Concept
Beyond But-For Causation
Proximate cause and divergence of result
Beyond But-For Causation
The general rule of § 2.03(1) has two paragraphs, and the second is a pointer to other rules. Paragraph (b) says that conduct is the cause of a result only if the relationship between the conduct and the result satisfies any additional causal requirements imposed by the Code or by the law defining the offense.1 The sentence directs the reader to two places. The first is the rest of § 2.03, which compares the result that actually occurred with the result the actor designed, contemplated, or risked. The second is the statute that defines the particular crime, which may carry a causal condition of its own, and the Code leaves legislatures free to attach such traditional causal elements if they choose.2 A fixed rule of that kind is an older way of expressing the idea that a result can stand too far from the act to be charged to the actor. The common-law year-and-a-day rule for deaths is one example, and it is treated separately. The word additional matters because it makes the but-for requirement of paragraph (a) a floor that every result offense must clear, and the floor is only the beginning of the inquiry.
The Code can state only a floor in paragraph (a) and then point onward because it regards but-for causation as the only strictly causal requirement that should be imposed generally. What remains is the proper scope of liability in light of the actor's culpability.3 Scope of liability depends on culpability because the same gap between plan and outcome means different things for different actors. A person who designed a death stands differently toward an unexpected route to that death than a person who only ran a risk of one, so a single statement of how far liability reaches would fit some offenses badly. The Code therefore writes the comparison separately for each mental state. The provision New Jersey derived from the Code shows the structure: one rule for results caused purposely or knowingly, another for results caused recklessly or negligently, and a third for offenses of absolute liability.4
The two layers can fail independently, and a decided case shows how the dispute moves from one to the other. In State v. Martin the defendant acknowledged that the death of Quartz would not have occurred but for the fact that he set a fire.5 The first layer was therefore satisfied, and the contest shifted to the additional requirement. Because the charge was knowing or purposeful murder, the New Jersey provision, which is based substantially on the Model Penal Code, asked whether the actual result was within the actor's design or contemplation or, if not, involved the same kind of harm and was not too remote, accidental in its occurrence, or dependent on another's volitional act to bear justly on liability or on the gravity of the offense.6 The opinion also states the point that organizes the rest of this chapter: causation is a term of art whose meaning varies with the mental state of the actor, meaning one thing for a knowing or purposeful offense and something else for a crime of strict or absolute liability such as felony murder.7
The contrast with Martin shows what each layer does. A culpable state of mind cannot repair a missing but-for link, so when paragraph (a) fails, the analysis ends. When paragraph (a) is met, as it was in Martin, the actor's conduct has been shown to matter to the result, and paragraph (b) asks whether the way it mattered is one for which the actor should answer.
Most cases never need paragraph (b). When a healthy victim is shot through the heart by someone aiming at the heart, the actual result is exactly the intended one and the causal connection is easy to show.8 Additional analysis is required only when the result that occurs differs from the one intended or contemplated.9 The difficult cases are the unusual ones: a wound that would not have been fatal except that the victim was already weakened by sickness, a doctor who treats the wound negligently, a victim who dodges a bullet by diving into a river and drowns, or a shooter who misses and kills someone else.10 Each of these is a but-for cause of the harm. In each, the open question is whether the departure from the plan leaves the actor fairly answerable, and the sections that follow take up those departures in the order the Code does.
Courts and commentators usually call this second layer proximate cause or legal cause, and the label invites a misreading. Students lose this issue when they read the word proximate as physical or temporal closeness between act and result. The doctrine has little to do with nearness in time or space, and it arises only after cause in fact is established, as a question of fairness about how far responsibility should extend.11 The Code asks that question through culpability. Courts that have addressed the point generally define proximate causation more narrowly in criminal law than in tort, because criminal liability punishes while tort liability ordinarily only compensates.12 This chapter next applies the comparison between actual and expected result, beginning with the most culpable mental states, purposely and knowingly, where the baseline is the result the actor designed or contemplated.