The expert witness’s duty of impartiality in Canada

In the 2015 case of White Burgess Langille Inman v Abbott and Haliburton Co., ¹ the unanimous Supreme Court of Canada held that expert witnesses have a special common law duty to provide ‘fair, objective and non-partisan assistance’ to the court and that trial judges should properly exclude such testimony if the proposed expert lacks sufficient independence and impartiality. ² In so holding, the court continued the trend in Canadian law of tightening admissibility requirements and aligned its approach with recent case law from England. In our view, this Anglo-Canadian position contrasts favourably with the approach generally followed in Australia and the United States, where questions of an expert’s lack of impartiality are directed solely to weight, rather than to admissibility.

The appeal arose out of a professional negligence action. The respondents, shareholders of a hardware company, sued the appellants, an accounting firm they had previously hired to conduct an audit of their business. The suit was commenced after the respondents learned, from a different audit company, that the appellants had made various mistakes that were alleged to have caused financial loss to the respondents. As part of proving their claim at trial, the respondents sought to call a forensic accountant (who worked at the accounting firm that had discovered the mistakes) as an expert witness who would offer an opinion that the appellant firm failed to comply with its professional obligations. The appellants challenged the expert on the basis that she was not impartial. According to the appellants, the expert necessarily had an interest in the outcome of the litigation on the basis that if her opinion was rejected by the court she might personally expose herself to a claim for professional negligence by the respondents. In the course of dismissing the appeal, the court articulated a new framework for disqualifying expert evidence where it lacks sufficient independence and impartiality.

The court began its analysis by affirming that expert witnesses have a special duty, existing at common law, to provide the court with ‘independent assistance…by way of objective and unbiased opinion’. ³ This duty is underpinned by the three concepts of impartiality, independence and absence of bias. First, the opinion must be ‘impartial in the sense that it reflects an objective assessment of the questions at hand’. ⁴ Secondly, the opinion must be the ‘product of the expert’s independent judgment, uninfluenced by who has retained him or her or the outcome of the litigation’. ⁵ Finally, the opinion must be ‘unbiased in the sense that it does not unfairly favour one party’s position over another’. ⁶ The ‘acid test’ for this latter requirement is whether the opinion ‘would not change regardless of which party retained [the expert]’. ⁷ Having set out the nature of the duty, the court observed that a threshold admissibility requirement applied in relation to the duty ‘in addition to…the weight to be given to the evidence if admitted’. ⁸

This finding is broadly consistent with the position in England. For example, in Armchair Passenger Transport Limited v Helical Bar Plc, ⁹ the High Court reviewed a number of relevant cases and drew up a list of principles in relation to the independence and impartiality of expert witnesses. According to the High Court, where an expert has an interest in the outcome of the case, the judge must decide ‘whether [the] expert should be permitted to give evidence’. ¹⁰ The decision on admissibility is a question of ‘fact and degree’ and depends, in part, on whether the proposed expert ‘is aware of their primary duty to the Court…and willing and able, despite the interest or connection with the litigation or a party thereto, to carry out that duty’. ¹¹ In the event the expert’s evidence is admitted, the court will consider how ‘an interest which is not sufficient to preclude him from giving evidence’ will affect the weight to be accorded to the expert’s opinion. ¹² The Canadian position departs, however, from the positions in both Australia and the United States. In those jurisdictions, arguments about an expert’s lack of impartiality are matters going solely to weight; alleged bias does not, of itself, constitute a reason for excluding the expert’s evidence. ¹³ In FTG Custodians Pty Ltd v Fagenblat, ¹⁴ for instance, the Supreme Court of Victoria, Court of Appeal rejected the argument that an interest in the case could implicate the competency of an expert witness to testify. The court reviewed the development of strictly applied common law competency rules, which were abolished by Parliament in the nineteenth century. ¹⁵ According to the court, for ‘at least 100 years if not far longer’, the remedy for the criticism of an expert witness ‘has not been seen in denying the right of such witnesses to give evidence; rather it has been seen in devising court rules and protocols which will ensure that experts will try to be independent and that courts will not unnecessarily suffer the opinions of experts who may be thought to be in one camp or the other.’ ¹⁶ The court expressly declined to lay down a new common law rule that would exclude expert witness evidence unless it passed a threshold assessment of its impartiality. ¹⁷

Having set out the nature of an expert’s requisite independence and impartiality, the Supreme Court of Canada moved on to explain how this duty integrated into the current regime for admitting expert opinion evidence more generally. In Canada, such evidence must pass what is now known as the two-stage Mohan framework. ¹⁸ Under the first stage, four threshold questions must be satisfied: the opinion must be (i) relevant; (ii) necessary in the sense that the trier of fact requires assistance in drawing the inference offered by the expert; (iii) there must be no other exclusionary rule barring admission; and (iv) the expert must be properly qualified. ¹⁹ The second stage calls for a cost-benefit analysis, wherein the trial judge must be satisfied that the probative value of the opinion outweighs its potential for prejudice. ²⁰ The court in White Burgess explained that the expert’s duty of impartiality and independence should be considered under both stages of the Mohan framework. In the first stage, it is relevant to the expert’s proper qualifications. ²¹ Put simply, a properly qualified expert must be both aware of and willing to carry out his or her duty to the court to be impartial and independent. ²² The expert’s attestation ‘recognizing and accepting the duty will generally be sufficient’. ²³ However, the party opposite may challenge the expert by showing a ‘realistic concern’ that he or she is unable or unwilling to comply with this duty. ²⁴ In this event, the proponent of the evidence must prove on the balance of probabilities that the expert understands and intends to carry out his or her duty to the court; failure to do so renders the evidence inadmissible. ²⁵ The court emphasised that the threshold here is ‘not particularly onerous’ and that it will ‘likely be quite rare’ that an expert fails to meet it. ²⁶ In assessing this, courts should consider the nature and extent of a party’s interest in the litigation, not merely the fact that they have an interest or a connection. Having an employment relationship with one party will not itself disqualify an expert; but ‘having a direct financial interest in the outcome of the litigation will be of more concern’. ²⁷ Of particular note is the court’s holding that the question of impartiality at this stage is not related to perceptions of bias in the eyes of a reasonable observer. ²⁸ Ultimately, the analysis is a contextual one, and disqualification 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’. ²⁹

If the first stage of Mohan is passed, the proponent of the evidence must then satisfy the trial judge that the probative value of the proposed expert’s evidence outweighs its potential for prejudice. Here the judge acts in a gatekeeping role, holding a ‘residual discretion to exclude evidence based on a cost-benefit analysis’. ³⁰ In relation to the present duty, the trial judge is to take into account ‘[l]ess fundamental concerns about an expert’s independence and impartiality’. ³¹ While the court was not as explicit in setting out factors to consider under this stage of Mohan as one may have liked, it is clear that the court sees value in preserving discretion for the trial judge to make an assessment on the ultimate question of admissibility. In our view, the probative value of expert evidence should be determined largely by the reliability of the opinion, which will in turn depend upon a careful reassessment of the nature and degree of the expert’s interest in and connection to the parties and the litigation. ³² There might also be an opportunity for the trial judge to take into account broader interests such as perceptions of bias, particularly in relation to the potential harm that might flow from the admission of the evidence.

Having clarified the above principles, the court turned to apply them to the dispute before it. As mentioned above, the appellant’s primary submission was that the expert was not impartial as she risked exposing herself to personal liability in the event that her planned testimony about the appellant’s professional negligence was ultimately rejected at trial. The court dismissed this argument out of hand, finding that it was nothing more than a ‘speculative possibility’. ³³ The court further observed that the expert had testified that she was in fact aware of guidelines in the accounting industry for acting as an expert witness and that she had expressly acknowledged that she owed an ultimate duty to the court. ³⁴ Finally, the court determined that the fact that the expert worked for the accounting firm that had discovered (and initially disclosed) the appellant’s alleged mistakes, and had incorporated parts of her firm’s mathematical analysis into the opinion she intended to deliver, was not suggestive of bias and did not compromise her independence. ³⁵ Absent a realistic concern of bias, her acceptance of the duty of impartiality and independence was held to stand, and the appeal was dismissed accordingly.

White Burgess is a welcome decision in that it responds to the call for Canadian courts to ‘articulate a clear test to determine when an expert’s impartiality or independence has been compromised to such a degree as to attract sanction’. ³⁶ According to David Paciocco, ‘there is increasing recognition in Canada that experts owe…a fiduciary duty to the courts and tribunals they seek to enlighten’ (Paciocco, 2009: 570). While the court in White Burgess referred to the ‘special duty’ that expert witnesses owe to the court at common law, as opposed to a fiduciary relationship, the decision clearly recognises the important role played by experts in the modern trial process and the vigilance that must be maintained to safeguard the reliability of the evidence. As noted above, courts in Australia and the United States generally treat concerns about an expert witness’s bias as going solely to weight. While there can be no dispute that such concerns ought to inform weight, in our view the Supreme Court of Canada was right to find that a serious lack of independence and impartiality should go to admissibility as well. Experts are not ordinary witnesses, testifying about facts they have personally observed and leaving the jury to form its own opinions by drawing inferences therefrom. ³⁷ The expert’s job, rather, is an exceptional one: to draw inferences for the jury in cases where jurors are unable, because of their lack of specialised knowledge, to draw appropriate inferences for themselves. ³⁸ In our view, it would be perverse to permit an expert to assist the jury in forming an opinion, in cases where it cannot help itself, if that same expert is clearly unwilling or unable to offer fair, objective and non-partisan assistance. Such experts would inevitably hinder the truth-seeking function of the court, and compromise trial fairness by offering partial, and hence inherently unreliable, evidence, which could result in a miscarriage of justice. ³⁹ The preservation of trial fairness and the enhancement of truth-seeking through the exclusion of inherently unreliable evidence are key policies underpinning many exclusionary rules of evidence, such as hearsay. Despite reluctance in Australia and the United States to consider bias as an admissibility issue, as a matter of principle judges in those jurisdictions could do so under their residual jurisdiction to exclude evidence that has greater potential for prejudice than probative value. In our view, this should occur in the circumstance of a clearly biased expert witness, for the objective benefits of their testimony would be marginal at best, while the potential for misleading the jury would be great.

By creating a narrow rule of exclusion as part of the first stage of the Mohan framework, the decision in White Burgess will streamline decisions involving clear and fundamental cases of expert bias by avoiding lengthy voir dires focused on balancing probative value against potential prejudice. All of this is for the good, and the Supreme Court of Canada ought to be applauded for dealing with this important issue in both a principled and a practical manner. ⁴⁰