Establishing Causation in a Motor Vehicle Accident case
Reasons for judgment were released today in the case of Chappell v. Loyie. This case involved an assessment of damages for a plaintiff after he was injured when his motorcycle was struck by a left turning vehicle. The plaintiff did not suffer a serious head injury or any broken bones but the injuries he did have were quite significant and complex, partly due to the fact that he had some pre existing conditions that became seriously symptomatic at various times following the accident. The accident occurred when the defendant turned left in front of the plaintiff. ICBC admitted liability on her behalf. This case gave the court an opportunity to provide a summary of the difficult area of the law of causation. To establish causation a plaintiff must prove on a balance of probabilities that a defendant caused or contributed to his injury. In a case like Chappell that is a difficult task. Madam Justice Fisher described the law applicable to determining causation in situations involving pre existing conditions as follows:
 As the court said in Blackwater, a plaintiff is only to be restored to his original position, and not a better position. A defendant is not required to compensate a plaintiff for any debilitating effects arising from a pre-existing condition that the plaintiff wouldhave experienced anyway, and if there is a measurable risk that the pre-existing condition would have detrimentally affected the plaintiff in the future, regardless of the defendant’s negligence, this is to be taken into account in reducing the overall award…In addition, damages cuased by other non-tortious causes that occur after the defendant’s wrongful act must be taken into account…This is referred to as the “crumbling skull” doctrine. It is important to note that any reduction made to take these factors into account does not reduce the damages; it simply awards the damages which the law allows…
 In addition, a tortfeasor is liable for a plaintiff’s injuries even if the injuries are unexpectedly severe owing to a pre-existing condition. As the court said in Athey, at para. 34, the tortfeasor must take the victim as he finds him, and is liable even though the plaintiff’s losses are more dramatic than they would be for the average person. This is known as the “think skull rule”.
 There has been some confusion in the law with respect to these labels…the court clarified this at para. 30 by stating that the “simple idea” expressed in Athey, was clear and direct and “both latent and active pre-existing conditions muts be considered in assessing the plaintiff’s original position.” At para. 48:
…Whether manifest or not, a weakness inherent in a plaintiff that might realistically cause or contribute to the loss claimed regardless of the tort is relevant to the assessment of damages. It is a contingency that should be accounted for in the award. Moreover, such a contingency does not have to be proven to a certainty. Rather, it should be given weight according to its relative likelihood.
 Hypothetical and future events – how the plaintiff’s life would have gone without the tortious injury – need not be proven on a balance of
probabilities. They are given weight according to their relative likelihood, or the probability of their occurrence. A future or hypothetical possibility is to be taken into account “as long as it is a real and substantial possibility and not mere speculation”.
This decision provides not only an excellent summary of the law of causation but also an excellent example of how that law is applied to a situation involving complex facts. With causation, each case is decided on its facts and the evidence that is presented with respect to the plaintiff’s condition prior to the accident. Illustrations of how this is applied however, can assist in understanding this complex legal principle.