California Code, Government Code - GOV § 18673

If a witness does not reside within 100 miles of the place where the hearing or investigation is held, is out of the state or is too infirm to attend the hearing or investigation, any party thereto at his or her own expense may cause his or her deposition to be taken.

If a “statewide” subpoena has been issued and served on a witness, his or her deposition shall not be used as evidence, but he or she shall be personally present at any hearing or investigation at which he or she is a witness. If the presence of any other witness cannot be procured at the time of the hearing or investigation, the deposition of that witness may be used in evidence by either party or the board.