What is the test for instructing a sua sponte on a self-defense defense?

"A trial court is required to instruct sua sponte on any defense, including self-defense, only when there is substantial evidence supporting the defense, and the defendant is either relying on the defense or the defense is not inconsistent with the defendant's theory of the case. [Citation.]" (People v. Villanueva (2008) 169

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Cal.App.4th 41, 49.) "In determining whether substantial evidence supports a defense, the trial court must leave issues of witness credibility to the jury. [Citation.]" (Ibid.) On review, we independently determine whether substantial evidence existed to support the defense. (People v. Shelmire (2005) 130 Cal.App.4th 1044, 1055.)