What is a trial court duty to instruct a defendant on a particular defense?

"In criminal cases, even in the absence of a request, a trial court must instruct on general principles of law relevant to the issues raised by the evidence and necessary for the jury's understanding of the case. [Citation.] 'A trial court's duty to instruct, sua sponte, on particular defenses arises " 'only if it appears that the defendant is relying on such a defense, or if there is substantial evidence supportive of such a defense and the defense is not inconsistent with the defendant's theory of the case.' " ' " (People v. Martinez (2010) 47 Cal.4th 911, 953.) " 'But " 'when a defendant presents evidence to

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