Health & Saf. Code, § 11712

(a) Proof of liability in an action brought under this division shall be shown by clear and convincing evidence. Except as otherwise provided in this division, other elements of the cause of action shall be shown by a preponderance of the evidence.

(b) (1) A person against whom recovery is sought who has a criminal conviction pursuant to state laws prohibiting the illegal sale of controlled substances or the Comprehensive Drug Abuse Prevention and Control Act of 1970 (Public Law 91-513, 84 Stats. 1236, codified at 21 U.S.C. Sec. 801 et seq.), is estopped from denying participation in the illegal market for controlled substances. Except as provided in paragraph (2), this subdivision does not affect the plaintiff’s burden of proving subparagraphs (A), (B), and (C) of paragraph (2) of subdivision (b) of Section 11705.

(2) Such a conviction is also prima facie evidence of the person’s participation in the marketing of a specified illegal controlled substance used by the individual user where that conviction was based upon the person’s marketing of that same type of illegal controlled substance.

(c) The absence of a criminal conviction of a person pursuant to subdivision (b) against whom recovery is sought does not bar an action against that person in an action pursuant to paragraph (1) of subdivision (b) of Section 11705, or Section 11706..