This excerpt is the complete text of Part 10 of  “Black Holes, Aether”. The footnotes have been renumbered. Full cites added where needed to make the excerpt as self-contained as plausible.

10.       EXAMPLES BY CATEGORY

I outline, in this Part, how factual causation law is to be applied after the judge or jury has made the required findings of fact on the issue of whether the evidence permits the conclusion that, on the balance of probability, a wrongdoer’s negligence was or was not a part of the set of events that was a factual cause of the injury.

The examples are divided into two categories. The first category includes all instances in which the evidence is sufficient for the court to make a valid decision, on the balance of probability, that the defendant’s negligence is or is not a factual cause. The second category includes all instances in which the evidence is not sufficient for the court to make that decision, but that result does not require the dismissal of the action. Each of the two categories has four sub-categories, determined by whether there is more than one causal candidate and, if so, whether any of the other causal candidates would be causes which were never actionable. In all of the categories, the existence of multiple negligent causal candidates is the result of the existence of multiple tortfeasors, not merely one tortfeasor who has committed multiple negligent acts.

(a)        Instances where the evidence is sufficient for the causal connection decision to be made

In the following four categories, which subsume all of the variations that could occur, the evidence is sufficient for the court to decide the causal status of each of the causal candidates on the basis of the applicable standard of proof. That is, the evidence is sufficient for the court to find that the party with the burden of proof on the issue has satisfied the burden, or has failed to satisfy the burden.

(1)        No other causal candidate

This is the most common situation. The only question the court has to decide is if the evidence is or is not sufficient to satisfy the burden of proof which is currently the balance of probability. If the plaintiff has the burden of proof, as is usually the case, the action fails if the court finds that evidence is not sufficient. Otherwise, the court proceeds to the other issues if the evidence is sufficient.[1] This was the situation in Clements, according to the Supreme Court. “This is a simple single-defendant case: the only issue was whether ‘but for’ the defendant’s negligent conduct, the injury would have been sustained.”^[2]

In those instances where there is a reverse onus, so that the onus is on the defendant to show no causal connection (to the required standard of proof) between the injury and the defendant’s negligence, the action proceeds if the evidence is not sufficient to meet that standard.[3]

(2)        One or more other causal candidates all of which were never actionable even if wrongful

The plaintiff alleges the defendant’s negligence caused injury Q. The defendant alleges that there is something which occurred before the defendant’s negligence, or something which occurred as part of the incident that resulted in the injury,[4] or something after but before the trial, which is sufficient to have caused the plaintiff’s injury even if the defendant had not been negligent.[5]

The plaintiff establishes factual causation If the evidence is sufficient to show that the negligence was necessary, on the balance of probability, for the injury to have occurred, and the defendant is not able to establish to establish the causal status of the other causal candidates on the balance of probability. The situation is equivalent to example (1) above.

The negligence is a factual cause if the negligence and the never-actionable causal candidate(s) are cumulatively necessary – are all necessary in combination – for the injury to have occurred.[6] The action continues so that the other issues may be determined.

The negligence is a factual cause of the injury if the evidence shows that the negligence and any of these other events would be sufficient, on the balance of probability, to cause the injury the plaintiff sues for, even if the negligence had not occurred. However, in this case the other never-actionable cause is also a sufficient cause. The action fails as the plaintiff has not established that the negligence caused any compensable damage. The negligence did not make any difference. The plaintiff’s position is the same as it would have been even if the negligence had not occurred. The plaintiff is not entitled to be put in a better position than the plaintiff would have been if the negligence had not occurred. There has been no change in the plaintiff’s position as a result of the negligence, so there is no actionable injury.[7]

This category subsumes all instances of so-called indivisible injury[8] where at least one of the other separately sufficient causal candidates was never actionable at all. Recall that “[d]ivisible injuries are those capable of being separated out and having their damages assessed independently. Indivisible injuries are those that cannot be separated or have liability attributed to the constituent causes.”^[9]

(3)        One or more other causal candidates all of which were once actionable even if one or more are no longer actionable

The negligence is a factual cause if the evidence establishes, on the balance of probability, that the negligence is sufficient to have caused the injury.

It does not matter if there are other causal candidates which were once actionable, regardless of whether the evidence shows the other causal candidate(s) are cumulatively necessary in combination with the defendant’s negligence; or, that one of more of the other causal candidates is also sufficient to cause the injury even without the negligence. In either case, the existence of this other negligent cause is not a defence. In both cases, this is an application and consequence of the long-standing, common law, rule that concurrent tortfeasors are jointly liable for damages caused by their negligence.[10] Tortfeasors are concurrent tortfeasors where there negligence causes the same injury. The causal situation occurs whether the negligence of the multiple is cumulatively necessary or separately sufficient.[11] The decision to treat the instances of multiple cumulative and multiple separately sufficient negligent causes the same, as between plaintiff and wrongdoer, is a policy decision.[12]

This category subsumes all instances of so-called indivisible injury[13] where all of the causal candidates are or were tortious and actionable but the court decides that the evidence does not permit a valid decision, on the balance of probability, as to whether the injury was caused by all of the causal candidates or any or of them, or group of the them fewer than all.

(4)        One or more of the other causal candidates were never actionable even if wrongful

If the other causal candidates are, at most, cumulatively necessary with the negligence of the defendant, then that negligence is a factual cause. This is a necessary corollary of the principle that the negligence is a factual cause where those other causal candidates would be actionable.[14] There is no valid basis, so long as the liability of concurrent tortfeasors is joint (solidary), for treating this situation as equivalent to the situation where the other causal candidates were never actionable.

The same rule should apply where the evidence establishes that any one of the other never-actionable, even though wrongful, causal candidates is separately sufficient.[15]

(b)       Instances where the evidence is NOT sufficient for the causal connection decision to be made on the balance of probability but that does not require the dismissal of the action

This category includes those cases where the facts and the quality of evidence produce the situation capable of triggering the material contribution to injury doctrine. In those case, the evidence does not show that any one of the multiple, once actionable, negligent events, or any combination of them fewer than all, is sufficient, on the balance of probability to have caused the injury.

In addition, the evidence does not show, on the balance of probability, that the negligence of the defendant, on its own or in combination with some never-actionable event, was not a cause.[16]

Again, all variations will fall into one of the four categories.

(1)        No other causal candidate

The action fails because the plaintiff has not satisfied the onus of proof and, at present, the material contribution to injury doctrine does not apply to instances where there is only one potential causal candidate.[17]

(2)        One or more other causal candidates all of which were never actionable even if wrongful

The action fails, so long as it is not a class action,[18] because the plaintiff has not satisfied the onus of proof and, at present, in Canada, the material contribution to injury doctrine does not apply to instances where there is only one potential negligent causal candidate.[19]

This restriction to instances having two more tortfeasors not the law in the United Kingdom: see Barker v. Corus,[20] and Sienkiewicz v. Grief (UK) Ltd.[21] In addition, there is nothing in the material contribution to risk doctrine as explained in Resurfice or Clements that requires this restriction. It was declared by the Supreme Court in Clements without valid explanation. The Court stated that Sienkiewicz was “the only case to apply a material contribution to risk approach to a single tortfeasor”,[22] the Court, surprisingly, failed to mention that one of the relevant causal candidates in Barker v. Corus was the contributory fault of the injured person. There is no necessary logical distinction between an instance which has two or more negligent causal candidates and one never-actionable (whether innocent or wrongful) causal candidate and an instance which has only one negligent causal candidate. The House of Lords recognized that in Sienkiewicz. It is the basis upon which Barker v. Corus was applied in Sienkiewicz. In the result, the Clements requirement, outside of class actions (perhaps) that there be two or more negligent causal candidates is entirely a matter of policy.

A possible justification may be seen in the following. Under current law, the plaintiff will lose if the evidence shows, on the balance of probability, that the negligence and the never-actionable condition are both separately sufficient causes. Why, then, should a plaintiff succeed if the evidence is not sufficient to show that either is or is not a probable cause? If a plaintiff is to succeed in such cases, there must be some valid reason in policy. Clements implies, in para. 44, that such a reason may exist in class actions.

The result may be different in class actions. Clements states:

This is not to say that new situations will not raise new considerations. I leave for another day, for example, the scenario that might arise in mass toxic tort litigation with multiple plaintiffs, where it is established statistically that the defendant’s acts induced an injury on some members of the group, but it is impossible to know which ones.[23]

The Court did not explain why injured persons in mass injury situations ought to be treated differently from injured persons where, fortunately, no other person may have been injured by the negligence; or, at least, there is no plausible evidence to support that allegation.

Any distinction will be based on what is perceived to be valid policy considerations. It is implicit in the Court’s specific reference to the possibility of a different result in mass injury cases that the importance of providing content to the defendant’s duty of care will play a part in the ultimate decision.[24]

(3)        One or more other causal candidates all of which were once actionable even if one or more are no longer actionable

This is the situation that Clements states contains the facts that may make the material contribution to risk doctrine applicable.

       Exceptionally, a plaintiff may succeed by showing that the defendant’s conduct materially contributed to risk of the plaintiff’s injury, where (a) the plaintiff has established that her loss would not have occurred “but for” the negligence of two or more tortfeasors, each possibly in fact responsible for the loss; and (b) the plaintiff, through no fault of her own, is unable to show that any one of the possible tortfeasors in fact was the necessary or “but for” cause of her injury, because each can point to one another as the possible “but for” cause of the injury, defeating a finding of causation on a balance of probabilities against anyone.[25]

The Supreme Court added in applying this rule to the facts of Clements:

The special conditions that permit resort to a material contribution approach were not present in this case. This is not a case where we know that the loss would not have occurred “but for” the negligence of two or more possible tortfeasors, but the plaintiff cannot establish on a balance of probabilities which negligent actor or actors caused the injury. This is a simple single-defendant case: the only issue was whether “but for” the defendant’s negligent conduct, the injury would have been sustained.[26]

(4)        One or more of the other causal candidates were never actionable even if wrongful

This instance contains the problem of why the plaintiff should succeed in instances of insufficient evidence. That is, the question is why the plaintiff should succeed in an instance where the evidence is not sufficient to permit a valid conclusion on the balance of probability as to whether any of the causal candidates are, or are not, probable causes, where the plaintiff would not succeed if the evidence showed that the negligence and a never actionable cause were separately sufficient. This problem was discussed in category (ii)(2) above.

c.         Conclusion

The Supreme Court of Canada’s seeming insistence, highlighted in Clements, that the meaning of factual causation is captured by the but-for test is wrong. Borrowing a phrase an Ontario Court of Appeal decision, where the phrase was used in a different context – to describe a decision of a judge lower in the Ontario judicial pecking order – the belief “fails the reality test”.[27] As discussed, there are instances of factual causation which cannot be identified by the but-for test. These instances cannot be identified by the but-for test because the causal relationship between cause and consequence is not based on necessity. There are instances of factual causation where there is sufficient evidence to identify what amounts to multiple but-for causal relationships, in the sense that each of the identified causal relationships would be a but-for relationship if none of the other identified causal relationships existed. A but-for causal relationship is, by definition, a sufficient causal relationship. What these instances of seemingly multiple but-for causal relationships have is multiple sufficient causes to which, by definition, the but-for test as defined by Canadian law cannot be validly applied.