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Expert Opinions: Beware a Biased Expert

By Celina Stoan

In Denman v. Radovanovic, 2022 ONSC 4401, following a July 18, 2022, mid-trial voir dire, Justice Ferguson ordered the defence’s expert Dr. Redekop excluded from testifying on the grounds of bias. The 35th paragraph of Her Honour’s decision reads “This is the first time I have done this with an expert since being appointed in 2004”.

The Test to Admit Expert Evidence

In her reasons, Justice Ferguson reiterates the gatekeeping role of the trial judge and explains the test for admissibility of expert evidence. While the initial test was described in R. v. Mohan as being a four prong analysis, the test is now divided into two steps.

At the first step (or threshold step), the court applies the Mohan criteria: relevance, necessity in assisting the trier of fact, the absence of any exclusionary rule and a properly qualified expert. At the second discretionary gatekeeping step, the court balances the potential risks and benefits of admitting the evidence.

Justice Ferguson also cited Morris v. Prince, where the trial judge said “I must avoid the temptation to take the path of least resistance and rule the evidence admissible subject only to the weight to be afforded to such evidence.” As such, it appears that where there is a question of expert bias, there is a tendency by judges to allow the expert evidence to be admitted, and to allow the trier of fact to determine how much weight to give to it.

In White Burgess, the Supreme Court of Canada reviewed whether/when evidence of bias goes to admissibility versus weight as such: if experts cannot fulfill their duty to the court to give fair, objective and non-partisan opinion evidence, their evidence should not be admitted. If however they can meet this threshold, concerns about their independence or impartiality should be considered as part of the overall weighing of the costs and benefits of admitting the evidence.

In Wise v. Abbott Laboratories, Limited, the court cited a list of 14 factors that may be considered when ascertaining bias and impartiality. In the subject voir dire eight of the 14 considerations[1] were at play:

  1. a history of retainer exclusively (or nearly so) by the prosecution or the defence,
  2. long association with one lawyer or party,
  3. personal involvement or association with a party,
  4. lack of a report, a grossly incomplete report, modification or withdrawal of a report without reasonable explanation, a report replete with advocacy and argument;
  5. performance in other cases indicating lack of objectivity or impartiality,
  6. unexplained differing opinions on near identical subject matter in various court appearances or reports;
  7. inaccessibility prior to trial to the opposing party, follow through on instructions designed to achieve a desired result, shoddy experimental work, persistent failure to recognize other explanations or a range of opinion, lack of disclosure respecting the basis for the opinion or procedures undertaken, operating beyond the filed of stated expertise, unstated assumptions, work or searches not performed reasonably related to the issue at hand, unsubstantiated opinions, improperly unqualified statements, unclear or no demarcation between fact and opinion, unauthorized breach of the spirit of a witness exclusion order; and
  8. expressed conclusions or opinions which do not remotely relate to the available factual foundation or prevailing special knowledge.

Impartiality is a question of fact. Exclusion at the threshold stage should only occur in very clear cases in which the proposed expert is unable or unwilling to provide the court with fair, objective and non-partisan evidence.

The Voir Dire

This case was a medical malpractice action. Dr. Redekop described himself as a “professional friend” to the defendant physicians. One of the defendant physicians, Dr. Ter Brugge, described him as a friend and Dr. Redekop advised that he took this as a compliment as he sees himself as a peer/colleague. Dr. Redekop and Dr. Ter Brugge also co-authored some articles/papers. Dr. Redekop did not expressly include a comment in his reports that he had a prior relationship (friendship, professional or otherwise) with Dr. Ter Brugge.

Dr. Redekop advised that he took the evidence of one of the plaintiffs and the discovery report of another into account when writing his reports, however he did not reference it in his report. While Dr. Redekop has provided opinions to both plaintiff’s and defendants, in medical malpractice cases he provides opinions for the defendants only – this received judicial scrutiny. Dr. Redekop agreed that he had never testified that a physician failed to meet the standard of care.

Justice Ferguson also noted several instances during Dr. Redekop’s cross-examination where he opined on percentages of risk which were not accurate and were favourable to the defence. Dr. Redekop also made assumptions that there was greater discussion between the doctors and the plaintiffs than what was charted based on defence evidence of general/standard practice. He also agreed that he assumed that the content of these uncharted discussions met the standard of care.

Justice Ferguson candidly admitted that she tried to defer admissibility of Dr. Redekop’s evidence to closing submissions but was persuaded otherwise by the above-noted caselaw which states that “the trial judge must avoid the temptation to take the path of least resistance and rule the evidence admissible subject only to weight”.

In excluding Dr. Redekop’s evidence, Justice Ferguson agreed with a number of submissions of plaintiff’s counsel, including:

  • that the expression of an opinion as to the credibility of a witness is a breach of the expert’s duty to be independent, and by assuming that the defendant’s evidence was credible and reliable, Dr. Redekop had breached that duty;
  • Dr. Redekop provided an opinion with respect to his friend, teacher, co-collaborator Dr. Ter Brugge – without disclosing this in the face of the acknowledgement of a duty of transparency;
  • The content of Dr. Redekop’s report is profoundly inadequate;
  • Dr. Redekop used a “pick and choose” opinion to come to a conclusion that supports his colleague physician defendants;
  • Dr. Redekop was not impartial;
  • Dr. Redekop violated eight of the considerations.


Medical experts should be thoroughly researched. It is important that, if possible, counsel select an expert who testifies both for plaintiffs and defendants, has no link to any of the counsel or parties, and authors accurate reports which are persuasive, but not advocacy.

The duty of the expert is to assist the court. The expert has an obligation to offer evidence which is impartial and non-partisan. This obligation supersedes any retainer obligations.

[1] An interesting consideration which was not at play was “whether a significant percentage of the expert’s income is derived from court appearances”.