In late January 2003, as Secretary of State Colin Powell prepared to argue the Bush administration's case against Iraq at the United Nations, veteran CIA officer Tyler Drumheller sat down with a classified draft of Powell's speech to look for errors. He found a whopper: a claim about mobile biological labs built by Iraq for germ warfare.
Drumheller instantly recognized the source, an Iraqi defector suspected of being mentally unstable and a liar. The CIA officer took his pen, he recounted in an interview, and crossed out the whole paragraph.
A few days later, the lines were back in the speech. Powell stood before the U.N. Security Council on Feb. 5 and said: "We have first-hand descriptions of biological weapons factories on wheels and on rails."