Imperfect Self-Defense in New Mexico: An Introduction
Unfortunately for her client, the short answer is: "like the facts of your case"--the defendant acted sincerely in self-defense but did so unreasonably, either because she was unreasonable in her perception of imminent threat (i.e., waiting until the threat is asleep, mistaking a baseball bat for a gun), or unreasonable in her reaction such that she uses disproportionate force (i.e., bringing a carpet-cutter to a slapping match).
Imperfect self-defense creates a lesser-included offense, not acquittal. It functions to remove or mitigate the intention element of the crime, dropping the crime by a degree. It most often provides a "third option" between guilt as charged and acquittal based on self-defense. Because of this splitting-of-the-baby, it is sometimes considered but strategically waived by counsel seeking an all-or-nothing (murder or acquittal) choice for the jury.
In New Mexico the defense of imperfect self-defense requires some specially-drafted jury instructions that include the specific facts of the case as per the defense theory. The great thing about imperfect self-defense, like self-defense, in New Mexico is that by factually raising it as a defense, the burden shifts to the government to prove the act was not done in imperfect self-defense beyond a reasonable doubt. If the jury retains a doubt as to whether the doctrine of imperfect self-defense has been met, it must “step down” to the next lower degree of crime. So, if there is doubt about whether she was sincerely thinking self-defense, even if all the jury agrees her actions were unreasonable, then she can't be found guilty of the crime as charged (and may be guilty of a lesser included offense like voluntary manslaughter). In a hypothetical case charging aggravated battery DV with great bodily harm, the relevant lesser-included offense could be simple battery or even disorderly conduct. In theory, if we are low enough on the hierarchy of crimes, the charged crime should step down to a civil law tort.
Okay that's pretty geeky. But the point is, imperfect self-defense is a defense often available in a case charging violence or homicide, especially those defended on a self-defense theory. Many a lawyer has carefully considered the consequences of an imperfect self-defense defense and, consulting with her client, decided as a matter of strategy to go all-or-nothing and abandon this defense. Many a plea offer looks much different when laid out beside the possibility of a lesser-included offense based on imperfect self-defense. The defense is worth fleshing out, and discussing deliberately, before being discarded. Without knowing this middle option much less counseling the client about it, how can a lawyer counsel her client on any plea offers effectively? How could she counsel her client to go "all or nothing" without laying out the third option that could be placed before the jury?
Once the jury is deliberating on the choice between guilt and self-defense, and it sends out questions about what it means when they think she over-did the violence in response to the threat, the time is way too late to learn for the first time about the law of imperfect self-defense.