A deposition subpoena requires a non-party to testify and/or produce documents during the informal pre-trial discovery phase of the lawsuit. A deposition will take place outside the courtroom, usually in an attorney's office. In contrast, a subpoena to testify or subpoena duces tecum (to produce documents) requires a non-party to testify and/or produce documents in a formal court hearing. A deposition subpoena must be accompanied by a Notice of Deposition to be valid. The Notice of Deposition will state the time and date of the deposition. The deponent must also be given advance notice of the deposition date.