Legal Question in Family Law in California

If no documents are required to be produced along with the witness, there is no specific time limit. You can subpoena a witness during trial. What you risk the more you wait, however, is that if the witness doesn't show, the court will decline to hold them in contempt, and will not deem them "unavailable" for purposes of introducing alternative evidence to their testimony. If there are documents required, then there are specific deadlines, but they depend on the nature of the documents and the witness, and are too complicated to just list them all here.