as a result of mental disease or defect he lacks substantial capacity either to appreciate the criminality [wrongfiilness] of his conduct or to conform his conduct to the requirements of law.’ ” (People v. Drew (1978) 22 Cal.3d 333, 345 [149 Cal.Rptr. 275, 583 P.2d 1318].)
In June 1982, the electorate passed an initiative measure that, among other things, established the state’s first statutory definition of insanity: “In any criminal proceeding ... in which a plea of not guilty by reason of insanity is entered, this defense shall be found by the trier of fact only when the accused person proves by a preponderance of the evidence that he or she was incapable of knowing or understanding the nature and quality of his or her act and, of distinguishing right from wrong at the time of the commission of the offense.” (§ 25(b), italics added; see People v. Skinner, supra, 39 Cal.3d at p. 768.)
Despite the use of the conjunctive “and” instead of the disjunction “or” to connect the two prongs, we held in Skinner, supra, 39 Cal.3d at page 769, “that section 25(b) was intended to, and does, restore the M’Naghten test as it existed in this state before Drew,” and that “under that test there exist two distinct and independent bases upon which a verdict of not guilty by reason of insanity might be returned.”
As a result of Skinner, supra, 39 Cal.3d 765, defendant’s vagueness challenge to section 25(b) is nothing less than a challenge to the M’Naghten test itself as it existed for over a century in this state and even longer in other parts of the common law world. As we explain, that test passes constitutional muster.
Due process requires a “ ‘reasonable degree of certainty in legislation, especially in the criminal law ....’” (In re Newbern (1960) 53 Cal.2d 786, 792 [3 Cal.Rptr. 364, 350 P.2d 116], quoted in People v. Mirmirani (1981) 30 Cal.3d 375, 382 [178 Cal.Rptr. 792, 636 P.2d 1130].) Thus, a statute must be definite enough to provide (1) a standard of conduct for those whose activities are proscribed and (2) a standard for police enforcement and for ascertainment of guilt. (Burg v. Municipal Court (1983) 35 Cal.3d 257, 269 [198 Cal.Rptr. 145, 673 P.2d 732], and cases cited therein.) The second of these criteria is the more important (id. at p. 269, fn. 15, citing Kolender v. Lawson (1983) 461 U.S. 352 [75 L.Ed.2d 903, 103 S.Ct. 1855]; People v. Wooten (1985) 168 Cal.App.3d 168, 174 [214 Cal.Rptr. 36]), especially in this situation. A person does not become sane or insane while committing crimes in reliance upon a statutory definition.
The statute here is reasonably certain. “Many, probably most, statutes are ambiguous in some respects and instances invariably arise under which the