(a) If notice of intention to raise the insanity defense is filed under Article 46C.051, the court may, on its own motion or motion by the defendant, the defendant's counsel, or the attorney representing the state, appoint one or more disinterested experts to:
(1) examine the defendant with regard to the insanity defense; and
(2) testify as to the issue of insanity at any trial or hearing involving that issue.
(b) The court shall advise an expert appointed under this article of the facts and circumstances of the offense with which the defendant is charged and the elements of the insanity defense.