"As I mused, the fire burned"

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Legal Causation

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A snip from a case dealing with Workers’ Compensation matters. A main task is the assessment of causation, that is, did exposure to hazard A result in injury B? Sometimes that is straight-forward (a fall from height that results in broken bones), other times it is very challengine (small cell lung cancer after a past exposure to asbestos and a long history of smoking). The full decision is in the public domain at www.canlii.org. These are some of the hardest cases to hear and decide, as the injuries are almost always severe, and the consequences tragic.

The material is pretty dry, but I find such questions endlessly fascinating, as at their core is the question of truth.

In order to decide this appeal, the panel must determine whether or not the worker’s development of lung cancer was the result, even in part, of his occupational exposure to asbestos. Specifically, did the worker’s occupational exposure to asbestos or other workplace factors cause or contribute to the development of the lung cancer from which the worker died in 2010? As this is fundamentally a question of causation, we will review the legal tests to assess if there is a causal linkage between the worker’s employment and his lung cancer.

Causation decisions are made using the common law standard known as the but for test on a balance of probabilities. That is, can it be shown that but for the accident, there would have been no injury or adverse effects. That the first assessment of causation is done by considering the but for test was reaffirmed by the Supreme Court of Canada in Resurfice Corp. v. Hanke, [2007] 1 S.C.R. 333, 2007 SCC 7. In that case, the court wrote,

Further, the Court of Appeal erred in holding that the trial judge should have applied the ‘material contribution’ test to determine causation. The basic test remains the ‘but for’ test. […] The ‘material contribution’ test only applies in exceptional cases where factors outside of the plaintiff’s control make it impossible for the plaintiff to prove that the defendant’s negligence caused the plaintiff’s injury using the ‘but for’ test…

This is not a situation where the panel is considering negligence; however, the use of causation tests for compensation matters is a similar application. The Alberta Court of Appeal has been clear in stating that, barring policy that specifically establishes different causation principles from those in tort law, tort causation principles should be considered. In Shuchuk v. Alberta (Workers’ Compensation Board), 2007 ABCA 213, the appellate court wrote,

[40] I conclude that the Commission unreasonably interpreted the Policy by finding the MVA to be a substantially diminished cause of Shuchuk’s condition, such that the predominant effect of the intervening events precluded it from having any causal relationship. There is no line of analysis that could reasonably have led to such an interpretation given the Policy’s entitlement criteria and the underlying purpose of workers’ compensation scheme to provide generous coverage.

[41] I agree that the WCB, as part of its policy-making function, may develop a policy whereby causation principles applicable to the provincial workers’ compensation scheme differ from those principles applied by tort law… However, the WCB has not done so here as there is nothing in the Policy’s entitlement criteria that requires anything beyond a de minimus connection between the underlying accident and the personal injury.
[43] This conclusion is in keeping with the overall purpose to provide generous coverage under workers’ compensation schemes and gives effect to coverage for a psychological/psychiatric disability where the condition results from an emotional reaction to an accident, injury, physical disability, and/or the treatment process.
[46] … Absent clear legislative direction to the contrary, the workers’ compensation scheme should, at a minimum, provide compensation to those situations that would result in compensation under traditional tort law. Any interpretation of the legislative and policy regime that does not give effect to this principle is unreasonable.

In Shuchuk the court established that the intent of the compensation system is to provide generous coverage to injured workers on grounds similar to that of the tort system, and that there is no requirement established beyond a de minimus level. The legislation and policy assessed by the Court of Appeal has remained relatively static since that decision was written. So, without alternate causation principles outlined in WCB policy, in weighing this appeal we will consider the legal tests for causation described in the two cited court cases.

Considering these two court decisions in harmony guides the panel in assessing causation. First, we attempt to apply the but for test to determine if there can be a clear finding of causation made on that basis. If we cannot make a finding on that basis, and the underlying facts of the case permit satisfying the criteria of Resurfice Corp. v. Hanke, we can proceed to consider material contribution as the test for causation.

It is appropriate to comment at this point on the differing standards of causation applied by medical specialists and the legal tests which the panel is obligated to apply. While physicians assess the relationship between an injury and resultant symptoms using a scientific model, the task before the panel is to apply the correct legal test to the entire body of evidence. This includes evidence not considered by the physicians, such as that submitted at the hearing, but also the application of WCB policy and the Act to that evidence. This final step is also not considered by the medical reporting.

The panel must use the medical opinions on causation to help develop their legal assessment of causation. There is a difference between the medical and legal approaches to causation. The American Medical Association Guides to the Evaluation of Permanent Impairment, Sixth Edition, (AMA Guides) provides this comparison between the legal and medical tests for causation (page 25):

Legal terminology defines the association between an event and an outcome as ‘probable’ if it is more likely than not – if the probability of a cause and effect relationship is greater than 50%. There is a ‘possible’ causal relationship between a putative cause and an event when the likelihood of a causal relationship is equal to or less than 50%.

This is in contrast to standards in the scientific and medical literature, which require the likelihood that an association between a potential cause and an effect to be greater than 95% for the relationship to be considered ‘probable.’ Everything else is only possible.

In the definitions section of page 610, the AMA guides provide this definition for a cause:

In general, anything that produces an effect. In medicine, cause refers to an identifiable factor (eg, genetic abnormality, toxic or infectious exposure, trauma) that results in injury or illness. The cause or causes must be scientifically probable following causation analysis.

Compared to the legal causation test that this panel must apply, the medical test requires a higher degree of causal relationship. This distinction was recognized by the Supreme Court of Canada decision in Snell v. Farrell, 1990, 70 (S.C.C.), [1990] 2 S.C.R. 311:

Causation need not be determined by scientific precision.
Medical experts ordinarily determine causation in terms of certainties whereas a lesser standard is demanded by the law. It is the function of the trier of fact, not the medical witnesses, to make a legal determination of the question of causation.

This differing standard of scientific versus legal causation was emphasized within the workers’ compensation context by the Alberta Court of Queen’s Bench in Alberta (Workers’ Compensation Board) v. Alberta (Appeals Commission for Alberta Workers’ Compensation), 2010 ABQB 368. The court wrote at paragraph 87:

…there is a distinction between scientific and legal findings…At law, causation need not be determined with precision, but must meet the appropriate burden of proof…Policy 01-03, Part 1 provides that a worker need only prove their claim on a balance of probabilities, and if the evidence for and against a decision is equally balanced, the issue will be resolved in the worker’s favour. On the other hand, scientific analysis of causation seeks a far higher degree of certainty to establish causation.

The legal tests we are applying do not ask if the worker’s asbestos exposure played a primary or essential role in the development of lung cancer or if it was, based on scientific certainty, the main or probable cause of the cancer. Our question is if, on a balance of probabilities, but for the asbestos exposure there would have been no lung cancer or alternately, if the asbestos exposure materially contributed (that is, was more than a negligible contributor) to the development of the lung cancer at greater than a de minimus level.


Written by sameo416

March 9, 2012 at 9:51 pm

Posted in Uncategorized

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