by Richard W. Wright
Editor’s note: The following is an excerpt from Part II of Professor’s Wright “Causation in Tort Law.” Please consult the original for the rest of the article and its footnotes.
A. The But-For Test and Its Limits: Duplicative and Preemptive Causation
The most widely used test of actual causation in tort adjudication is the but-for test, which states that an act (omission, condition, etc.) was a cause of an injury if and only if, but for the act, the injury would not have occurred. That is, the act must have been a necessary condition for the occurrence of the injury. The test reflects a deeply rooted belief that a condition cannot be a cause of some event unless it is, in some sense, necessary for the occurrence of the event. This view is shared by lawyers, philosophers, scientists, and the general public.
In the vast majority of cases, the but-for test works quite well as a test of actual causation. But in certain types of cases, it results in a finding of no causation even though it is clear that the act in question contributed to the injury. These are cases of overdetermined causation: cases in which a factor other than the specified act would have been sufficient to produce the injury in the absence of the specified act, but its effects either (1) were preempted by the more immediately operative effects of the specified act or (2) combined with or duplicated those of the specified act to jointly produce the injury.
I will refer to the first type of situation as a case of preemptive causation. For example, D shoots and kills P just as P was about to drink a cup of tea that was poisoned by C. D’s shot was a preemptive cause of P’s death; C’s poisoning of the tea was not a cause because its potential effects were preempted. I will refer to the second type of situation as a case of duplicative causation. For example, C and D independently start separate fires, each of which would have been sufficient to destroy P’s house. The fires converge and together burn down the house. Each fire was a duplicative cause of the destruction of the house. Yet, application of the but-for test would result in a finding that D’s shot was not a cause of P’s death in the first example and that neither C’s nor D’s fire was a cause of the destruction of P’s house in the second example.
A different sort of objection to the but-for test focuses on the hypothetical or counterfactual nature of the inquiry that the test calls for. A number of writers have asserted that the hypothetical nature of the but-for inquiry necessarily involves or at least invites introduction of policy considerations into a supposedly factual inquiry.
While it might be thought that these difficulties could be avoided by substituting a sufficient condition test for the but-for necessary-condition test, this substitution would eliminate almost every potential cause, since few if any acts are sufficient by themselves to produce any particular consequence. Thus, in the scientific and philosophic literature on causation, it is usually stressed that the cause of an event must include all the conditions which together are sufficient to produce the consequence. Consequently, both lawyers and philosophers often conclude that this scientific or philosophic concept of causation is of little relevance or use in the law.
On the other hand, the sufficient-condition test could be interpreted to mean any condition that is sufficient in combination with other conditions to produce the consequence, even though it is not sufficient by itself. Under this interpretation, however, anything could be treated as a cause simply by adding it to an already sufficient set of conditions.
Judges and legal writers have responded to the actual and perceived deficiencies in the but-for test in several different ways. A few writers have tried to improve the but-for test by modifying the manner in which it is applied. Most judges and writers, however, have adopted the substantial-factor formula, either as a supplement to or as a substitute for the but-for test depending on their degree of dissatisfaction with the but-for test. Others have relied on an undefined and irreducible notion of directly observable causal contribution.
Each of these approaches will be discussed in subsequent sections of this Part. It will be demonstrated that, under each approach, the analysis ultimately must fall back on the but-for test in order to be useful and coherent. The necessary-condition element, in some form, indeed seems to be fundamental to the concept of causation. But it obviously is too restrictive when applied in the usual way to the overdetermined-causation cases. Some writers treat the overdetermined-causation cases as genuine instances of causation that must be admitted as unexplained exceptions to the but-for test. A larger and growing number of writers treat the overdetermined-causation cases as policy-based exceptions to the actual-causation requirement, which is equated with the but-for test.
B. Efforts to Modify the But-For Test
As mentioned above, the but-for test works well as a test of actual causation in the vast majority of cases, but produces obviously incorrect results in the overdetermined-causation cases. A few writers have tried to extend the but-for test’s range of application by modifying the way in which it is applied. Rollin Perkins, Arno Becht, and Frank Miller apply the test to a detailed description of the injury or the manner of its occurrence. Glanville Williams excludes consideration of hypothetical facts. And the editors of the fifth edition of Prosser’s hornbook on tort law apply the test to multiple potential causes in the aggregate. None of these approaches works. Several of them assume the very answer the test is supposed to provide.
1. Detailing the Manner of Occurrence
Perkins tries to resolve the causal issue in the overdetermined-causation cases by detailing the manner in which the injury occurred: “Whenever that would not have happened when and as it did happen, had it not been for this, this is an actual cause of that.” For example, if a victim is killed instantaneously by a bullet wound while already dying from a knife wound, he would not have died, as he in fact did, at the earlier moment and by a bullet wound if not for the firing of the bullet. Without the bullet wound, he would have died later, from the effects of the knife wound. This, however, did not in fact happen. Thus, the bullet wound, but not the knife wound, is a but-for cause of the death “when and as” it happened.
This form of reasoning is nothing more than proof by tautology. For example, consider Perkins’ treatment of the case in which the victim is struck simultaneously by two bullets, each of which would have been instantly fatal by itself: “[He] would not have died when and as he did die (by two bullets) had only one been fired. ‘One might have caused the result, but in fact both did so.’” The factors believed to be causally relevant (the two bullets) are incorporated into the description of the manner of occurrence of the injury (death by two bullets), and they are then demonstrated to be causally relevant because we cannot construct that precise description without them.
Such an approach could just as easily have included the victim’s knife wound, his silk shirt, or the air temperature in the description of the manner of occurrence of the injury. If so included, each of these conditions would also be proven under Perkins’ test to be but-for causes of the harm. We do not include them because we do not believe they were causally relevant. But that is precisely the issue the test is supposed to determine. The test “proves” only what has already been decided. It does not tell us how that decision was made or help us to make it in hard cases.
2. Detailing the Injury
Becht and Miller accept Perkins’ reasoning, but they focus more on the details of the harm itself—the final result—than on the manner of its occurrence. For example, in the case of the two fires, one set by the defendant and each sufficient to destroy the plaintiff’s house, Becht and Miller assert that, using the but-for test applied “in minute detail, it would probably appear that the defendant’s fire was a cause, for the positions of the smoke, ashes, and some parts of the ruins might well have been caused by [i.e., not have existed but for] the defendant’s fire.”
Again, this assertion begs the question. Under this approach, the defendant’s fire was a but-for cause only of the precise “positions of the smoke, ashes, and some parts of the ruins,” not of the destruction of the house, for which these precise details are irrelevant. The detailed description will be useful only if the plaintiff wishes to recover for damages that would not have occurred but for the precise position of the smoke and debris—a most unlikely lawsuit.
If being a but-for cause of even the most trivial detail of a harm were sufficient to make the defendant a cause of all the harm, the detailed but-for approach would prove too much. Becht and Miller discuss an example in which an inattentive driver hits a pedestrian who suddenly ran into the path of the driver’s car. If the driver had been attentive, he could have swerved a little, but not enough to avoid impact with serious injury. Nevertheless, a detailed application of the but-for test shows that the driver’s inattentiveness “was a cause of the injuries actually suffered,” since “the injuries would have been at least slightly different and would have been inflicted by different parts of the car if the driver had swerved.” Becht and Miller admit that both laypersons and lawyers, using the common knowledge of causation upon which Becht and Miller rely so strongly, would conclude that the driver’s inattentiveness was not a cause in such a case. They suggest that laypersons and lawyers make this mistake by failing to pay careful attention to the precise details. But laypersons and lawyers, even after considering the precise details, would still assert correctly that the inattentiveness was not a cause of the serious injury, although it may have been a (but-for) cause of some details associated with the injury. These details have causal significance only if they contributed to the seriousness of the injury.
Becht and Miller realize that they, rather than the laypersons and lawyers, must give way on this issue. They compromise their usual causal principles by “equating the injuries.” They reluctantly disregard minor differences and conclude that the inattentiveness was not a cause. Although they do not acknowledge it, they thereby destroy the alleged usefulness of the minute-detail approach. After utilizing the minute-detail approach to support a finding of causation, they then are forced to ignore the details and reject causation by equating the injuries. The concept of “equating the injuries” introduces an inconsistency into their theory that undermines their use of the minute-detail approach to support a finding of causation in the merged-fires case.
3. Excluding Hypothetical Facts
Glanville Williams also refers to Perkins’ approach of detailing the manner in which the harm occurred, but he proposes a different approach for the preemptive-causation cases. In such cases, facts that did not actually occur must not be “invented” and considered, no matter how likely they were to occur. Thus, the hypothesized but almost certain fact that P would have been shot by C if he hadn’t already been shot by D cannot be considered. However, on the very next page, Williams is obliged to depart from this rule to reach the correct causal conclusion in a case of negligent omission. Moreover, such a rule is of no help at all in cases where the preempted condition actually has occurred—for example, when P actually was shot by C after he already had been shot and killed by D. In this type of preemptive-causation case, and in the duplicative-causation cases, Williams abandons the but-for test for actual causation and treats the causal issue as a policy issue.
4. Aggregating Multiple Potential Causes
The editors of the fifth edition of Prosser’s hornbook on tort law attempt to resolve the causal issue in the overdetermined-causation cases by applying the but-for test to the aggregate of potential causes:
When the conduct of two or more actors is so related to an event that their combined conduct, viewed as a whole, is a but-for cause of the event, and application of the but-for rule to them individually would absolve all of them, the conduct of each is a cause in fact of the event.
This version of the but-for test, like Perkins’s version, works only if the person applying the test already has correctly determined which factors are sufficiently “related” to the event to be treated as its causes. On its own, the test cannot distinguish duplicative causes from preempted conditions. Moreover, it would treat totally unrelated conditions as causes.
For example, consider the case in which C poisons P’s tea and D shoots P before P drinks the tea. Assume also that B was climbing Mt. Everest. Clearly, D’s shooting P was a preemptive cause of P’s death, and neither C’s poisoning the tea nor B’s climbing Mt. Everest was a cause. The proposed test, however, would treat all three activities as causes. In the aggregate they were a but-for cause of P’s death, while individually none of them was a but-for cause.
C. The Substantial-Factor Formula
Those theorists and judges who are unwilling to engage in contortions such as the ones illustrated above to rescue the but-for from its inadequacies usually have turned to the substantial-factor formula, either as a supplement to the but-for test (to apply to the overdetermined-causation cases) or as a complete substitute for it.
The substantial-factor formula was created originally not as a test of actual causation but as a guide for resolving proximate-cause issues. The originator of the formula, Jeremiah Smith, was content with the but-for test as a test of cause-in-fact, with the usual exception for the overdetermined-causation cases. He wanted to devise a practical alternative to the probability or foreseeability tests for determining the proximate-cause limitations on liability, because he believed that those tests were unsound and inconsistent with the results in many cases. He proposed the following formula: “Defendant’s tort must have been a substantial factor in producing the damage complained of.” The accompanying explanation and alternative formulations clearly stated that the defendant’s tort could not be a substantial factor unless it satisfied the but-for test (with an exception for simultaneous independent sufficient causes); in addition, it would have to be an appreciable and continuously effective or efficient factor in producing the harm, up to the time of occurrence of the harm.
Thus, the substantial-factor formula was meant to be used as the test of legal (proximate) cause, but also incorporated the but-for test (and its exception) for cause-in-fact. Smith’s approach was adopted essentially intact in the original Restatement of Torts. It has persisted in the Restatement (Second) of Torts’ treatment of legal causation and cause-in-fact, despite an attempt by Prosser and others to confine the substantial-factor formula to the question of causation-in-fact.
Leon Green first suggested that the substantial-factor formula be applied to the actual-causation issue. He completely rejected the but-for test, since it “take[s] the eye off the ball” by asking what would have happened rather than focusing on what did happen and thereby denies causation in many cases where causal contribution to the injury is obvious. In his view, the substantial-factor formula was the best available alternative. He argued that it should be used without elaboration to pose the issue of causal contribution to the jury in every case, not just in the overdetermined-causation cases. Green’s view was accepted by Prosser, who passed it on to several generations of law students and lawyers through the various editions of his hornbook, even after Green himself became disenchanted with the formula.
The problem with the substantial-factor formula as a test of actual causation (apart from its complete lack of guidance on what constitutes a “factor”) is that the alleged cause must be a substantial factor. Thus, paradoxically, at the same time that Green was arguing strenuously and cogently that the issue of causation should be completely divorced from the policy issues camouflaged in proximate-cause analysis, he adopted a formula for actual causation that required the judge or jury to determine not only whether the actor’s tortious conduct had contributed to the injury (been a factor), but whether it had contributed enough to make the actor responsible—whether, “in the light of all the other factors, the defendant’s conduct played an appreciable part in the result.” Green seemed to believe that the resulting inquiry retained its character as a factual, causal inquiry because it allegedly relied on quantitative rather than qualitative measures of relative contribution.
Even if quantitative measures of relative contribution are used, however, the question of limiting liability due to the extent of contribution, rather than due to the absence of any contribution, is clearly a proximate-cause issue of policy or principle, rather than an issue of actual causation (contribution to the injury). Moreover, the substantial-factor formula inherently invites consideration of qualitative measures as well as quantitative ones.
Green himself, immediately after emphasizing the quantitative nature of the inquiry, used qualitative considerations when discussing a series of cases involving multiple causes. For example, he asserted that it is “perhaps clear” that the hole poked by D’s tug in P’s barge, three feet above the water line, was not an appreciable factor in the sinking of the barge when compared with the continued loading of the barge which brought the hole below the waterline, since those who were loading the barge were fully conscious of what had occurred but made no effort to repair the hole. Similarly, he suggested that there would be little possibility of a finding that D’s driving over a small flat box, which unbeknown to him contained a highly explosive substance, was a substantial factor in producing the resulting explosion. And, when discussing the cases in which P is negligently or intentionally pushed by X into a hole negligently maintained by D, Green stated that “what would be considered appreciable in one case might not in another. So, as compared with X’s negligence, [D’s] conduct might be considered appreciable, while as compared with X’s intended violence, [D’s] conduct might not be so considered.”
In each of these cases, the defendant’s tortious act was a necessary condition for the occurrence of the injury. When an act (omission, condition) was a necessary condition for the occurrence of an injury, it is unnatural to deny that the act was, as a matter of fact, not only a factor in producing the injury, but also a substantial or appreciable factor. To state otherwise is to make a non-causal, nonfactual policy judgment about responsibility for the injury.
Prosser and, eventually, Green seem to have recognized the emptiness of the undefined substantial-factor formula and the danger of its being used to introduce proximate-cause issues into the actual-causation inquiry. Prosser, in the various editions of his hornbook, concluded his brief discussion of the formula by equating it with the but-for test, with an exception for the overdetermined-causation cases, and in his articles he relied primarily on the but-for test.
In his later writings, Green abandoned his earlier substantive interpretation of the substantial-factor formula. He treated it as a meaningless label for the judge to attach to her determination on the actual-causation issue or to use as a hortatory device “to caution a jury to weigh the evidence carefully.” He also criticized the view that the causal inquiry involves not only the question of contribution to the injury, but also the question of how significant the contribution was, without noting that he previously had been the major proponent of this view. However, he continued to reject the but-for test and to insist that the issue of causal contribution be submitted to the jury without any elaboration or guidance.
D. Undefined, Directly Observable Causal Contribution
Lacking any satisfactory test, Green and a few other writers have treated causation as an undefinable and irreducible factual relation between events that can be directly perceived or inferred without explicitly or implicitly resorting to any generalization, definition, or test. Most of these writers do not attempt to explain how this concept would be applied in the various types of causation cases. However, there is one notable exception: Becht and Miller’s book, The Test of Factual Causation.
Becht and Miller’s book is a comprehensive attempt to demonstrate how the concept of undefined, directly observable causal contribution is applied in tort analysis. They argue that we determine whether a causal relation exists between an act and an injury by breaking down the sequence of events to the appropriate level of detail to see if we can “perceive” a causal connection. If we can, the act is deemed to be a cause of the injury even if the injury can also be traced back to another act or event through a different causal sequence as in the merged-fires case. However, when Becht and Miller attempt to show how this approach would work in the myriad variety of actual-causation cases, they are forced to rely on the but-for test in an increasingly wide range of cases.
Initially, they are forced to use the but-for test to handle causal inquiries involving omissions. By definition an omission is a nonevent—something which did not happen—which only rarely will trigger an actual causal sequence that can be directly perceived or traced. Instead, an omission is almost always a “negative” cause of an injury: it represents a missed opportunity to prevent the injury. That is, an omission is a cause of an injury only if the omitted act would have been part of a hypothetical causal sequence that would have prevented, terminated, or deflected the different causal sequence that actually occurred and produced the injury. Thus, in order to determine whether an omission was a cause of an injury, it is necessary to conduct a hypothetical inquiry. The omitted act must be hypothetically supplied, and a hypothetical causal sequence (which Becht and Miller call a “parallel series”) must be constructed and traced to determine whether it would have prevented the occurrence of the injury.
The hypothetical inquiry (but-for test) also must be used whenever an actual (“positive”) causal sequence becomes a negative cause by blocking or terminating some preventive effort for example, by blocking a fire engine or cutting off its supply of water. This inquiry also must be employed to determine whether the excess (negligent) portion of a certain speed or weight, or the difference between being in a safe position or an unsafe (negligent) position, contributed to the injury. Indeed, as Becht and Miller reluctantly admit, the hypothetical inquiry must be used whenever the negligent aspect of an act does not encompass the act as a whole. For example, in the excess-speed case, the act is driving at a certain speed. We observe the car at that speed hit the child. The negligent aspect of the speeding is the excess speed, which Becht and Miller note “is not an extent but a concept. Like an omission, it did not happen, and it cannot be a simple [perceived] cause of events in the world.”
Becht and Miller recognize the possible criticism that they are implicitly using the hypothetical inquiry with all negligent acts, rather than just with negligent acts that have a non-negligent aspect, “but are unconscious of [doing so] when the [hypothetical inquiry] shows clearly that the negligent act was a cause of the harm.” They admit that they cannot disprove this contention, but they continue to claim that they are using direct perception of causation in such cases. However, they have some difficulty with a case in which the defendant negligently welds the roof of a car, leaving a sharp edge, and the driver’s head is crushed against the roof at the weld point when the roof is smashed in during an accident. They steadfastly assert that the case is one in which direct perception or inference, unaided by any hypothetical inquiry, shows a lack of causation by the sharp weld, just as direct perception or inference shows that the color of the roof was not a cause of the injury.
The direct-perception argument relies on the notion that there are observable and describable causal qualities or forces in objects or events. Becht and Miller eventually concede that this notion is naive as compared with the Human account, which is based on causal generalizations. Even if the direct-perception notion were creditable, it is difficult to imagine how the lack of causation by the sharp weld could be perceived in the circumstances given. It is also difficult to understand what is meant by “direct inference.” An inference is based on some concept of how things generally happen—that is, on causal generalizations. Causal generalizations incorporate the belief that the cause is in some sense necessary for the occurrence of the consequence. The but-for test is simply the means by which we determine whether this element of necessity exists in the particular case.
Becht and Miller argue that, even if it is true that they are explicitly or implicitly using the but-for test in every case, they are using a less restrictive version. Unlike the usual version, they compare what happened with what would have happened in as minute detail as possible. Moreover, in those cases in which there was more than one positive causal sequence that led to the injury, they only require that the defendant’s act or omission have been necessary for the continuation of the positive causal sequence with which it was associated, rather than requiring that it have been necessary for the injury itself.
The first distinction—their use of minute detail—is nullified by their tactic of “equating the injuries” to avoid finding but-for causation whenever there is a slight difference between the actual process or result and the hypothesized process and result.
The second distinction, however, is a real one. It enables them to find that causation exists in many of the overdetermined-causation cases. For example, in the merged-fires case the defendant’s tortious conduct will be treated as a cause of the destruction of the house if it was a but-for cause of one of the fires, even though the house would have been burnt down by the other fire anyway. The defendant’s tortious conduct was a but-for cause of one of the duplicative causal sequences, and that is sufficient to establish the causal connection to the destruction of the house.
Becht and Miller’s causal-contribution analysis ends up being very similar to the “necessary element of a sufficient set” test. However, it is not exactly equivalent. Indeed, it produces anomalous results precisely to the extent that it varies from the latter test. Becht and Miller’s approach requires that the tortious act or omission have been a necessary condition for one of the positive (actual) causal sequences that contributed to the injury. They are therefore forced to deny that causation exists when the overdetermined-causation problem results from duplicative or preempted conditions that affect the same positive causal sequence, rather than from the existence of multiple positive causal sequences.
For example, they discuss the case in which C negligently fails to discover and repair defective brakes in a car before renting the car to D, who, unaware of the defective condition of the brakes, negligently fails to try to use them to avoid hitting P. P is hit, but he would not have been hit if the brakes had been working properly and D had used them. C’s omission (the failure to inspect and repair the brakes) was not a necessary condition for the occurrence of the positive causal sequence that produced the injury, since D made no attempt to use the brakes. Similarly, given C’s omission, D’s omission (the failure to try to use the brakes) was not a necessary condition either. Becht and Miller unhappily but firmly conclude that neither omission was a cause of the injury, but would hold both C and D liable to avoid a “morally indefensible” and “inexcusable” result.
The same problem occurs with acts. Assume that a cable has a maximum safe load capacity of one ton when it is in good condition. C negligently weakens the cable (for example, by cutting a few of its strands) so that it will now break if a one-ton load is applied. D negligently overloads the cable with a two-ton load, which would cause it to break even if it were in good condition. The cable breaks at the weakened point, and the load falls on and injures P. Since the negligent acts of C and D are both part of the same positive causal sequence that produced the injury, but neither was a necessary condition for the occurrence of the sequence, neither is a cause of the injury under Becht and Miller’s approach.
Becht and Miller’s book contains illuminating discussions on many points—for example, the distinction between acts and omissions and the need to focus on the tortious aspect of the actor’s conduct. Perhaps its most valuable contribution, however, is an unintended one: the demonstration of the unavoidability of the but-for (necessary condition) test in causal analysis. This unavoidability is most clear when the causal inquiry focuses on omissions or the tortious aspect of acts, but it is implicit in all causal inquiries.
E. The NESS (Necessary Element of a Sufficient Set) Test
In this section, I turn at last to a test for causal contribution that is applicable to the entire spectrum of causation cases. This test incorporates the indispensable notion of necessity, but subordinates it to the notion of sufficiency. I call this test the NESS (Necessary Element of a Sufficient Set) test.
The NESS test was first suggested by H.L.A. Hart and Tony Honore. However, their brief exposition of this test was overshadowed and distorted by their primary emphasis on proximate-cause issues. The test has received very little notice and even less acceptance in the subsequent legal literature. One of the principal purposes of this Article is to draw renewed attention to the NESS test, by demonstrating its fundamental identity with the basic concept of causation and its utility in resolving the cases that have proved troublesome for several generations of tort scholars.
1. The Philosophic Basis of the NESS Test
The NESS test captures the essential meaning of the concept of causation. This meaning was first articulated by the philosopher David Hume. Hume rejected the earlier notion that we acquire causal knowledge through direct sensory perception of causal qualities or forces inherent in objects or events. Instead, he insisted that we only observe certain successions of events, more or less frequently repeated. From these observations, we inductively derive the belief that certain antecedent events are not only always conjoined with, but also are sufficient for the occurrence of, certain subsequent events. That is, we form a belief in more or less well-grounded causal laws or generalizations. Causal knowledge or belief also can be based on reasoning by analogy from such observations or can be acquired through education, which passes on the causal knowledge of others. Any singular causal statement about a particular occurrence is not a reporting of direct sensory perception of causal forces, but rather an assertion of the belief that the occurrence instantiates one or more causal laws or generalizations.
A fully specified causal law or generalization would state an invariable connection between the cause and the consequence: given the actual existence of the fully specified set of antecedent conditions, the consequence must follow. In other words, the fully specified set of antecedent conditions is sufficient for the occurrence of the consequence. In the typical singular causal statement, the causal assertion includes, explicitly or implicitly, only a few of the antecedent conditions but nevertheless asserts that they were part of an incompletely specified (and incompletely understood or known) set of actual conditions that was sufficient for the occurrence of the consequence.
Hume was primarily interested in elaborating and defending this “regularity” account of causation and causal knowledge, which insists that the meaning of causation is to be found in causal laws or generalizations rather than in some notion of causal qualities or forces. However, while pursuing this primary objective, he occasionally noted that one must be careful when constructing a causal law or generalization to distinguish the causally relevant antecedent conditions from the causally irrelevant antecedent conditions. This differentiation is necessary to insure that the set of jointly sufficient antecedent conditions includes only those that are indeed invariably connected with the consequence. Thus, the antecedent conditions must be restricted to those that are necessary for the sufficiency of the set.
Hume also maintained that a certain consequence is always produced by the same cause—that is, that there is a unique sufficient set of antecedent conditions that always must be present to produce a particular consequence. Hume’s successor, John Stuart Mill, disagreed. He asserted that there may be a plurality of potential causes for any consequence. For example, death may be caused by poison on one occasion, by a bullet wound on another, by fire on yet another, and so forth. Hume’s defenders have argued that such seemingly different causes may upon further investigation turn out to be overly broad specifications of a single common cause, or that the seemingly identical consequence may turn out to be distinct consequences. However, they also admit that ordinary experience provides strong support for the plurality-of-potential-causes theory. Indeed, the plurality theory has become part of the dominant “regularity” account of the meaning of causation.
As Hart and Honore noted in 1959, the “necessary element of a sufficient set” (NESS) test of causal contribution follows directly from this dominant “regularity” account of the meaning of causation. The essence of the concept of causation under this philosophic account is that a particular condition was a cause of (condition contributing to) a specific consequence if and only if it was a necessary element of a set of antecedent actual conditions that was sufficient for the occurrence of the consequence. (Note that the phrase “a set” permits a plurality of sufficient sets.) This is the more precise, extended statement of the NESS test.
Surprisingly, however, this notion of a contributing condition appears only infrequently in the philosophic literature on causation. The literature continues to be characterized by arguments based on necessary conditions, sufficient conditions, or necessary and sufficient conditions. After Hart and Honore’s book was published, several non-legal philosophers articulated NESS-like notions of causal contribution. In each instance, however, they burdened the NESS test with the additional requirement that the sufficient set be necessary for the occurrence of the consequence in the particular circumstances. This requirement converts the NESS test to a necessary and sufficient condition test, which cannot accommodate the duplicative-causation cases (for example, the merged-fires cases).
Hart and Honore do not make this mistake, because they recognize that there may be a plurality of causes in a particular instance. However, their version of the NESS test is also deficient in several respects. First, they apparently require that a duplicative or preemptive cause be independently “sufficient” for the occurrence of the injury. That is, it must be sufficient in conjunction with the “background” conditions, but excluding the duplicated or preempted conditions. Second, they submerge the critical distinction between duplicative and preemptive causation by constructing an overlapping typology of overdetermined-causation cases. Finally, they confuse the factual issue of causal contribution with the issues of policy or principle involved in determining ultimate liability in certain types of cases.
2. The Duplicative-Causation Cases
As elaborated, Hart and Honore’s NESS test is only slightly less restrictive than the Restatement’s substantial-factor exception to the butfor test, which only applies when each of two actively operating factors was sufficient by itself for the occurrence of the injury. Hart and Honore do not require that each of the factors have been actively operating, but they seem to require that each have been sufficient by itself for the occurrence of the injury. For example, in the merged-fires cases, they assume that each fire would have been sufficient by itself for the destruction of the plaintiff’s house. The NESS test then confirms causal contribution by each fire. Each fire was necessary for the sufficiency of a set of actual antecedent conditions that did not include the other fire.
The requirement that each factor have been sufficient by itself (when combined with the background conditions) is too restrictive and is not a part of the basic concept of causation that is reflected in the NESS test. Moreover, the independent-sufficiency requirement is not followed by the courts. For example, in two duplicative-causation cases involving merged fires and noisy motorcycles, respectively, the courts did not require the plaintiff to prove the independent sufficiency of each contributing factor, but rather required him to prove only that each factor contributed to the injury. Similarly, in the pollution cases, the courts have allowed the plaintiff to recover from each defendant who contributed to the pollution that caused the injury, even though none of the defendants’ individual contributions was either necessary or sufficient by itself for the occurrence of the injury.
Malone argues that the courts’ departure from the but-for test in the overdetermined-causation cases is further evidence of the policy-dependent nature of the causal inquiry. He contends that the courts are willing to replace the but-for test with the substantial-factor formula in cases like the merged-fires cases because of the important policies that underlie “the well-established rules that prohibit the setting into motion of a destructive force.”
But, contrary to Malone’s assertion, the policies or principles at work in these cases are not those underlying the particular rule that was violated. They are the ones underlying the actual causation requirement itself. As Malone himself notes, the courts feel impelled to depart from the but-for test in these overdetermined-causation cases because, although the but-for test is not satisfied, it is clear that the defendant’s tortious conduct contributed to the injury: “Our senses have told us that he did participate… In the language of the layman, the defendant’s fire ‘had something to do with’ the burning of the plaintiff’s property.” Just as Newtonian mechanics serves as an adequate substitute for the more accurate and comprehensive theories of relative and quantum mechanics in ordinary physical situations, the but-for test serves as an adequate substitute for the NESS test in ordinary causal situations. In each context, however, the substitute must give way to the more accurate and comprehensive concept when the situation is more subtle and complex.
In the pollution cases, the NESS test confirms that each defendant’s pollution contributed to the injury, even though it was neither necessary nor independently sufficient for the injury. For example, assume that five units of pollution were necessary and sufficient for the injury and that each of seven defendants discharged one unit of pollution. Each defendant can truthfully say that its one unit was neither necessary nor independently sufficient for the injury. But each defendant’s one unit was necessary for the sufficiency of a set of actual antecedent conditions that included only four of the other units, and the sufficiency of this particular set of actual antecedent conditions was not affected by the existence of two additional duplicative units.
A similar causal situation exists even if one defendant discharges five units of pollution and a second defendant discharges two units. The two units still mix with the five units to produce the injurious seven units. More rigorously, the two units were necessary for the sufficiency of a set of actual antecedent conditions that included only three of the first defendant’s five units, a set whose sufficiency was not affected by the existence of two additional duplicative units also provided by the first defendant.
The analysis of the merged-fires cases is analogous. Thus, if any two of three fires were sufficient for the injury, but none by itself was sufficient, each was a cause of the injury since each was necessary for the sufficiency of a set of actual antecedent conditions that included only one of the other fires. The same causal situation exists even if there were only two fires, one of which was independently sufficient and the other of which was not. The first fire was clearly a cause, since it was independently sufficient. But the second fire also was a cause. It was necessary for the sufficiency of a set of actual antecedent conditions which included another fire (the first) that was “at least large enough to be sufficient for the injury if it merged with a fire the size of the second fire.” The sufficiency of this set is not affected by the fact that the first fire was so large that it would have been sufficient by itself.
The wording of the quoted condition, “at least large enough,” is not a verbal gimmick. The condition is an actual one that existed on the particular occasion. It describes a certain factual situation, as much as the condition in the pollution case that referred to only three of the first defendant’s five units of pollution. In the former case, the size of the first fire is broken down into portions; in the latter case, the amount of the first defendant’s pollution is broken down into portions.
The NESS test would attribute causal status to a very small fire that merged with an overwhelming large fire. The very small fire was a duplicative cause of any resulting injury. Whether the person who tortuously caused the very small fire should be held liable for any or all of the resulting injury is an issue of policy or principle that comes under the heading of damages.
The same analysis applies to the weakened-cable hypothetical. In that example, a cable with a maximum safe load capacity of one ton was weakened by C, who negligently cut a few of its strands so that it would break if subjected to a one-ton load. D then negligently put a two-ton load on the cable, which would have caused it to break even if the cable were in good condition, and the cable broke at the weakened point. C’s weakening of the cable was necessary for the sufficiency of a set of actual antecedent conditions which included a load of at least one ton, and the sufficiency of this set was not affected by the fact that the load was more than one ton. Indeed, the causal contribution of C’s weakening of the cable is evidenced by the fact that the cable broke at the weakened point. Similarly, D’s overloading of the cable was necessary for the sufficiency of a set of actual antecedent conditions that included a cable with a load capacity of at most one ton, and the sufficiency of this set was not affected by the fact that the cable had a capacity of less than one ton as a result of the weakening. C’s weakening of the cable and D’s overloading of it are duplicative causes of the cable’s breaking and the resulting injury to the plaintiff.
3. The Preemptive-Causation Cases
So far, the discussion has concentrated on the duplicative-causation cases. I turn now to the preemptive-caution cases. Hart and Honore mention situations in which the defendant asserts that someone else would have shot the plaintiff or stolen his property if the defendant had not done so. The defendant’s argument would succeed under a literal application of the Restatement, which adheres to the but-for test unless the alternative factor was “actively operating.” But, under the NESS test, the defendant’s tortious act clearly was a cause of the injury, since it was a necessary element of the set of actual antecedent conditions that was sufficient for the injury. Under this test, moreover, only the defendant’s actions would be deemed a cause. The potential actions of others that did not in fact occur could not be a part of any set of actual antecedent conditions that was sufficient for the injury.
Preemptive causation also is present in many cases where the alternative factor actually did occur. For example, in my initial illustration where D shot and killed P just as P was about to drink a cup of tea that had been poisoned by C, D’s shot was necessary for the sufficiency of a set of actual antecedent conditions that did not include the poisoned tea. Conversely, C’s poisoning of the tea was not a necessary element of any sufficient set of actual antecedent conditions. A set that included the poisoned tea but not the shooting would be sufficient only if P actually drank the tea, but this was not an actual condition. The shooting preempted the potential causal effect of the poisoned tea.
Moreover, even if P actually had drunk the poisoned tea, C’s poisoning of the tea still would not be a cause of P’s death if the poison did not work instantaneously but the shot did. The poisoned tea would be a cause of P’s death only if P drank the tea and was alive when the poison took effect. That is, a set of actual antecedent conditions sufficient to cause P’s death must include poisoning of the tea, P’s drinking of the poisoned tea, and P’s being alive when the poison takes effect. Although the first two conditions actually existed, the third did not. D’s shooting P prevented it from occurring. Thus, there is no sufficient set of actual antecedent conditions that includes C’s poisoning of the tea as a necessary element. Consequently, C’s poisoning of the tea fails the NESS test. It did not contribute to P’s death.
As the last example illustrates, a necessary condition for the sufficiency of any set of actual antecedent conditions is that the injury not have occurred already as a result of other actual conditions outside the set. The determination of whether this condition existed, as with all the other conditions, is an empirical judgment. For example, in the weakened-cable hypothetical, C’s weakening of the cable was considered to be a duplicative cause when the cable broke at the weakened point. If the cable had broken instead at some other point, our empirical evaluation would be that the potential causal effect of C’s weakening of the cable was preempted by the existence of this other weaker point in the cable. This other weaker point prevented the cable from staying together long enough for C’s weakened point to have any effect. In those circumstances, C’s weakening of the cable would not be a necessary element of any sufficient set of actual antecedent conditions.
The key to the overdetermined-causation cases, therefore, is the distinction between duplicative and preemptive causation. In each case, an empirical judgment must be made: was the tortious aspect of the defendant’s conduct a necessary element in a set of actual antecedent conditions that was sufficient for the occurrence of the injury, or was it not a necessary member of any actually sufficient set because its potential effects were preempted by other actual conditions outside the set?
In the merged-fires cases or the noisy-motorcycles case, we believe that each factor duplicates or reinforces the effects of the other factor, rather than preempting those effects—that is, that there is more than one sufficient cause. In the shooting case, however, we believe that there was only one sufficient cause (the shooting), which preempted the effects of the other potential cause (the poisoning) and thereby prevented it from being a necessary member of an actually sufficient set. We would believe otherwise if medical experts testified that the effects of the poison combined with the effects of the shooting to cause the victim’s death, although either alone would have been sufficient. The critical issue is whether one factor completely preempted the potential effects of the other factor, so that there was only one sufficient (preemptive) cause in the actual circumstances, or whether each factor was a necessary part of a different (but overlapping) actually sufficient set, in which case there was more than one sufficient (duplicative) cause.
Hart and Honore submerge this critical issue in their discussion of the overdetermined-causation cases. They construct a typology that first divides the cases into those involving “additional causes” and those involving “alternative causes.” The alternative-cause category is meant to include those cases in which there was a potential alternative cause which never occurred. Examples include the cases where the defendant assets that someone else would have shot or robbed the plaintiff if he had not. However, Hart and Honore also include a bridge-delay case in which there was an actual second bridge that would have delayed the plaintiff’s boat even if the first bridge had not. It is misleading to speak of these cases as alternative-cause cases. As Hart and Honore clearly indicate, the alternative cause was not a cause. It was a preempted potential cause, best referred to as a “preempted condition.” The category is a subset of the preemptive-causation cases.
Their additional-cause category is subdivided into three subcategories. The “combinatory” or “reinforcing” cause subcategory, however, is the only one that actually involves additional (duplicative) causes. The other two subcategories are subsets of the preemptive-causation cases, where again it is misleading to refer to the preempted condition as an additional cause. The “neutralizing” cause subcategory covers situations in which the effective cause prevents an alternative active causal process from being completed. For example, a fire approaching a house is quenched by a flood which destroys the house, or a poison victim is killed by a bullet before the poison kills him. The “overtaking” cause subcategory originally was limited to situations in which a subsequent actual injury would have caused the same damage as the initial injury: for example, two successive injuries, each of which would have been sufficient to disable the victim totally. However, the subcategory has been expanded in the second edition to encompass situations in which the effective cause frustrates an active causal process, so that the subcategory now overlaps the “neutralizing” cause subcategory.
Perhaps as a result of their confusing typology, Hart and Honore lose sight of the basic concept of causation embodied in the NESS test. In the double-bridge and successive-injury cases, for example, the defendant’s tortious conduct was a (preemptive) cause of the boat’s delay in the double-bridge case and a (preemptive) cause of the victim’s loss of a limb and resulting total disability in the successive-injury case. But Hart and Honore claim that the tortious conduct was not a cause of the victim’s economic loss in either case, since the victim would have suffered the economic loss anyway as a result of the second bridge or the second injury, respectively.
This causal argument, however, is based on the but-for test rather than the NESS test. In each case, the defendant’s tortious conduct was a necessary element of a set of actual antecedent conditions that did not include the subsequent condition (the second bridge or the second injury) and was sufficient for the occurrence of the economic loss. The existence of the subsequent condition did not prevent this set from being sufficient to produce the economic loss. On the other hand, neither the second bridge nor the second injury was a necessary element of any set of actual antecedent conditions that was sufficient for the occurrence of the loss. The second bridge will cause a delay only if the boat reaches it, but the boat did not reach it. The second injury will cause total disability and resulting economic loss only if the victim is not already totally disabled, but this also was not one of the actual conditions. In each instance, the defendant’s tortious act is a preemptive cause of the injury and the resulting economic loss, and the subsequent preempted condition is not a cause of the economic loss.
4. Distinguishing the Damages Issue: The Successive-Injury and Overwhelming-Force Cases
The successive-injury cases have engendered much debate and confusion, particularly in the Commonwealth countries, where the legal community seems unable to free itself from the but-for concept of causation. The causal situation is clear in these cases. The first injury caused the economic loss; the second did not. The issue is not causal. It is a proximate-cause issue of policy or principle that is most appropriately placed under the heading of damages, and it also arises in the duplicative-causation cases. The issue is whether a defendant who has tortuously caused injury to the plaintiff nevertheless should be absolved from liability if the injury would have occurred anyway as a result of independent duplicative or preempted conditions.
Courts generally absolve the defendant from liability if he proves that the injury would have occurred anyway as a result of independent non-tortious conditions. In such a case, the plaintiff’s corrective-justice claim—that he would not have been injured if not for the tortious conduct of others—fails. On the other hand, if the duplicative or preempted conditions also resulted from tortious conduct, the plaintiff’s corrective-justice claim is intact. Nevertheless, it may seem unfair to hold a defendant liable for the entire injury if his contribution to the injury was relatively minor compared to the other contributing conditions. But this proximate-cause problem has been greatly lessened by the recent widespread liberalization of the rules governing contribution among defendants. Therefore, once the plaintiff has established that the tortious aspect of a certain defendant’s conduct contributed to the injury, many courts shift the burden to the defendant to establish that (1) the injury would have occurred anyway as a result of independent non-tortious conditions, (2) he contributed to only a part of the injury, or (3) he is entitled to contribution from the other defendants based on relative tortious contribution.
The causal issue is almost always confused with the policy-laden damages issue in the overwhelming-force cases involving passive conditions. When an overwhelming force combines with an active condition, the courts are less likely to confuse the two issues. Thus, in the merged-fires cases, the courts generally recognize that the defendant’s smaller fire that combined with a much large fire nevertheless contributed to the injury. If the defendant avoids liability, it is not due to a lack of causal contribution but rather due to non-causal limitations. For example, the defendant usually can avoid liability if he proves that the other fire was independently sufficient and of non-tortious origin, or perhaps even if it was also of tortious origin if it was so overwhelming as to make the defendant’s contribution relatively insignificant. On the other hand, the defendant is unlikely to escape liability even though his contribution was a very small part of the total cause if it was necessary for the consequence or, although unnecessary, was combined with a large number of similarly small contributions, as in the pollution cases.
When the overwhelming force combines with a passive condition, however, most courts and commentators tend to fall back on the but-for test and erroneously deny causal contribution. For example, the courts deny that the defendant’s negligent failure to construct an adequate dam or to keep runoff pipes free of debris was a cause of flooding that would have occurred given a normal storm, if the actual storm was an extraordinary one that would have caused flooding even if the defendant had not been negligent. Similarly, they have stated that the defendant’s negligent failure to remove a rotten pole is not a cause of injury when the pole is knocked down by a car that hits it with such force that it would have been knocked down even if it were not rotten.
These are overdetermined-causation cases that are entirely analogous to the merged-fires cases and the weakened-cable case. Thus, if the rotten pole broke at its weak point, the weak condition clearly contributed to the injury. It was a necessary element of a sufficient set of actual antecedent conditions that included an impact with at least enough force to knock down a rotten pole. The sufficiency of the set was not affected by the fact that the impact had a greater force, unless the impact knocked the pole over in its entirety rather than breaking it at its weak point. Similarly, the failure to remove debris from a dam’s runoff pipes or to build it high enough to prevent flooding during a normal storm is a duplicative cause of flooding that occurs during an extraordinary storm. The unremoved debris or inadequate height is a necessary element in a sufficient set of actual antecedent conditions that includes an at least normal storm, and the sufficiency of this set is not affected by the fact that the storm was larger than normal.
A few courts have recognized that the defendant’s tortious conduct contributed to the injury in these passive-condition cases. Indeed, some courts have held the defendant liable even when the injury would have occurred anyway as a result of independently sufficient non-tortious conditions. However, if the non-causal policy limitations adopted in the merged-fires and successive-injury cases are followed, the defendant should be able to avoid liability in such circumstances. These policy limitations, rather than the false denial of causation, explain the ultimate result in those cases in which liability is denied because the injury would have occurred anyway due to the extraordinary force of a storm.
Conversely, given the usual policy limitations, the defendant should not escape liability when the duplicative or preempted condition was also of tortious origin—for example, when the defendant’s rotten pole is knocked down by a negligent driver and an innocent third party is injured. This case is the same as a merged-fires case in which the defendant’s insufficient fire joins with an independently sufficient fire, also of tortious origin. In each case, both conditions are tortious duplicative causes of the injury, and liability should be imposed jointly on both toreadors with a right of contribution.
5. Theft, Nonuse, or Misuse of Defective or Missing Safety Devices
Some of the most difficult overdetermined-causation cases are the preemptive-causation cases involving theft, nonuse, or misuse of defective or missing safety devices. A familiar example is the case in which C negligently failed to discover and repair defective brakes in a car that he rented to D, and D negligently failed to try to use the brakes to avoid running into P. It is assumed that the injury to P would have been avoided if and only if C had repaired the brakes and D had tried to use them. As we saw above, Green asserts that C’s conduct as a whole and D’s conduct as a whole were each causes of the injury, but that only C should be held liable. Becht, Miller, Prosser, and Fleming assert that neither C’s negligence nor D’s negligence was a cause of the injury, but that both C and D should be held liable.
Under the NESS test, it is clear that D’s negligence was a preemptive cause of P’s injury, and that C’s negligence did not contribute to the injury. D’s failure to try to use the brakes was necessary for the sufficiency of a set of actual antecedent conditions that did not include C’s failure to repair the brakes, and the sufficiency of this set was not affected by C’s failure to repair the brakes. A failure to try to use brakes will have a negative causal effect whether or not the brakes are defective. On the other hand, C’s failure to repair the brakes was not a necessary element of any set of antecedent actual conditions that was sufficient for the occurrence of the injury. Defective brakes will have an actual causal effect only if someone tries to use them, but that was not an actual condition here. The potential negative causal effect of C’s failure to repair the brakes was preempted by D’s failure to try to use them.
The same analysis applies in every case involving nonuse or misuse of a missing or defective safety device, unless the actor did not try to use the device because he knew it was missing or defective. For example, failure to provide a fire escape was not a cause of P’s injury if P could not have gotten to the fire escape anyway or would not have tried to get to it even if it existed. Similarly, failure to provide safety equipment to a worker is not a cause of his injury if he would not have used it anyway, and failure to pack a parachute properly is not a cause of death if the deceased never pulled the ripcord to release the parachute.
A somewhat different situation is presented by McLaughlin’s hypothetical in which D empties P’s water keg and refills it with salt before P is dropped into the middle of a desert. C subsequently steals the keg, thinking that it contains water, and P dies of thirst. This case is different from the previous cases because it is assumed that P would have used the water (“safety device”) if it had been available. D’s emptying the keg made the water unavailable and was a preemptive cause of P’s death. C’s theft of the keg was not a cause of P’s death. Its potential effect (making the water unavailable) depended on the keg’s having water in it when it was stolen, but that was not an actual condition.
Hart and Honore modify the facts by having D poison the water in the keg rather than replacing it with salt. They conclude that neither C nor D was a cause of P’s death, but only because they equate causing death with shortening life and note that P would have died sooner by poisoning if C had not stolen the keg. As Becht and Miller point out, and as a NESS analysis demonstrates, the lack of water (fluid) caused the death, and it is irrelevant that P would have died sooner if he had drunk the poisoned water. He in fact did not drink the poisoned water, because C stole it. C’s theft caused P’s death and preempted the potential causal effect of D’s poisoning the water.
It should be clear by now that the NESS test not only resolves but also clarifies and illuminates the causal issues in the problematic causation cases that have plagued tort scholars for generations. It does so because it is not just a test for causation, but is itself the meaning of causation. When there is no overdetermined-causation problem—that is, when there is only one actual or hypothetical sufficient set of conditions for a particular event—the NESS test collapses into the simple, traditional but-for test. But the concept of causation is much subtler and complex than the but-for test. Thus, whenever the but-for test is not satisfied, the factfinder must utilize this more complex notion of causation, with its often subtle distinction between actual sufficiency and mere apparent (preempted) sufficiency, before the causal inquiry can be concluded.
Excerpted from “Causation in Tort Law,” California Law Review 73:6 (December 1985), pp. 1775–1803
Reprinted with permission of the publisher
Maimonides: Laws of the Negligent Killer
Laws of Murder and Preservation of Life, Chapter 5
1. Whenever a person kills unintentionally, he should be exiled from the city in which he killed, to a city of refuge. It is a positive mitzvah to exile him, as implied by Numbers 35:25: “He shall dwell there until the death of the High Priest.”
The court is admonished not to accept a ransom from the killer to enable him to remain in his city, as Ibid., 32 states: “You shall not accept a ransom so that he will not have to flee to his city of refuge.” . . .
7. At the outset, both a person who killed unintentionally and one who killed intentionally should flee to a city of refuge. The court in the city in which the killing took place sends for the killer and brings him back to that city, as ibid.:12 states: “And the elders of his city shall send and take him from there.”
If the killer is condemned to execution, he should be executed, as ibid. continues: “And they shall give him to the hand of the blood redeemer.” If a person is absolved, he should be released, as Numbers 35:25 states: “And the congregation shall save the killer from the hand of the blood redeemer.” And if the killer is sentenced to exile, he should be returned to his previous place, as ibid. continues: “And the congregation shall return him to his city of refuge.”
8. When he is returned to his city of refuge, he is given two Torah sages to accompany him, lest the blood redeemer attempt to kill him on the way. They should tell him: “Do not deal with him in the manner of those who shed blood. It was unintentional that this happened.”
9. When a blood redeemer slays a person who killed unintentionally outside the Sabbath limits of his city of refuge, he is not held liable, as Deuteronomy 19:6 states: “He is not judged as liable to be executed.”
10. The above applies whether he kills him on the road before he enters his city of refuge or if he kills him when returning together with the two who are guarding him. If he enters his city of refuge and intentionally departs beyond its Sabbath boundaries, he has granted license for his life to be taken. The blood redeemer is permitted to kill him. And if another person kills him, that other person is not liable, as Numbers 35:27 states: “There is no liability for his blood.”
11. If the killer leaves his city of refuge unintentionally, whoever slays him—whether the blood redeemer or another person—should be exiled. If the killer is slain within the Sabbath limits of the city of refuge, the one who slayed him should be executed.
12. The altar in the Temple serves as a haven for killers. This is derived from Exodus 21:14, which states with regard to a person who kills intentionally: “You shall take him from My altar to die.” One can derive from this, that one who kills unintentionally should not be killed at the altar.
Thus, if a person kills unintentionally and takes refuge at the altar, and the blood redeemer kills him there, he should be executed as if he killed him in a city of refuge.
13. What serves as a haven is only the top of the altar in the Temple. Moreover, it serves as a haven only for a priest who is in the midst of sacrificial worship. For a person other than a priest, a priest who is not involved in the sacrificial worship, or a priest who was involved in the sacrificial worship but was near the altar or holding on to its horns, the altar does not serve as a haven.
14. If someone takes refuge on the altar, he is not left there. Instead, he is given guards and taken to a city of refuge.
When does the above apply? When one is obligated to be exiled. If, however, a person feared that a king will have him executed as is the king’s authority, or that the court will execute him as an immediate directive, and fled to the altar and held on to it, he should be saved.
This applies even if he is a commoner. He should not be taken from the altar to die unless he was sentenced to death because of the testimony of witnesses who delivered a warning, as is always required with regard to those executed by the court.
Laws of Murder and Preservation of Life, Chapter 6
1. There are three categories of unintentional killers.
2. There is a person who kills unintentionally, without at all knowing that this will be the consequence of his actions. Concerning such a person, Exodus 21:13 says: “Who did not lay in ambush.” The law applying to such a person is that he should be exiled to a city of refuge, as we have explained in the previous chapter.
3. There is a person who kills unintentionally, whose acts resemble those caused by forces beyond his control—i.e., that the death will be caused by an extraordinary phenomenon that does not commonly occur. Such a person is not liable to be exiled, and if he is slain by the blood redeemer, the blood redeemer should be executed for killing him.
4. There is a person who kills unintentionally, whose acts resemble those willfully perpetrated—e.g., they involve negligence or that care should have been taken with regard to a certain factor and it was not. Such a person is not sentenced to exile, because his sin is very severe and exile cannot bring him atonement, nor do the cities of refuge served as a haven for him. For they serve as a haven only for those obligated to be exiled. Therefore, if the blood redeemer finds this killer anywhere and slays him, he is not liable.
5. What should such a person do? Sit and protect himself from the blood redeemer.
Similarly, if the blood redeemer slays any of the murderers whose acts were observed by only one witness, or who were not given a warning or the like, the blood redeemer is not liable for execution. Killing such individuals should not be considered more severe than killing a person who killed unintentionally.
6. What does the above imply? When a person throws a stone into the public domain and it causes death or he tears down his wall into the public domain, and a stone falls and causes death—whether he tears down the wall during the day or during the night—he is considered to be close to having acted intentionally. A city of refuge does not serve as a haven for him. For he should have checked the surroundings and then thrown the stone or torn down the wall.
7. The following rules apply if a person tears down a wall into a garbage dump at night. If it is likely that people are there, he is considered to be close to having acted intentionally, and a city of refuge does not serve as a haven for him. If people are never found there, the death is considered close to having been caused by forces beyond his control, and he is not liable for exile.
8. Different rules apply if people would use a garbage dump to relieve themselves at night, but would not use it for this purpose during the daytime. If it happened that a person sat there during the day, and he was killed by a stone that came from a person tearing down his wall, the person who tore down his wall should be exiled.
9. If after the stone began to fall, the person came and sat down, and the stone struck him and caused his death, the person who tore down his wall is not liable to be exiled.
10. Similarly, if a person threw a stone into the public domain, and after the stone left his hand, the victim stuck his head out from a window and was struck by it, the person who threw the stone is not liable for exile. This is derived from Deuteronomy 19:5, which states: “the iron slips from the wood and finds his fellow.” This excludes an instance when the victim causes himself to be found by the iron or other object that causes death.
When a person who hates the victim kills unintentionally, the city of refuge does not serve as a haven for him. This is implied by Numbers 35:23, which states that a person who is exiled: “is not the victim’s enemy.” We operate under the presumption that one who is an enemy is close to having acted willfully.
Who is considered to be an enemy? A person who did not speak to the victim for at least three days because of animosity.
Similarly, all the following individuals are considered close to having acted willfully, and a city of refuge does not serve as a haven for them:
a) a person who entered an intersection holding an open knife in his hand without realizing that the victim was approaching from the other side and unintentionally stabbed him, causing his death;
b) a person who unintentionally pushed a colleague to his death with his body and not with his hands;
c) a person who intended to throw a stone that could kill two cubits, and instead threw it four;
d) a person who thought that it was permitted to kill;
e) a person who intended to kill one person and instead killed another. This applies even if he intended to kill a gentile or an animal and instead killed a Jew.
11. When a person enters a courtyard of a homeowner without permission, and the homeowner kills him unintentionally, the homeowner is not liable to be exiled as can be inferred from Deuteronomy 19:5, which, when describing a person who must be exiled speaks of one: “Who encounters his colleague in the forest.” Our Sages commented: A forest is a place that the victim has the right to enter. Similarly, in all such places, and only in such places, is a killer liable to be exiled.
Therefore, if a person enters a carpenter’s shop without permission, and a block of wood flies forth and strikes him in the face and kills him, and he dies, the carpenter is not liable to be exiled. If he entered with permission, the carpenter should be exiled.
12. When a person was lifting a barrel with a pulley to bring it up to a roof, and the the rope broke, causing it to fall on a colleague, or a person was climbing up a ladder and fell on a colleague and killed him, the person who caused the death is not liable to be exiled. This is considered to be something beyond his control. For this is not something that is likely to happen, but is rather an extraordinary occurrence.
If, by contrast, a person was lowering a barrel with a rope and it fell on a colleague and killed him, he was descending on a ladder and fell on a colleague, or he was shining with a polisher and it fell on a colleague and killed him, the person responsible should be exiled.
This is derived from Numbers 35:23, which states: “And it fell upon him, and he died,” implying that the article must descend in an ordinary manner. An object that descends frequently causes damage. Indeed, it is likely that this will happen, for the nature of a heavy object is to descend downward speedily. Therefore, if the person did not hurry and act appropriately and properly while the object descended, he is responsible and should be exiled. The same applies in other analogous situations.
13. The following rules apply when a butcher was cutting meat and lifted his hands backward while holding a cleaver, and then brought them forward to break a bone, as butchers do. If anyone is killed while he draws the cleaver back—i.e., while he lifts it up in front of him or while he causes it to descend behind him, the butcher is not exiled. If anyone is killed when he brings the cleaver forward—i.e., while he lifts it up behind him or while he causes it to descend in front of him—the butcher should be exiled.
This is the governing principle. Whenever the object that kills is descending, the person responsible should be exiled. If it is not descending, he should not be exiled. Even a descent for the purpose of ascent does not cause the person to be exiled.
14. What is an example of a “descent for the purpose of an ascent”? If a person was ascending on a ladder, and a rung gave way under his feet and fell and caused death, the person climbing is not obligated to be exiled.
Similarly, in the following situations, the death is considered close to having been caused by factors beyond the control of the individuals involved and they are not exiled:
a) a person intended to throw an article in one direction and it went in another direction,
b) a person had a stone in his bosom that he had never been made aware of and when he stood up it fell, or
c) a blind man killed someone unintentionally.
15. If there was a stone in his bosom that he was aware of and he forgot it, and then he stood up, the stone fell and caused death, he is exiled, as implied by Numbers 35:15, which mentions the death taking place “unintentionally.” From the use of that term, we can infer that he knew of the stone’s existence beforehand.
If the iron slips from the axe rebounding from the tree he is chopping, he is not exiled, because this does not come from his own force, but from the effect generated by his force. Thus, it is like a factor that is beyond his control.
Similarly, if a person throws a stone into a date palm to knock down dates, and the dates fall on an infant and kill him, the person who throws the stone is not liable to be exiled, because the infant was killed, not by force that he generated, but from the effect generated by his force. Similar principles apply with regard to other blows brought about by analogous situations.
Translated by Rabbi Eliyahu Touger. Published and copyright by Moznaim Publications.
Available at www.chabad.org/682956
Reprinted with permission of the publisher
