Secret Witness Set to Testify In Terror Trial
Trial in bombings of two American embassies in East Africa is to begin in Federal District Court in Manhattan and indications are that government's first witness will be an informer who worked for Saudi exile Osama bin Laden until 1996, when he agreed to cooperate with American authorities; government has been concealing identity of witness, convicted terrorist known only as CS-1 for almost 5 years (M)