Because of the diligence, cooperation, and facilities of Federal investigative agencies, it was unnecessary for the Commission to employ investigators other than the members of the Commission’s legal staff. The Commission recognized, however, that special measures were required whenever the facts or rumors called for an appraisal of the acts of the agencies themselves. The staff reviewed in detail the actions of several Federal agencies, particularly the Federal Bureau of Investigation, the Secret Service, the Central Intelligence Agency, and the Department of State. Initially the Commission requested the agencies to furnish all their reports relating to the assassination and their relationships with Oswald or Ruby. On the basis of these reports, the Commission submitted specific questions to the agency involved. Members of the staff followed up the answers by reviewing the relevant files of each agency for additional information. In some instances, members of the Commission also reviewed the files in person. Finally, the responsible officials of these agencies were called to testify under oath. Dean Rusk, Secretary of State; C. Douglas Dillon, Secretary of the Treasury; John A. McCone, Director of the Central Intelligence Agency; J. Edgar Hoover, Director of the Federal Bureau of Investigation; and James J. Rowley, Chief of the Secret Service, appeared as witnesses and testified fully regarding their agencies’ participation in the matters under scrutiny by the Commission. COMMISSION HEARINGS In addition to the information resulting from these investigations, the Commission has relied primarily on the facts disclosed by the sworn testimony of the principal witnesses to the assassination and related events. Beginning on February 3, 1964, the Commission and its staff has taken the testimony of 552 witnesses. Of this number, 94 appeared before members of the Commission; 395 were questioned by members of the Commission’s legal staff; 61 supplied sworn affidavits; and 2 gave statements.[F-4] Under Commission procedures, all witnesses were advised that they had the right to the presence and the advice of their lawyer during the interrogation, with the corollary rights to raise objections to any questions asked, to make any clarifying statement on the record after the interrogation, and to purchase a copy of their testimony.[F-5]