An Illinois Subpoena is a court order issued in the state of Illinois that requires a witness or entity to appear at a hearing or trial or to provide documents or other evidence in a legal proceeding. There are two types of Illinois Subpoenas: a Subpoena Ducks Cecum (SET) and a Subpoena Ad Testificandum (SAT). A Subpoena Ducks Cecum (SET) is a court order that requires a witness or entity to appear and produce evidence, such as documents or other items. A Subpoena Ad Testificandum (SAT) is a court order that requires a witness or entity to appear and testify in a legal proceeding.