California Landmark Cases on the Insanity Defense

The defense of insanity "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 or of distinguishing right from wrong at the time of the commission of the offense." ( 25, subd. (b); People v. Skinner (1985) 39 Cal.3d 765.) To be incapable of "distinguishing right from wrong," the defendant need only be incapable of distinguishing moral right from moral wrong. (People v. Skinner, supra, at pp. 777-784.) Drug use or intoxication, however, offers no support for an insanity defense. (People v. Henning (2009) 178 Cal.App.4th 388, 401.) "Although unanimity of expert opinion that the defendant was insane carries persuasive value , a jury, under certain circumstances, can properly reject such opinions." (People v. Coogler (1969) 71 Cal.2d 153, 166.) For example, a jury may reject expert opinion when it is based on a defendant's self-serving descriptions of his thoughts and feelings. (Id. at pp. 166-168.) "'"However impressive this seeming unanimity of expert opinion may at first appear ... our inquiry on this just as on other factual issues is necessarily limited at the appellate level to a determination whether there is substantial evidence in the record to support the jury's verdict of sanity .... It is only in the rare case when 'the evidence is uncontradicted and entirely to the effect that the accused is insane' that a unanimity of expert testimony could authorize upsetting a ... finding to the contrary." Indeed the Supreme Court has frequently upheld on appeal verdicts which find a defendant to be sane in the face of contrary unanimous expert opinion. ' " (People v. Skinner (1986) 185 Cal.App.3d 1050, 1059-1060.) The Court held that we review a jury's determination of sanity under the substantial evidence test. (People v. Belcher (1969) 269 Cal.App.2d 215, 220.) The Court "must consider the whole record, view the evidence in the light most favorable to the judgment, presume every fact the trier of fact could reasonably deduce from the evidence, and defer to the trier of fact's determination of the weight and credibility of the evidence." (People v. Padilla (2002) 98 Cal.App.4th 127, 134-135.) "Because the burden was on the defense to show by a preponderance of the evidence that the defendant was insane, before we can overturn the jury's finding to the contrary, we must find as a matter of law that the jury could not reasonably reject the evidence of insanity. " (People v. Skinner, supra, 185 Cal.App.3d at p. 1059.)