In British Columbia (Workers’ Compensation Appeal Tribunal) v. Fraser Health Authority,  SCC 25 (hereinafter “WCAT 2016”) the Supreme Court of Canada was asked to look at causation in the context of a cluster of seven British Columbia medical technicians who developed breast cancer while working at the same hospital laboratory. Three of the seven workers applied for worker compensation benefits.
A Compensation review officer denied the claim for benefits. Medical experts who reviewed the case had concluded there was insufficient evidence to sufficiently link breast cancer to laboratory work. The workers appealed to the Workers’ Compensation Appeal Tribunal and it found that the breast cancers were occupationally caused diseases in this case. The employer then applied for judicial review and the Workers’ Compensation Appeal Tribunal decision was overturned. An appeal to the British Columbia Court of Appeal by the 3 workers was not successful. The workers appealed to the Supreme Court of Canada (the “Court”).
... the distinction between causation under workers’ compensation law and under tort law
In a split decision of the Court, the majority highlighted the distinction between causation under workers’ compensation law and causation under tort law. Under workers’ compensation law where evidence is evenly weighted on causation, causation is resolved in the workers’ favour. Under tort law, evenly weighted causation evidence results in failure of a worker or plaintiff’s claim. However, the Court also noted that the ‘causation’ distinction was not determinative in this case.
The majority stated at paragraph 33 that the Courts below had fundamentally misapprehended how causation, “irrespective of the standard of proof – may be inferred from the evidence.” Going back to first principles, the majority restated at paragraph 38 that:
“The presence or absence of opinion evidence positing (or refuting) a causal link is not, therefore, determinative of causation... It is open to the trier of fact to consider, as this Tribunal considered, other evidence in determining whether it supported an inference that the workers’ breast cancers were caused by their employment...”
The majority of the Court then went one step further to tacitly endorse what might be considered an expansion of defined occupational disease in the context of causation, work-related illness, and possibly tort law:
“Howsoever “positive evidence” was intended to be understood in those [cited] decisions, it should not obscure the fact that causation can be inferred – even in the face of inconclusive or contrary expert evidence – from other evidence, including merely circumstantial evidence. This does not mean that evidence of relevant historical exposure followed by a statistically significant cluster of cases will, on its own, always suffice to support a finding that a worker’s breast cancer was caused by an occupational disease. It does mean, however, that it may suffice.”
WCAT 2016 will likely become one of the more frequently cited cases on causation generally and in the context of occupational disease. It seemingly opens the door a little wider – and to a broader definition of occupational disease based on statistical inference and medical case clusters. Medical clusters were once the bailiwick of epidemiologists – who now may become the Court’s experts of tomorrow in many potential class action lawsuits. And, “Getting Back to the Future”, Michael J Fox might just have a case...