A subpoena (or ) is a writ issued by a court that commands the presence of a witness to testify, under a penalty for failure. Subpoenas are associated with common law legal systems. There are two common types of subpoena:1 subpoena ad testificandum orders a person to testify before the ordering authority or face punishment. 2 subpoena duces tecum orders a person to bring physical evidence before the ordering authority or face punishment. Etymology The term is from the Middle English suppena an… (More on Subpoena)