January 15, 2006 -- WASHINGTON — U.S. officials are still holding out hope they killed Ayman al-Zawahiri, Osama bin Laden's top lieutenant, in an airstrike in Pakistan. Sources say American officials are anxiously awaiting DNA test results to determine if the Friday strike killed the Egyptian doctor, al Qaeda's second-in-command. Tissue samples taken from people killed in the strike are being flown to Quantico, Va., where the FBI will test them, sources say. [snip] But privately, sources say the strike was based on strong intelligence that Zawahiri would be among the guests at a dinner party there, and that he...