What’s the test? Admissibility of Expert Opinion Evidence in Certification Applications
The Saskatchewan Court of Queen’s Bench in Stout v. Bayer Inc., 2017 SKQB 329 (“Stout”) confirmed that the same standard for the admissibility of expert evidence applies in class action certification applications as in other proceedings. Evidence must satisfy the test for admissibility before it will be considered in the context of certification. As such, the lesser standard of proof associated with the statutory certification requirements does not reduce the threshold of admissibility of expert opinion evidence in certification applications.
Facts in Stout
Stout is a proposed class action concerning the Essure Permanent Birth Control System (“Essure”), a permanent form of female birth control. The plaintiffs in Stout allege that the defendants are liable under various causes of action for, among other things, the development, testing, manufacture, promotion, distribution and sale of Essure.
In support of an application to certify the action as a class proceeding, one of the representative plaintiffs filed affidavits of two purported expert witnesses. Before the certification application was heard, the defendants sought an order to strike certain paragraphs of the first witness’ affidavit and an order striking the entire affidavit of the second witness.
The defendants challenged the evidence on the basis that it did not meet the threshold requirements for admissibility of expert opinion evidence. The plaintiff contended that the lesser standard of proof required to establish the requirements for certification – “some basis in fact”-applied to expert evidence. The issue before the court was whether the affidavits, or portions thereof, were properly admissible in the application to certify the proposed class action.
Admissibility of evidence & standard of proof for certification
For admissibility of expert opinion evidence, the Supreme Court of Canada established a two-part test in R v Mohan,  2 SCR 9 (“Mohan”), and restated in White Burgess Langille Inman v Abbott and Haliburton Co, 2015 SCC 23 (“White Burgess”). Expert evidence is admissible when:
(i) the four threshold requirements of admissibility are satisfied and
(ii) the benefits of admitting the evidence outweigh its potential risks.
The four threshold criteria for the admission of expert evidence are (i) relevance, (ii) necessity, (iii) absence of any exclusionary rule and (iv) a properly qualified expert. With respect to the qualification requirement, Justice R.W. Elson in Stout noted that impartiality, independence and absence of bias should be considered.
Relative to the general standard of admissibility, the standard of proof for certification is low. A representative plaintiff only needs to present sufficient evidence to establish “some basis in fact” for each of the certification requirements set out in the section 6(1) of The Class Actions Act.
The two-part test applies in certification proceedings
The court in Stout held that the two-part Mohan test applies equally to evidence adduced in certification applications. Justice R.W. Elson stated, “[w]hile the ‘some basis in fact’ standard of proof is clearly less than balance of probabilities standard, it does not diminish the application of the admissibility requirements, including those applicable to expert opinion evidence.”
Analysis of the affidavits in Stout
The proposed affidavits were sworn by a nutritional epidemiologist with a doctorate in physical activity and nutritional epidemiology and an attorney from the United States with an undergraduate degree in astronomy and physics as well as a law degree.
The first witness deposed that she was asked to provide an expert opinion concerning “pharmacoepidemiology, adverse event reporting systems, and methods for assessing general causation for medical devices and adverse events.” However, in cross-examination, she acknowledged that her training did not extend to the topic on which she opined. Rather, her opinion was based on the review of literature published by experts in the field. As such, the court found that the witness was not qualified to provide expert evidence with respect to the use of Essure, including its efficacy, labelling and potential for harm. Her expertise in one field was not transferable to another by simply acquiring information without any specific training or experience in the subject matter.
The second witness deposed that he was qualified as an expert in the Federal Court of Canada to give evidence on adverse event reporting generally and adverse event reporting systems. However, in cross-examination, he admitted that in forming his opinion, he only considered evidence obtained from the plaintiff, deliberately discounting information that may support an alternative conclusion. Based on this factor alone, the court found that, in addition to the witness’ lack of training in health-related matters, he did not qualify as an expert because he lacked independence in his opinion.
Given that Justice R.W. Elson found that neither of the expert witnesses was properly qualified to give an opinion on the commonality of any of the proposed issues, the court did not proceed to the second part of the test. The court granted the defendants’ application, finding that the contents of the affidavits did not meet the threshold requirement for admissibility of expert evidence.
 Stout at para 5.
 Ibid at para 4.
 Ibid at para 11.
 Ibid at para 29.
 Ibid at para 30.
 White Burgess at paras 19 – 24.
 Stout at para 43.
 Stout at para 49.
 Ibid at para 11.
 Ibid at para 14.
 Ibid at para 11.
 Ibid at para 19.
 Ibid at para 13.
 Ibid at para 16.
 Ibid at para 47.
 Ibid at para 51.
 Ibid at para 23.
 Ibid at para 55.