“California law requires a trial court, sua sponte, to instruct fully on all lesser necessarily included offenses supported by the evidence.” (People v. Breverman (1998) 19 Cal.4th 142, 148–149.) The requirement applies when there is substantial evidence that the defendant committed the lesser offense instead of the greater offense. (Id. at pp. 162, 177.)
“In deciding whether evidence is ‘substantial’ in this context, a court determines only its bare legal sufficiency, not its weight.” (Breverman, supra, 19 Cal.4th at p. 177.) Thus, “courts should not evaluate the credibility of witnesses, a task for the jury” (id. at p. 162), and uncertainty about whether the evidence is sufficient to warrant instructions should be resolved in favor of the accused. (People v. Tufunga (1999) 21 Cal.4th 935, 944; see also People v. Vasquez (2018) 30 Cal. App. 5th 786, 792.)
“Even evidence that is unconvincing or subject to justifiable suspicion may constitute substantial evidence and may trigger the lesser-included-offense requirement.” (Ibid; see also People v. Turner (1990) 50 Cal.3d 668, 690.)
The refusal to instruct on a lesser included offense may also violate the federal constitution’s requirement that the courts afford every criminal defendant “‘a meaningful opportunity to present a complete defense.’” (Crane v. Kentucky (1986) 476 U.S. 683, 690; see People v. Rogers (2006) 39 Cal.4th 826, 868, fn. 16.) As part of this right, a defendant is “‘entitled to adequate instructions on the defense theory of the case’ if supported by the law and evidence [citation] and ‘“has a constitutional right to have the jury determine every material issue presented by the evidence …”’ [citation].” (People v. Eid (2010) 187 Cal.App.4th 859, 879; see People v. Cash (2002) 28 Cal.4th 703, 736 [“Defendants have a constitutional right to have the jury determine every material issue presented by the evidence, and a trial court’s failure to instruct on lesser included offenses denies them that right.”]; see also People v. Vasquez, supra, 30 Cal. App. at 793.)
