Four key prosecution witnesses defied subpoenas and failed to appear to testify at the trial of the Philippines' armed forces chief, Gen. Fabian C. Ver, and 25 others in the 1983 assassination of opposition leader Benigno S. Aquino Jr. Prosecution attorneys said they were having trouble finding six other important witnesses, who were not named. The four who defied subpoenas are all members of the family of the late Rolando Galman, the man identified by the military as Aquino's killer. They said they will not testify until all the defendants are in a civilian prison. Most of the accused servicemen are in the custody of their commanding officers.