In the next few sections, we will explore situations in which the commission of what might otherwise be a crime does not result in punishment. Broadly speaking, the doctrines in this area of criminal law are grouped into “justification” and “excuse.” In this section, we will discuss the first kind of justification: self-defense.

Self-defense justifies a crime—more than excusing it, it affirms that what would otherwise be a criminal act is in fact desirable in a given situation. In cases of legal self-defense, our system treats a person who kills or injures as morally right, even when they kill intentionally.

Legalizing assault, killing, or other forceful actions inevitably devolves the state’s usual monopoly on the legitimate use of force, to individual persons capable of abusing it. Thus, legal self-defense raises several concerns. Should self-defense be a last resort? Must the defender respond with minimal force, or is any amount of force legitimate? Must the threat be actual, subjective, or objectively reasonable?

Different jurisdictions have created different systems. Compare the questions raised by situations such as ongoing abusive domestic relationships or an encounter with a stranger on the subway. As you read the following cases, consider the criminal system’s difficulty in managing individuals’ legal use of force, and notice how the law attempts to channel and contain that Pandora’s box.

Necessity may also justify action that would otherwise be criminal. The category is significantly narrower than self-defense, and claims of necessity are rarely successful. Necessity requires imminent and grave harm that results through no fault of the defendant. The defendant must take forceful action only when the benefits clearly outweigh the harms.

As you will see, the cases in this section often deal with significantly more extreme fact patterns than the self-defense cases. Why is the necessity justification narrowly construed?