§ 18.01 General Principles

§ 18.01 General Principles

[A] Overview

Every state in the United States recognizes a defense for the use of force, including deadly force, in self-protection. Abolition of the defense—"thereby leaving one a Hobson's choice of almost certain death through violent attack now or statutorily mandated death [or life imprisonment] through trial and conviction of murder later"¹—seems impossible to imagine. Indeed, if a state legislature were to abolish the defense of self-defense, it would almost certainly violate the United States Constitution.²

Most issues regarding the application of defensive force arise in the context of homicide and attempted murder prosecutions. Therefore, this chapter focuses primarily on the question of when deadly force may be used in self-defense.

[B] Elements of the Defense

At common law, the general rule is that a non-aggressor is justified in using force upon the aggressor if he reasonably believes such force is necessary to protect himself from imminent use of unlawful force by the other person, and such force is proportional to the threat.³ Specifically, deadly force is only justified in self-protection if the actor reasonably believes that its use is necessary to prevent imminent and unlawful use of deadly force or force likely to cause serious bodily injury (which is often treated as falling within the definition of "deadly force"⁴) by the aggressor.⁵ Most states today, by statute, also expressly permit use of deadly force to repel various offenses that carry the risk of serious bodily injury or death, such as an imminent kidnapping, forcible rape, and robbery.⁶

These principles are subject to substantial clarification, as discussed in the next chapter section. However, it should be noted at the outset that the defense of self-defense, as is the case with other justification defenses, contains: (1) a "necessity" component; (2) a "proportionality" requirement; and (3) a reasonable-belief rule that overlays the defense.

[C] The Necessity Component

The necessity rule provides that force should not be used against another person unless, and only to the extent that, it is necessary.⁷ One aspect of this requirement—one that is increasingly controversial—is that self-defense is limited at common law to imminent threats.⁸ Moreover, a person may not use deadly force to combat an imminent deadly assault if some nondeadly response will apparently suffice.⁹ And, in some jurisdictions, a person may not use deadly force against an aggressor if he knows that he has a completely safe avenue of retreat.¹⁰

[D] The Proportionality Component

The proportionality rule provides that a person is not justified in using force that is excessive in relation to the harm threatened.¹¹ Assuming all of the other elements of the defense apply, a person may use non-serious force to repel a minor physical threat; he may also use such force against a deadly threat (and, in some circumstances may...