Introduction

Imperfect Self-Defense and Manslaughter

Introduction

A person kills another intentionally because he sincerely believes deadly force is the only way to survive, and a jury later decides that no reasonable person would have shared that belief. What crime has he committed, if any? Murder seems too harsh for someone who thought his life was at stake, and acquittal seems too generous for someone whose belief the law refuses to call reasonable. The answer comes from the homicide map. At common law, murder was the unlawful killing of a human being with malice aforethought¹, and an intent to kill is one of the mental states that supplies that malice.² Malice aforethought is a term of art, so a killing need not be spiteful or planned in advance to carry it.³ An intentional killing is therefore presumptively murder, and the law removes it from that category in only two ways: the killing is lawful, as in perfect self-defense, or it is mitigated to manslaughter, as in a killing committed in the heat of passion.⁴

The defendant described above fits neither exit cleanly, and a mitigating doctrine sits in the gap. In some jurisdictions, a defendant who honestly but unreasonably believed that deadly force was necessary in self-defense is guilty of voluntary manslaughter rather than murder.⁵ The label for this rule is imperfect self-defense. It describes force used by someone who makes an honest but unreasonable mistake about whether force is necessary, in contrast to perfect self-defense, where the defendant accurately appraises both the necessity and the amount of force required.⁶ The doctrine operates only when the defendant has killed, and its function is to reduce what would otherwise be murder to voluntary manslaughter.⁷ Its logic resembles provocation, because both assume the killing was unlawful but find that a mitigating circumstance leaves it without malice aforethought.⁸ Jurisdictions differ on whether they recognize the doctrine at all, and later sections take up that split.

The reason a middle category was needed lies in how the common law treated self-defense. It was an all-or-nothing proposition: a defendant who established the defense was acquitted, and one who fell short of it was left with a murder conviction, however sincere the fear behind the killing.⁹ Imperfect self-defense gives the jury a third verdict between those two. Because the doctrine applies only when the complete defense fails, its operation cannot be understood until the complete defense is clear. This chapter therefore begins with what a perfect self-defense claim requires, so that the element that fails in an imperfect claim can be identified precisely.