California Code, Penal Code - PEN § 1054.5

(a) No order requiring discovery shall be made in criminal cases except as provided in this chapter. This chapter shall be the only means by which the defendant may compel the disclosure or production of information from prosecuting attorneys, law enforcement agencies which investigated or prepared the case against the defendant, or any other persons or agencies which the prosecuting attorney or investigating agency may have employed to assist them in performing their duties.

(b) Before a party may seek court enforcement of any of the disclosures required by this chapter, the party shall make an informal request of opposing counsel for the desired materials and information. If within 15 days the opposing counsel fails to provide the materials and information requested, the party may seek a court order. Upon a showing that a party has not complied with Section 1054.1 or 1054.3 and upon a showing that the moving party complied with the informal discovery procedure provided in this subdivision, a court may make any order necessary to enforce the provisions of this chapter, including, but not limited to, immediate disclosure, contempt proceedings, delaying or prohibiting the testimony of a witness or the presentation of real evidence, continuance of the matter, or any other lawful order. Further, the court may advise the jury of any failure or refusal to disclose and of any untimely disclosure.

(c) The court may prohibit the testimony of a witness pursuant to subdivision (b) only if all other sanctions have been exhausted. The court shall not dismiss a charge pursuant to subdivision (b) unless required to do so by the Constitution of the United States.