Holding that the failure to instruct on a lesser included offense in a noncapital case is, at most, an error of California law alone subject only to state standards of reversibility
Finding failure to instruct on heat of passion voluntary manslaughter harmless because among other things, "[o]nce the jury rejected defendant's claims of reasonable and imperfect self-defense, there was little if any independent evidence remaining to support his further claim that he killed in the heat of passion . . . or acted rashly or impulsively while under its influence for reasons unrelated to his perceived need for self-defense."
Finding that under circumstances in which defendant testified "the gun just went off," jury could have properly found "the death was the result of the failure to exercise proper care under the circumstances" and thus supported conviction for involuntary manslaughter
Concluding that "an intentional killing is reduced to voluntary manslaughter ... when the defendant acts upon a sudden quarrel or heat of passion on sufficient provocation"