Would a Scan or a Pat-Down Have Detected the Underwear Bomb?

A story in the London Independent suggests that neither a millimeter-wave body scan nor a pat-down would have detected the bomb in Umar Farouk Abdulmutallab's underwear. According to Ben Wallace, a Conservative M.P. who helped develop the scanners for airport use, they are good at revealing dense objects such as guns, knives, and C4 plastic explosive but miss low-density material such as the three ounces of PETN powder Abdulmutallab carried. And since American screeners are "forbidden from frisking sensitive areas," a security analyst tells The Independent, it's unlikely they would have felt the explosive in Abdulmutallab's crotch even if they had patted him down. If the experts cited by the Independent are right, responding to Abdulmuttalab's attempted bombing with more pat-downs and more scans, as the U.S., the U.K., and the Netherlands have, is a non sequitur.