What is the legal test for heat of passion in a murder case?

offense arises if there is substantial evidence the defendant is guilty of the lesser offense, but not the charged offense. [Citation.] This standard requires instructions on a lesser included offense whenever '"a jury composed of reasonable [persons] could . . . conclude[]"' that the lesser, but not the greater, offense was committed. [Citation.] In deciding whether evidence is 'substantial' in this context, a court determines only its bare legal sufficiency, not its weight." (Id. at p. 177; in accord, People v. Moye (2009) 47 Cal.4th 537, 556.)

Murder is the unlawful killing of a human being with malice aforethought. ( 187, subd. (a).) A murder "may be reduced to voluntary manslaughter if the victim engaged in provocative conduct that would cause an ordinary person with an average disposition to act rashly or without due deliberation and reflection." (People v. Booker (2011) 51 Cal.4th 141, 183, fn. 23; People v. Enraca (2012) 53 Cal.4th 735, 759.)

"Heat of passion has both objective and subjective components. Objectively, the victim's conduct must have been sufficiently provocative to cause an ordinary person of average disposition to act rashly or without due deliberation and reflection." (People v. Enraca, supra, 53 Cal.4th at p. 759.) "Subjectively, 'the accused must be shown to have killed while under "the actual influence of a strong passion" induced by such provocation. [Citation.] "Heat of passion arises when 'at the time of the killing, the reason of the accused was obscured or disturbed by passion to such an extent as would cause the ordinarily reasonable person of average disposition to act rashly and without deliberation and reflection, and from such passion rather than from judgment.'"'" (Ibid.)

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