Introduction

Self-Defense and Justifiable Homicide

Introduction

An intentional killing is not automatically a crime. Two defendants can each deliberately take a life, and one may be convicted of murder while the other is acquitted, because the law sorts killings according to the circumstances in which they happen, and the intent to kill is only one input. At common law, courts divided homicide into three categories. Justifiable homicide covered killings the law expressly commanded or authorized. Excusable homicide covered killings for which the law recognized a defense that eliminated criminal liability. Criminal homicide was the residual group, every other unlawful killing that fit neither of the first two.¹ The label therefore decides whether the defendant faces punishment at all, so the first question in any homicide problem is which category the facts belong in.

Self-defense is the principal route into the justified category. A person who kills to ward off an attack is doing something the law authorizes, which places the killing on firmer ground than a wrong the law has agreed to forgive. The governing text for this chapter is Model Penal Code § 3.04(1), which makes the use of force upon or toward another person justifiable when the actor believes that the force is immediately necessary to protect himself against the use of unlawful force by that other person on the present occasion.² That sentence contains four working parts: the actor's belief, the immediate necessity of force, the unlawfulness of the force being resisted, and the present occasion on which all of it must be true. The provision also opens by making itself subject to the rest of Section 3.04 and to Section 3.09, and the remainder of the section supplies the limits that narrow the basic rule.³

The chapter follows the order in which the inquiry runs. It first sorts killings into the three categories, because the classification shows what a successful claim of self-defense accomplishes and where a failed claim lands. It then builds the basic self-defense inquiry one part at a time, and finally adds the limits that apply once deadly force is involved: the restriction on deadly force itself, the loss of the defense by the initial aggressor, the duty to retreat in some jurisdictions, and the home exception that relaxes that duty. The category sort comes first, beginning with the killings the law treats as justified.