This post is the third in a row about expert evidence.

The first post discussed Moore v Getahun, 2015 ONCA 55, and its conclusion that consultations between counsel and experts about draft reports are appropriate and presumptively privileged.

Next up was Westerhof v Gee Estate, 2015 ONCA 206, which held that certain treating practitioners can provide opinion evidence about a party’s medical condition without having to comply with the formalities of a traditional expert report under the Ontario Rules.

Now, we have a landmark judgment about expert evidence from the Supreme Court of Canada on another aspect of expert evidence: Admissibility in the face of challenges to a proposed expert’s independence and impartiality.

In White Burgess Langille Inman v Abbott and Haliburton Co, 2015 SCC 23 [“WBLI”], an appeal from Nova Scotia, Justice Cromwell for a unanimous Court confirmed that there is a “threshold admissibility requirement” related to independence and impartiality: The trial or motion judge, as gatekeeper, must be satisfied that the expert will abide by her duty to the court to give independent and impartial evidence that is free of bias (paras 1-2, 10, 34, 45-46).

This duty is not sufficiently safeguarded if all concerns about independence and impartiality are left to be weighed at the end of the proceeding; the gatekeeper must flex some muscle at the beginning of the proceeding to protect it (see e.g. para 45). How much muscle, exactly, will depend on the circumstances.

Safeguarding independence and impartiality

The three cases comprising the ‘trilogy’ of blog posts—MooreWesterhof, and now WBLI—address different angles of the law on expert evidence. But they all share the same objective, at least in part: Ensuring experts uphold their duty to the court to give independent and impartial evidence. This duty has been enshrined in the civil procedure rules of many provinces, including in Nova Scotia Civil Procedure Rule 55.04(1), but also exists at common law (paras 29-31).

The raison d’être for this duty is, of course, to prevent miscarriages of justice (para 12).

Justice Cromwell in WBLI defined impartiality and independence, and then set out the “acid test” for admissibility (para 32):

Underlying the various formulations of the duty are three related concepts: impartiality, independence and absence of bias. The expert’s opinion must be impartial in the sense that it reflects an objective assessment of the questions at hand. It must be independent in the sense that it is the product of the expert’s independent judgment, uninfluenced by who has retained him or her or the outcome of the litigation.  It must be unbiased in the sense that it does not unfairly favour one party’s position over another. The acid test is whether the expert’s opinion would not change regardless of which party retained him or her [emphasis added].

The impartiality problem arose in WBLI on a motion to strike a proposed expert’s affidavit (paras 4-6). This was part of a broader summary judgment motion in a professional negligence action, in which a group of shareholders were suing their company’s former auditors. The alleged negligence of the defendant auditors was discovered by a branch of Grant Thornton in Kentville, Nova Scotia; the shareholders’ proposed expert was a forensic accounting partner from Grant Thornton in Halifax. The defendants said she could not be impartial because she could have a potential personal financial stake in the outcome of the case, as a partner with the firm. The motion judge agreed and struck the affidavit; a majority of the Nova Scotia Court of Appeal overturned that decision.

Ending the debate of admissibility vs weight

Can the trial judge just let the potentially biased expert through the gate at the outset so her evidence can be heard, leaving the trier of fact to decide what to do with it later when weighing the whole of the evidence? No.

According to Justice Cromwell, issues of independence and impartiality have to be considered at both junctures – when considering admissibility of the evidence in the first place, and when considering the ultimate weight to give to the evidence (assuming it was not previously excluded) (para 45).

Justice Cromwell quoted Justice Binnie from the earlier case of R v J-LJ, [2000] 2 SCR 600: “The admissibility of the expert evidence should be scrutinized at the time it is proffered, and not allowed too easy an entry on the basis that all of the frailties could go at the end of the day to weight rather than admissibility” (WBLI at para 45).

By reaching this conclusion, the Court resolved an ongoing debate in the case law.

Clarifying the test

The threshold admissibility requirement had to be shoehorned into the overall framework for admitting expert evidence – which, as we know, is already a tightly controlled exception to the general exclusion of opinion evidence. This is where the Supreme Court meshed its seminal decision in R v Mohan, [1994] 2 SCR 9 with the Ontario Court of Appeal’s 2009 decision in R v Abbey, 2009 ONCA 624, which it finally adopted after refusing leave to appeal in 2010 (and mentioning the case in a few other decisions since then).

At several points in his reasons, Justice Cromwell reviewed how the analytical pieces fit together (see especially paras 16-25 and 46-53). What follows is an attempt to compile the pieces into one succinct checklist, with the ‘new’ parts of the test in italics:

I.                Admissibility of expert evidence: Trial judge as gatekeeper

(1)  Stage 1 – Threshold admissibility

  • Application of Mohan factors – Expert evidence must be:
    • Relevant
    • Necessary to assist the trier of fact
    • Otherwise admissible (no other exclusionary rule applies)
    • {Based on reliable underlying science, if opinion “based on novel or contested science or science used for a novel purpose}
    • Given by a properly qualified expert – This is where the *initial* assessment takes place of the expert’s ability to comply with the duty to the court to remain independent and impartial:
      • Generally, the expert’s oath/affirmation will suffice to show compliance with the duty to the court (although note that this does not rise to the level of a presumption)
      • If there is a challenge to the expert, “the burden is on the party opposing the admission of the evidence to show that there is a realistic concern that the expert’s evidence should not be received because the expert is unable and/or unwilling to comply with that duty”
      • Then the party proffering the evidence must prove on a balance of probabilities that the expert is independent and impartial, and otherwise properly qualified
      • If the trial judge concludes the expert is “unable or unwilling” to comply with the duty, the evidence must be excluded at this stage – but this will “likely be quite rare”

(2)  Stage 2 – Cost-benefit analysis

  • Balancing of risks and benefits of admission of expert evidence
    • This balancing can also incorporate “concerns about the expert’s independence and impartiality

II.                Weight of expert evidence: Trier of fact (judge or jury)

  • The trier of fact can still factor in a potential lack of independence and/or impartiality when weighing the evidence

Note that a motion judge will likely only apply the first step (threshold admissibility), because the cost-benefit analysis at the second step “inevitably involves assigning weight—or at least potential weight—to the evidence” (para 55).

Applying the test

Justice Cromwell set a high bar, stating that “exclusion at the threshold stage of the analysis should occur only in very clear cases in which the proposed expert is unable or unwilling to provide the court with fair, objective and non-partisan evidence” (para 49; emphasis added).

This is not a reasonable apprehension of bias-type test; as Justice Cromwell reiterated, the “‘appearance’ of impartiality” to a reasonable observer “plays no part in the test for admissibility” (paras 50, 57).

Factors that could, however, require exclusion include (see para 49):

  • “a direct financial interest in the outcome of the litigation”
  • “a very close familial relationship with one of the parties”
  • the probability of expert incurring professional liability if opinion not accepted

The fact that an expert has been “retained, instructed and paid” by the party calling her does not automatically meet the threshold (para 32). Justice Cromwell also noted that a “mere employment relationship with the party calling the evidence will be insufficient” to have it excluded (para 49).

On the facts of WBLI, the Supreme Court agreed with the majority of the Court of Appeal that the evidence of the Grant Thornton expert was admissible; “her evidence was clear that she understood her role as an expert and her duty to the court” and there was no competing evidence of a conflict of interest that would call her compliance into question.


The Supreme Court’s decision in WBLI is the cherry on top of a recent batch of cases on expert evidence. Not only does it entrench the expert’s fundamental duty to the court to remain independent and impartial, but it clarifies the analytical steps the trial judge must take when deciding the admissibility of expert evidence. Both experts and gatekeepers will know their roles a bit better after this decision.