An Oklahoma Subpoena To Testify At a Deposition Civil is a legal document issued by a court in Oklahoma that requires a person to appear in court and testify at a deposition. This type of subpoena is used to compel a witness to appear before a court to provide testimony related to a civil case. There are two types of Oklahoma Subpoena To Testify At a Deposition Civil: a Subpoena Ducks Cecum and a Subpoena Ad Testificandum. A Subpoena Ducks Cecum requires the witness to bring documents, records, or other materials relevant to the case. A Subpoena Ad Testificandum requires the witness to appear in court and testify about matters related to the case.