Expert’s generic opinion doesn’t cut it: appellate court denies certification in cannabis class action

To certify a product liability or toxic substance class action, a plaintiff must provide some evidence of a workable methodology for proving that the defendant caused a loss on a class-wide basis. The methodology cannot be hypothetical; it must be grounded in the facts of the case. Recently, in Organigram Holdings Inc v Downton, the Nova Scotia Court of Appeal confirmed that a proposed methodology for establishing causation will not satisfy that requirement unless it connects the defendant’s alleged wrong to the specific harms asserted by class members. The Court found that the plaintiff’s expert evidence on causation was just a “generic opinion” which could not establish that connection and therefore denied certification.   

Background: Discovery of pesticides in cannabis leads to recall

The defendants sold medical cannabis. In late 2016, testing disclosed trace amounts of unauthorized pesticides in the defendants’ products. The defendants immediately notified Health Canada and initiated a voluntary recall.

Procedural history: Certification motion and appeal

The plaintiff consumed medical cannabis subject to the defendants’ recall. She commenced a class action asserting “consumer claims” alleging breaches of consumer protection laws and “adverse health consequences claims” seeking damages for adverse health effects.

A motion judge certified the class action. The defendants appealed. On appeal, they did not challenge certification of the consumer claims but argued that the health consequences claims should not have been certified. The Nova Scotia Court of Appeal agreed. It allowed the appeal in part and denied certification for the health consequences claims.

Plaintiff’s methodology disconnected from facts of the case

The defendants argued on appeal that the plaintiff had not provided a workable methodology to show that the recalled cannabis caused adverse health effects on a class-wide basis. Justice Bryson, writing for a unanimous court, agreed.

Justice Bryson cited several decisions holding that a plaintiff must provide a methodology for proving the defendant caused the alleged harm to the whole class to certify a class action alleging damage from harmful substances. He also referred to the Supreme Court’s holding in Pro-Sys Consultants Ltd v Microsoft Corporation that the methodology must “offer a realistic prospect of establishing loss on a class-wide basis” and “cannot be purely theoretical or hypothetical, but must be grounded in the facts of the particular case in question.”

The plaintiff’s expert witness had opined that it was possible to evaluate the risk to human health from consuming the pesticides found in the defendants’ products. Justice Bryson held that this was not sufficient to establish a workable methodology for two reasons:

  • First, virtually all the potential harms described by the plaintiff’s expert did not correspond to the symptoms mentioned by class members. The plaintiff and another class member provided evidence that they suffered from nausea, vomiting, dizziness, breathing difficulties and headaches after consuming the defendants’ products. The expert opined that pesticides found in the defendants’ products could cause some different adverse health effects, but he did not say that the pesticides could cause the symptoms class members complained of.  
  • Second, the methodology proposed by the plaintiff’s expert failed to address the specific alleged class‑wide wrong. He gave a general opinion that it was possible to identify harms caused by exposure to pesticides. However, he never provided evidence that it was possible to show that class members suffered adverse health effects from the minimum exposure experienced by each class member.

Additionally, the plaintiff was unable to say that exposure to the pesticides could be linked to any specific illness. Justice Bryson held that the wide array of common, generic and transient symptoms described by the plaintiff were not capable of a common cause determination.

Justice Bryson therefore found that the expert’s “generic opinion” was not evidence of a workable methodology and denied certification for the health consequences claims.


Organigram v Downtown confirms that the workable methodology requirement is not a rubber stamp. In particular, it demonstrates that courts will not allow a class action to proceed on the basis of a theoretical expert methodology that fails to grapple with the actual facts of the case.