What if you use deadly force because the attacker is about to kill you and you hate him?

Are you guilty of murder, because you didn't act based on your "fears alone," but based on your reasonable fears plus some other motive? The conventional answer is no: The LaFave treatise, for instance, expressly says that if a defender "acts in proper self-defense, he does not lose the defense because he acts with some less admirable motive in addition to that of defending himself, as where he enjoys using force upon his adversary because he hates him." The comment to Model Penal Code § 3.04, likewise states that self-defense "does not demand that [the belief of necessity of defensive action] be the sole motive of [the defendant's] action," because "an inquiry into dominant and secondary purposes would inevitably be far too complex." See State v. King (Ariz. 2010).

But in California (and apparently Idaho), it appears that you would be guilty of murder. California, like all states, allows people to use deadly force to resist an attempt to kill, inflict serious bodily injury, rape, or commit some other very serious crimes. But Cal. Penal Code § 198 provides that,

the circumstances must be sufficient to excite the fears of a reasonable person, and the party killing must have acted under the influence of such fears alone.

California Jury Instructions-Criminal No. 5.12 echoes this:

To justify taking the life of another in self-defense, the circumstances must be such as would excite the fears of a reasonable person placed in a similar position, and the party killing must act under the influence of those fears alone.

[UPDATE: The more recent Judicial Council Of California Criminal Jury Instruction No. 505 likewise says (emphasis added), "Defendant's belief must have been reasonable and (he/she) must have acted only because of that belief."] And People v. Trevino (Cal. App. 1988) interprets the statute this way (though note that the jury will generally see the pattern jury instructions, not the Trevino language) (emphasis added):

[A]n instruction which states that the party killing must act under the influence of such fears alone, is a correct statement of the law.

In so holding, we do not mean to imply that a person who feels anger or even hatred toward the person killed, may never justifiably use deadly force in self-defense. For example, it is settled that a person who has sought combat may decline further struggle and, if he really and in good faith does so before the killing, the killing may be justified on the same grounds as if that person had not originally been the aggressor. Furthermore, if a victim of a simple assault engages in a sudden and deadly counterassault, the original aggressor need not attempt to withdraw, and may reasonably use necessary force in self-defense.)

In such situations, as in others, it would be unreasonable to require an absence of any feeling other than fear, before the homicide could be considered justifiable. Such a requirement is not a part of the law, nor is it a part of CALJIC No. 5.12. Instead, the law requires that the party killing act out of fear alone. Thus, once the initial aggressor attempts in good faith to decline further struggle and communicates this to his opponent, or once the initial victim overreacts and responds with deadly force, the party killing may justifiably use deadly force in self-defense as long as the use of such force is motivated only by a reasonable fear and the belief that it is necessary to prevent his death or great bodily injury. The party killing is not precluded from feeling anger or other emotions save and except fear; however, those other emotions cannot be causal factors in his decision to use deadly force. If they are, the homicide cannot be justified on a theory of self-defense. But if the only causation of the killing was the reasonable fear that there was imminent danger of death or great bodily injury, then the use of deadly force in self-defense is proper, regardless of what other emotions the party who kills may have been feeling but not acting upon.

CALJIC No. 5.12 properly instructs the jury that the party killing must have acted under the influence of reasonable fears alone. It does not eliminate a feeling of anger or any other emotion so long as that emotion was not part of the cause of the use of deadly force. It is, therefore, a correct statement of the law of self-defense. In the case at bench, Trevino could have requested additional instructions with regard to his feeling anger toward Blanton as well as fear, or with regard to a situation where anger and fear were both causal factors. He did not do so. Nor did he argue to the jury the presence of such dual motivation or feeling. Under such circumstances, his argument on appeal must fail.

At the very least, this puts defendants in a difficult position where they feel both reasonable fear of death or serious bodily injury and hatred toward the attacker or a desire for revenge—quite a common scenario, I suspect, since if someone is the sort of person who's likely to violently attack you, he's also probably done some things that lead you to hate him. In such a situation, a jury might conclude (as per instruction 5.12) that the mix of motivations strips the defendant of his right to use deadly force in self-defense, since the defendant isn't acting on his "fears alone."

But beyond this, what of a situation where the defendant admits that she wouldn't have used deadly force because of reasonable fear of serious bodily injury alone, but also had another motivation? Say a woman is on trial for killing her abusive boyfriend. He had severely injured her or raped her before, and she had not used deadly force to defend herself then, even though she would have had the legal right to do so.

She confided to a friend after the killing that she likely wouldn't have defended herself with deadly force this time, either, had circumstances been as they had been before. But this time, something else has been added—for instance, he has admitted to abusing her daughter, or to cheating on her, or whatever else. Now when he was about to severely injure or rape her again, she stabbed him.

Is she acting based on "circumstances … be such as would excite the fears of a reasonable person placed in a similar position" that she would be severely injured or raped? Yes. But is she "act[ing] under the influence of those fears alone"? No: By her own admission, those fears alone had not led her to use deadly force to defend herself before, and wouldn't have led her to use deadly force in this situation, either. The desire for revenge against the boyfriend, or her feeling of betrayal, is a but-for cause of the killing, though of course the reasonable fear of serious bodily injury or rape is a but-for cause as well.

Under California law, it appears that the woman would be guilty of murder, despite the fact that she was defending herself against attack, because she also had another motive (revenge or hatred). That can't be right, I think. But that seems to be California law.