Ala. Code § 22-50-22
Neither the superintendent nor a physician of a state mental health facility or hospital shall be compelled to attend as a witness to testify as an expert in any case or on any question of insanity or psychological medicine in the state; provided, that he shall certify, in writing, within 10 days after the service of the summons, that his absence from the facility or hospital, in his best judgment, will interfere with his or her professional duties and the welfare of the patients under his care. But defendants in criminal cases and the state by the consent of the defendant and, in civil cases, either party may take the deposition of the superintendent or of any of the physicians as to all matters involving his or their expert opinion when such testimony is admissible.
Ala. Code § 22-50-22 (1975)