KARLSRUHE, Germany - The only person in the world convicted in the Sept. 11 attacks won a retrial Thursday after an appeals court faulted Washington for refusing to allow testimony from a key al-Qaida captive. The Federal Criminal Court overturned the conviction of Mounir el Motassadeq, a Moroccan, leaving German prosecutors with little to show for their efforts to pursue suspects who may have belonged to the Hamburg cell that included three of the suicide hijackers. A month ago, el Motassadeq's friend Abdelghani Mzoudi was acquitted of identical charges of giving logistical aid to the cell. Relatives of Sept. 11...