Title 5 of the U.S. Code authorizes OSC to issue subpoenas for documents or the attendance and testimony of witnesses. During an investigation, OSC may require employees and others to testify under oath, sign written statements, or respond formally to written questions.
Federal employees are also required to provide to OSC any information, testimony, documents, and material, the disclosure of which is not otherwise prohibited by law or regulation, in investigations of matters under civil service law, rule, or regulation. The same rule requires federal agencies to make employees available to testify, on official time, and to provide pertinent records to OSC.
Ref: 5 U.S.C. § 1212(b); 5 C.F.R. § 5.4