A Louisiana Subpoena to Testify at a Deposition in a Criminal Case is a legal document issued by a court or prosecuting attorney that requires a witness to appear and give testimony in a criminal case. This type of subpoena is generally served on the witness in person, and requires compliance with the instructions given by the court. There are two types of Louisiana Subpoena to Testify at a Deposition in a Criminal Case: an Ad Testificandum and a Ducks Cecum. An Ad Testificandum requires the witness to appear and testify at the deposition. A Ducks Cecum requires the witness to bring documents or other physical evidence to the deposition.