The court on all proper occasions shall instruct the jury as to which party bears the burden of proof on each issue and as to whether that burden requires that a party raise a reasonable doubt concerning the existence or nonexistence of a fact or that he establish the existence or nonexistence of a fact by a preponderance of the evidence, by clear and convincing proof, or by proof beyond a reasonable doubt.
(Enacted by Stats. 1965, Ch. 299.)