Here's a mildly reassuring fact from today's AAAS news briefing on nuclear forensics: There are no known cases of a finished nuclear weapon being stolen or sold on the black market. But raw nuclear materials are a different story. In the past fifteen years, more than 1,300 cases of nuclear trafficking have been registered. Anita Nilsson of the International Atomic Energy Agency, a member of today's panel, said that most of these cases were "innocent," but some are anything but. The 400 grams of weapons-ready plutonium seized at the Munich airport in 1994?