, adding the elements bismuth, cadmium, tin and silver. The goal was to increase the precision of the tests. But at the same time that it was measuring more elements, the FBI doubled the margin of error for declaring matches. "Not enough suspects were being caught in the new net using seven elements, so they chose to use a bigger net," said Clifford Spiegelman, a statistician at Texas A&M University who reviewed the FBI's statistical methods for the science academy.'"
