Evidence is required to establish “some basis in fact” for the procedural preconditions to certification. This requires certification judges tread the fine line between screening out inappropriate class proceedings and impermissibly weighing of the merits of the claim based on evidence at the certification stage. The Alberta Court of Appeal’s recent decision in Warner v. Smith & Nephew Inc. (Justice Slatter dissenting) illustrates the continuing evolution of the evidentiary threshold required for certification.

Competing Expert Reports on Causation

The plaintiff in Warner alleged a hip resurfacing system caused toxic levels of metal ions in the blood and applied for certification of a class action against the manufacturer. Each party filed an expert report opining on, among other things, causation of metal ions in the blood. The plaintiff’s proposed expert concluded that there was a “great deal of uncertainty as to what the presence of serum metal ions actually means for the patient”.

The certification judge denied certification, finding that class proceedings were not a preferable method for resolving the common issue because there was very little prospect of the plaintiff succeeding.

Court of Appeal Disagrees on Weight of Expert Evidence

On appeal the majority reversed the chambers decision and certified the class action. In doing so, the majority held that the certification judge improperly considered whether there was “some basis in fact” for the claim itself, rather than analyzing whether there was “some basis in fact” that a class action was a preferable procedure.

In dissent, Justice Slatter reasoned that some minimal evidentiary basis for the claim was required in order to show a class proceeding was a preferable procedure. Based on the expert evidence Justice Slatter found it “uncontradicted” that no one knew the long term effects of metal ions in the blood. In the face of an unresolved “scientific mystery”, Justice Slatter was of the view that the plaintiff failed to establish an expert methodology that might demonstrate causation.

The majority disagreed, concluding that “[t]he existence of a scientific controversy, particularly at the certification stage, is not determinative of the merits of the claim”. Further, the majority questioned whether the “expert methodology” requirement described in Pro-Sys Consultants Ltd. v. Microsoft Corporation and Sun-Rype Products Ltd. v. Archer Daniels Midland Company applied to establishing the elements of a negligence claim.

Continuing Uncertainty in Weight of Evidence

Warner underscores the continuing uncertainty regarding the weight a certification court will give to evidence in assessing whether the procedural requirements for certification have been met. This issue has arisen frequently when assessing the evidentiary threshold for the requirement of a class-wide methodology to prove causation. For example, see our posts on Miller v. Merck Frosst Canada Ltd. and Charlton v. Abbott Laboratories, Ltd. Going forward courts will continue to tread the fine line between fulfilling their gate-keeping function and impermissibly weighing the merits at the certification stage.