California Code, Probate Code - PROB § 4714

A surrogate, including a person acting as a surrogate, shall make a health care decision in accordance with the patient's individual health care instructions, if any, and other wishes to the extent known to the surrogate. Otherwise, the surrogate shall make the decision in accordance with the surrogate's determination of the patient's best interest. In determining the patient's best interest, the surrogate shall consider the patient's personal values to the extent known to the surrogate.