Cal. Health & Safety Code § 24175

(a) Except as otherwise provided in this section, no person shall be subjected to any medical experiment unless the informed consent of such person is obtained.
(b) If a person is under a conservatorship of the person or of the person and estate, pursuant to Division 4 (commencing with Section 1400) of the Probate Code, informed consent for a medical experiment involving such person shall be obtained:
1. (1) As provided in Section 2354 of the Probate Code if the person has not been adjudicated to lack the capacity to give informed consent for medical treatment.
2. (2) As provided in Section 2355 of the Probate Code if the person has been adjudicated to lack the capacity to give informed consent for medical treatment.
(c) If an adult person is gravely disabled, as defined in subdivision (h) of Section 5008 of the Welfare and Institutions Code, and is under a conservatorship of the person or of the person and estate, pursuant to Chapter 3 (commencing with Section 5350) of Part 1 of Division 5 of the Welfare and Institutions Code, informed consent for a medical experiment involving such person shall be obtained from such person, unless the conservator of such person has the right to consent to medical treatment on behalf of the conservatee, pursuant to subdivisions (c) and (d) of Section 5357 and Section 5358 of the Welfare and Institutions Code.
(d) If an adult person is developmentally disabled, as defined in subdivision (a) of Section 4512 of the Welfare and Institutions Code, and has no conservator and is mentally incapable of giving informed consent, informed consent shall be obtained for a medical experiment involving such person, pursuant to subdivision (c) of Section 4655 of the Welfare and Institutions Code.
(e) Informed consent given by a person other than the human subject pursuant to subdivisions (b) through (d), inclusive, of this section shall only be for medical experiments related to maintaining or improving the health of the human subject or related to obtaining information about a pathological condition of the human subject.