Divisible and Indivisible Injuries ‒ Causation and Assessment of Damages

Moore v. Kyba, 2012 BCCA 361  holds that Indivisible Injury Analysis is applicable for both causation and quantum of damages:



[32] Much judicial ink has been spilled concerning the characterization of multiple injuries as divisible or indivisible, and the impact of that characterization on the determination of causation and assessment of damages in a negligence case.

[33] The legal principles underlying these concepts are clear, but explaining them to a jury “is no easy task” (see Laidlaw v. Couturier, 2010 BCCA 59 (CanLII), 2010 BCCA 59 at para. 40). Nor is their application in varying particular factual contexts always straightforward.

[34] The relevant principles were clearly set out in Athey v. Leonati, 1996 CanLII 183 (SCC), [1996] 3 S.C.R. 458. Their elaboration in Blackwater v. Plint, 2005 SCC 58 (CanLII), 2005 SCC 58, [2005] 3 S.C.R. 3, and by this Court in T.W.N.A. v. Canada (Ministry of Indian Affairs), 2003 BCCA 670 (CanLII), 2003 BCCA 670 at paras. 22-37, B.P.B. v. M.M.B., 2009 BCCA 365 (CanLII), 2009 BCCA 365, Bradley v. Groves, 2010 BCCA 361 (CanLII), 2010 BCCA 361 and Laidlaw are also helpful.

[35] The basic principles at play in this analysis are that a “defendant is not liable for injuries which were not caused by his or her negligence” (Athey at para. 24), and “the defendant need not put the plaintiff in a position better than his or her original position” (Athey at para. 35). These two principles, which deal with the concepts of causation and assessment of damages, were distinguished in Blackwater (at para. 78):

It is important to distinguish between causation as the source of the loss and the rules of damage assessment in tort. The rules of causation consider generally whether “but for” the defendant’s acts, the plaintiff’s damages would have been incurred on a balance of probabilities. Even though there may be several tortious and non-tortious causes of injury, so long as the defendant’s act is a cause of the plaintiff’s damage, the defendant is fully liable for that damage. The rules of damages then consider what the original position of the plaintiff would have been. The governing principle is that the defendant need not put the plaintiff in a better position than his original position and should not compensate the plaintiff for any damages he would have suffered anyway: Athey.

[36] Thus, whether a defendant is liable to a plaintiff for an injury is a matter of causation; the amount of compensation the defendant must pay is a matter of assessment of damages.

[37] The concepts of divisible and indivisible injury are relevant at both stages of the analysis. At the stage of determining causation, the characterization of the plaintiff’s injury or injuries as divisible or indivisible is relevant in determining what the defendant is liable for. As explained in Athey (at paras. 24-25):

The respondents submitted that apportionment is permitted where the injuries caused by two defendants are divisible (for example, one injuring the plaintiff's foot and the other the plaintiff's arm): Fleming, supra, at p. 201. Separation of distinct and divisible injuries is not truly apportionment; it is simply making each defendant liable only for the injury he or she has caused, according to the usual rule. The respondents are correct that separation is also permitted where some of the injuries have tortious causes and some of the injuries have non-tortious causes: Fleming, supra, at p. 202. Again, such cases merely recognize that the defendant is not liable for injuries which were not caused by his or her negligence.

In the present case, there is a single indivisible injury, the disc herniation, so division is neither possible nor appropriate. The disc herniation and its consequences are one injury, and any defendant found to have negligently caused or contributed to the injury will be fully liable for it.
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[38] In this case, in determining causation, the jury had to determine whether the appellant caused injury to the respondent, and if so, whether the rotator cuff injury, the interscapular pain, and the bicep tear were divisible injuries or an indivisible injury. If they were divisible, the appellant could only be found to be liable for the interscapular pain caused by the motor vehicle accident. If they were indivisible, the appellant would be liable for that indivisible injury.

[39] The appellant takes no issue with the trial judge’s instruction to the jury concerning divisible and indivisible injury in the context of determining causation.

[40] The appellant argued at trial that no injuries were caused by the motor vehicle accident and he was not liable for any of the respondent’s claimed losses. The jury clearly rejected that argument.

[41] At the stage of assessment of damages, the question is what compensation the plaintiff is entitled to receive from the defendant.

[42] If the injury is divisible, then the plaintiff is entitled to be compensated for the injury caused by the defendant. In this case, if the interscapular pain was a divisible injury, then the respondent was entitled to compensation for his loss flowing from that injury.

[43] If the injury is indivisible, then the plaintiff is entitled to be compensated for the loss flowing from the indivisible injury. However, if the plaintiff had a pre-existing condition and there was a measurable risk that that condition would have resulted in a loss anyway, then that pre-existing risk of loss is taken into account in assessing the damages flowing from the defendant’s negligence. This principle is called the “crumbling skull” rule. As explained in Athey (at para. 35): “This is consistent with the general rule that the plaintiff must be returned to the position he would have been in, with all of its attendant risks and shortcomings, and not a better position.”