§ 17.04 Justification Defenses and Mistake-of-Fact Claims

§ 17.04 Justification Defenses and Mistake-of-Fact Claims³¹

[A] General Rule

Consider the following hypothetical: D intentionally kills V. At trial, D claims that she killed V because she believed that V was about to kill her. In fact, V was not about to kill D. This very common scenario involves the convergence of two "defense" concepts: a traditional justification defense (here, self-defense) and a mistake-of-fact claim (D's erroneous belief that V posed an imminent unlawful deadly threat).

Two questions arise when a defendant asserts a justification defense, and yet also claims a mistake of fact: (1) Is a defendant entitled to be acquitted if she was mistaken regarding the facts that would justify her conduct?; and (2) If she is entitled to be acquitted, should the law describe her conduct as justified or excused? For current purposes, these questions will be answered in relation to self-defense (considered fully in Chapter 18), but the principles here have application to the other justification defenses, as well.

The law is clear-cut in situations of the sort described here. A defendant is entitled to be acquitted on the basis of self-defense if her mistake of fact regarding the threat was reasonable. However, she will be convicted of some form of criminal homicide if her mistake was unreasonable.³² More specifically, the rule is that a defendant is justified—and not merely excused—in using deadly force if, at the time of the homicide, she genuinely and reasonably believed that she was in imminent danger of death or grievous bodily injury, and that deadly force was necessary to repel the threat, although it turned out later that these appearances were false.

[B] Criticisms of the General Rule

There is little disagreement with the principle that a defendant who acts on the basis of reasonable appearances should be acquitted, but there is debate about the propriety of treating such a mistaken actor's conduct as justifiable, rather than excusable. In the self-defense hypothetical at the beginning of this section, how can it be that D is justified in taking V's life if V was, in fact, an innocent person who intended no harm?

Critics of the general rule that a person is justified in acting on the basis of reasonable, albeit inaccurate, appearances, argue that it confuses the difference between justifications, which go to the propriety of the defendant's act, and excuses, which relate to the blameworthiness of the actor. These critics maintain that a...