Cal. PROB § 3201

(a) A petition may be filed to determine that a patient has the capacity to make a health care decision concerning an existing or continuing condition. (b) A petition may be filed to determine that a patient lacks the capacity to make a health care decision concerning specified treatment for an existing or continuing condition, and further for an order authorizing a designated person to make a health care decision on behalf of the patient. (c) One proceeding may be brought under this part under both subdivisions (a) and (b).