Developments in General Causation Methodologies for Class Certification

June 01, 2023

Written By Ethan Schiff and Julien Sicco

In product liability class actions, general causation (i.e., a product's propensity to cause alleged injuries) is often a threshold issue to establish liability (if general causation cannot be established, no class member's claim is viable). This concept is distinct from and precedes specific causation (i.e., whether the product caused a particular injury). Because specific causation often cannot be determined in common, to certify a class action, plaintiffs may need evidence of a methodology to prove general causation.

Over the previous year, courts delivered two cases relevant to (1) the circumstances in which a plaintiff will need to give evidence of a methodology for determining general causation, and (2) the requisite contents of such a methodology.

When is a Methodology to Establish General Causation Required for Certification?

In Hyundai Auto Canada Corp v. Engen [Engen], the Alberta Court of Appeal upheld certification of a class action alleging that sunroofs in six vehicle models were susceptible to spontaneous shattering. On appeal, the defendants argued that the plaintiff failed to provide evidence of a methodology to establish that a particular defect can cause the alleged spontaneous sunroof shattering. The Alberta Court of Appeal rejected this argument, in part, because the court held that no such methodology was required.

Engen's approach may be contrasted with that of the British Columbia Court of Appeal's 2018 decision in N&C Transportation v. Navistar International Corporation [Navistar], where the court stressed that, at certification, there must be "some methodology capable of proving that a common defect caused a common impact". The court there concluded that the plaintiffs' evidence was sufficient to determine if the specific exhaust control system at issue could cause the alleged various performance and operational issues, including, among other things, engine overheating, fuel pump leakage, recalculating valve damage, fan hub damage and soot buildup in the particulate matter traps.

Engen is consistent with Navistar in the context of the distinct characteristics of the underlying alleged defect and consequential harms. Engen engaged a relatively straightforward causal connection between an alleged defect and a single negative outcome (spontaneous sunroof shattering). By contrast, in Navistar, the causal connection between the exhaust control system and the multiple alleged operational and performance problems was not as obvious. Engen may indicate that, when a single defect in a product component is alleged to cause a single negative outcome to that component resulting in injury, no general causation methodology is required.

Circumstances engaging more variable defects and alleged failure modes may, however, trigger an obligation by plaintiffs to demonstrate the availability of a credible or plausible methodology to determine general causation.

What Degree of Specificity is Required for a Methodology to Determine General Causation?

Courts often consider methodologies for determining general causation in cases alleging defects in pharmaceuticals. In Price v. Lundbeck A/S [Price] the Ontario Superior Court of Justice dismissed a motion to certify a class action about alleged birth defects resulting from the use of Celexa because the proposed methodology was not sufficiently tailored to the alleged negative outcomes.

The plaintiffs in Price alleged that Celexa is a teratogen (i.e., an agent that can, under reasonable circumstances of exposure, disturb the development of an embryo or fetus and cause congenital malformations). The plaintiffs further alleged that based on Celexa's teratogenicity, class members may suffer from hundreds of variable congenital malformations for which there is "no common etiology". In order to support these allegations, the plaintiffs in Price proposed a general causation methodology that would determine if Celexa is a teratogen, but would not determine if Celexa consumption can cause the alleged injuries (i.e., the specific congenital malformations).

The court in Price concluded that the plaintiffs' proposed methodology was deficient because it would not establish if consumption of Celexa can cause any specific congenital malformations. In the Court's description, "'[t]eratogenicity' is not the harm suffered, but instead a term that relates to the possibility of hundreds of congenital malformations, only some of which (if any) might have been reasonably foreseeable." On this basis, the court declined to certify the proposed common issue.

The court in Price warned against certifying cases based on "superficial commonality" such as the generalization of teratogenicity, as distinct from the specific harms alleged.

Looking Forward

Taken together, Engen and Price suggest that, for certification, proposed product liability class actions will require evidence of a methodology to prove general causation of the specific injuries alleged if the connection between the defendants' conduct and the class' resulting damage is unclear and/or if multiple negative outcomes are alleged.

As Price demonstrates, courts are likely to scrutinize the proposed methodology to ensure that it establishes commonality that is material to the alleged harms. A methodology that only demonstrates commonality in overly broad terms will not satisfy the certification requirements.

Litigants and their counsel facing product liability class actions should closely scrutinize the allegations of harm and consider the limitations of any evidence that the alleged harms flow from the underlying product defect. If common general causation can only be demonstrated on an illusory basis, certification may not be appropriate. 

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