COURT CASES on CRUMBLING SKULL DOCTRINE
“Crumbling Skull” situations arise where where the victim has a condition which is accelerated by the tortfeasor’s actions. If there is a measurable risk that the victim would have eventually suffered from the condition in question anyways, then there can be a reduction in the amount awarded to account for this.the victim is already in a fragile or susceptible state, or has a latent or inherent weakness or condition.
Crumbling Skull situations are not to be confused with “Thin Skull” situations, which arise where the victim is already in a fragile or susceptible state, or has a latent or inherent weakness or condition, and where the tortious conduct of the Defendant causes injuries that a person of normal health would not have suffered. The tortfeasor “takes his victim as he finds him”, and cannot avoid liability for serious injuries that an otherwise normal and healthy person would not have suffered.
Perhaps the best way to make the distinction is that in a thin skull situation, the “skull” is in a stable condition, and would have remained so, without the accident. In a crumbling skull situation, the “skull” was not in a stable condition, but rather was in a state of continuing deterioration, which the accident merely accelerated.
In Booth v Gartner, a deduction of 25% was made for a Plaintiff suffering from degenerative disease, with the court noting:
 According to Dr. Vallentyne, degenerative changes take years to develop and he found it was probable that the plaintiff had degenerative changes of her lower lumbar facet joints prior to the 2007 motor vehicle accident. He concluded that “[g]iven that the degeneration is severe at two levels, it is likely that Ms. Booth would have been troubled by low back pain and stiffness at sometime in the future absent the 2007 MVA.”
 I am satisfied that 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, and I must take that into account in reducing the overall award.
 The principle to be applied is found in Zaruk v. Simpson et al., 2003 BCSC 1748 (CanLII), 2003 BCSC 1748, 22 B.C.L.R. (4th) 43 [Zaruk]. There the plaintiff had suffered a soft-tissue injury but some of her symptoms by the time of trial were consistent with degenerative changes. The Court was not satisfied that the general condition would have become symptomatic between the date of the accident and the date of trial, but concluded at para. 40, that there was a measurable risk that it would have become symptomatic in the future:
 However, application of the crumbling skull doctrine may not result in the same reduction for past losses as future losses. Past losses must be assessed on the basis of a balance of probabilities. “Once the burden of proof is met, causation must be accepted as a certainty,” [Athey v. Leonati, 1996 CanLII 183 (SCC),  3 S.C.R. 458] ¶ 30). But for the assessment of future losses, “[a] future or hypothetical possibility will be taken into consideration as long as it is a real and substantial possibility and not mere speculation,” (Athey ¶ 27)
 Because the plaintiff’s degenerative condition was described by Dr. Vallentyne as “severe bilateral degeneration”, I am of the view that a large deduction is appropriate in this case and I find an appropriate deduction for non-pecuniary damages is 25% and for future care damages, 30%.
In Gohringer v Hernandez-Lazo, the Court discussed the crumbling skull doctrine.
 It is trite law that the general purpose in assessing damages is to restore the plaintiff to their original, or pre-accident, position. Through an award of damages a plaintiff is entitled to be restored to his or her original position, but they are not entitled to be placed in a better position: Athey v. Leonati, 1996 CanLII 183 (SCC),  3 S.C.R. 458 at para. 32, 140 D.L.R. (4th) 235. Generally speaking, this requires the court to determine the plaintiff’s original position and position subsequent to the negligent act, and award damages to reflect the difference: Athey at para. 32; Barnes v. Richardson, 2008 BCSC 1349 (CanLII), 2008 BCSC 1349 at para. 84. In situations where the plaintiff has a pre-existing condition the thin skull or crumbling skull rule must inform the court’s assessment of damages.
 In a thin skull situation, the plaintiff’s pre-existing condition has not manifested, or in other words is not active or symptomatic, prior to the event in question. As the tortfeasor takes his or her victim as they find them, the tortfeasor is liable for all injuries even if the injuries are “unexpectedly severe owing to a pre-existing condition”, as a result of their actions: Athey at para. 34.
 In a crumbling skull situation, as in this case, the plaintiff has a pre-existing condition which is active, or likely to become active. The pre-existing condition “does not have to be manifest or disabling at the time of the tort to be within the ambit of the crumbling skull rule”: Barnes at para. 89, citing A. (T.W.N.) v. Clarke, 2003 BCCA 670 (CanLII), 2003 BCCA 670, 22 B.C.L.R. (4th) 1 at para. 62. In crumbling skull situations, the defendant is only liable for damages caused by the accident and responsible for returning the plaintiff to their original position. As Major J. stated in Athey: the defendant is liable for the additional damage but not the pre-existing damage: at para. 35. The defendant is therefore not liable for the effects of the pre-existing condition that the plaintiff would have experienced in any event: A. (T.W.N.) at para. 52. If there is a “measurable risk” that the pre-existing condition would have impacted the plaintiff in the future then, regardless of the defendant’s negligence, a court can take this into account in awarding damages: at para. 35.
 I conclude there was a real and significant chance that the plaintiff’s pre-existing injuries and the injury suffered after the Accident would have shortened the plaintiff’s career as a skating instructor, regardless of the injuries from the Accident. These injuries ultimately affect the plaintiff’s original position and must be taken into account in the assessment of damages. The risk that these injuries would have reduced the plaintiff’s chosen career will be taken into account based on its relative likelihood in determining the overall assessment of damages: McKelvie v. Ng, 2001 BCCA 341 (CanLII), 2001 BCCA 341, 90 B.C.L.R. (3rd) 62 at para. 17. Accordingly, non-pecuniary damages should be reduced by 10% to reflect such a risk.
 In assessing all of the relevant evidence, I conclude the injuries continue to adversely affect the plaintiff in a number of ways and award $75,000 for non-pecuniary damages. I will deduct 10% as a contingency to reflect the plaintiff’s pre-existing condition and the effect of the subsequent knee injury.