How and When to Safeguard the Independence of the Expert

By Katherine L. Shadbolt
janvier 6, 2022

This paper highlights cases where an Ontario Court held that expert evidence was not admissible for not meeting the test set out in White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 SCC 23 (“White Burgess”). It will:

  1. review the test for admissibility as set out in White Burgess;
  2. discuss four subsequent and notable Ontario cases where expert evidence was not admitted; and
  3. provide practical tips on how Counsel can safeguard the independence of the expert.


In White Burgessat paras 23-24, the Supreme Court of Canada provided clarity and guidance regarding admissibility of expert evidence. Cromwell J., writing for the Court, adopted the two-step approach in R. v. Abbey, 2009 ONCA 624with minor adjustments:

  1. “At the first step the proponent of the evidence must establish the threshold requirements of admissibility.” These are the four traditional “threshold requirements” established in R. v. Mohan, [1994] 2 SCR 9: 1) relevance; 2) necessity in assisting the trier of fact; 3) the absence of an exclusionary rule; and 4) a properly qualified expert. And, “in addition, in the case of an opinion based on novel or contested science or science used for a novel purpose, the reliability of the underlying science for that purpose…”
  2. The second component is a “discretionary gatekeeping step” where the “judge balances the potential risks and benefits of admitting the evidence in order to decide whether the potential benefits justify the risks.” It is a cost-benefit analysis where the Court must determine whether the expert evidence should be admitted because its probative value outweighs its prejudicial effect.

As Cromwell J. observed, at para 33, “there is a broad consensus about the nature of an expert’s duty being to the Court. There is no such consensus, however, about how that duty relates to the admissibility of an expert’s evidence.” This raised two important questions in White Burgess namely “should the elements of this duty go to admissibility of this evidence rather than simply to its weight? And, if so, is there a threshold admissibility requirement in relation to the independence and impartiality?”

Cromwell J. confirmed, at para 40, that the potential bias of an expert must be considered in the admissibility of the expert’s testimony at the initial threshold inquiry and once that threshold is met, it must also be considered as the Court exercises its gatekeeping role and its discretion to exclude evidence.

In other words, as Cromwell J. described, at para 2: “Expert witnesses have a special duty to the Court to provide fair, objective and non-partisan assistance. A proposed witness who is unable or unwilling to comply with this duty is not qualified to give expert opinion evidence and should not be permitted to do so.”


Since White Burgess, Ontario Courts have discussed why expert evidence should be rejected for failing to satisfy the test for admissibility set out above in at least four significant cases.

In Bruff-Murphy v. Gunawardena2017 ONCA 502 (“Bruff-Murphy”)the Court of Appeal found that the trial judge should have excluded the expert’s testimony for the defence because the expert crossed the line from an objective witness to an advocate for the defence. Despite his concerns, the trial judge did nothing to exclude the opinion evidence or alert the jury about the problems with the expert’s testimony.

The Court of Appeal, at para 2, specifically noted that:

“…Appellate courts have repeatedly instructed trial judges that they serve as gatekeepers when it comes to the admissibility of expert opinion evidence. They are required to carefully scrutinize, among other things, an expert witnesses’ training and professional experience, along with the necessity of their testimony in assisting the trier of fact, before the expert is qualified to give evidence in our courts….” (Emphasis added.)

In ordering a new trial, at para 5, the Appellate Court noted that, had the trial judge properly discharged his gatekeeper duty at the qualification stage, “…he would have concluded that the risks of permitting the expert to testify far outweighed any potential benefit from the proposed testimony.” In addition, the expert crossed the boundary of acceptable conduct and descended into the fray as a partisan advocate during his testimony. In these circumstances, the trial judge failed to fulfill his ongoing gatekeeper function and exclude in whole or in part the expert’s unacceptable testimony. As the trial judge did not fulfill an ongoing gatekeeping role, the Appellate Court, at para 6, held that trial fairness was irreparably compromised.

As noted in the Bruff-Murphy, the trial judge must be vigilant in determining whether the expert meets the first component of the test set out in White Burgess – namely, does the evidence meet the threshold of admissibility. However, even if the first part of the test is met, it is still possible that the expert will be subsequently disqualified; part of the trial judge’s ongoing residual discretion is to exclude prejudicial evidence. This is an ongoing discretion that must be exercised throughout the trial.

In reviewing why the expert evidence was not allowed, in Bruff-Murphy, the following are notable examples of how the expert compromised his independence:

  1. The expert attacked the accused’s credibility by making comments in his report of instances where the accused gave him certain information, and this information contradicted what he later found in her medical records. Counsel for the defence submitted that this exercise did not meet the test in Browne v. Dunn, (1893) 6 R 67 (U.K. H. L.) as it did not give the accused the opportunity to explain any inconsistencies.
  1. The expert’s comments about the witness’s credibility were close to the task of the jury.
  2. The expert testified that he discarded any notes he may have made during his interview with the accused. He therefore did not have supporting documentation for a number of his comments.
  3. He appeared biased, only considering one side of the story.
  4. His methodology was questionable. The vast majority of the expert’s evidence was not of a psychiatric nature which was his speciality of expertise. Instead of staying within the bounds of his expertise, which was to provide an independent assessment of the accused’s psychiatric condition, he recited inconsistencies between what the accused said in an independent medical examination and what her medical records revealed.

In a second case, Pentalift Equipment Corporation v. 1371787 Ontario Inc., 2019 ONSC 4804 (“Pentalift”), the expert witness’s evidence was rejected by the trial judge, almost in its entirety, as he did not critically question any of the information provided to him by the client retaining him. Therefore, he lost his objectivity because he was too aligned with the client’s wishes. The expert also did not follow or apply the standard methodology in preparing his report, and took a number of “shortcuts” to meet his client’s time deadline (at para 89).

In a third case, Parliament v. Conley and Park, 2019 ONSC 3995 (“Parliament”), one expert witness was rejected based on bias. The physician for the defence was biased as she did not consider the opposing party or the Plaintiff’s version of events. At times, she refused to acknowledge that there was another possible version of the facts. In fact, she “high-handedly” rejected the Plaintiff’s evidence without offering any semblance of an explanation (at para 36).

On appeal, in Parliament v. Conley, 2021 ONCA 261, at para 2, the Plaintiffs argued that another expert, the only expert on the standard of care for the Respondents (a different physician than the one mentioned above), gave evidence that went beyond the scope of his expertise, failed to demonstrate impartiality, and usurped the jury’s proper role in opining on credibility and some of the factual questions. The Court of Appeal specifically noted, at para 51, that one of the dangers of experts who give evidence that oversteps their boundaries is “the risk that a jury, faced with difficult issues of credibility and reliability and a well-presented expert opinion, will abdicate its fact-finding role on the understandable assumption that a person labelled as an expert by the trial judge knows more about his or her area or expertise than do the individual members of the jury…there was a risk that the members of the jury would accept Dr. Bruce’s credibility and reliability assessments, rather than assess the evidence of the witnesses and reach their own conclusions.”

As the trial judge did not instruct the jury to disregard the expert’s evidence in relation to the credibility and reliability of two doctors and a third person in her charge, the Court found there was a miscarriage of justice that justified a new trial: at paras 67-71.

The Court of Appeal in Parliament v. Conleyat para 70, quoted from Bruff-Murphyat para 72: “[t]his Court has a responsibility to protect the integrity of the justice system. This is not a ‘no harm, no foul’ situation.” It further noted as follows, at para 47: “The continuing gatekeeper role of a trial judge includes the continuation of the residual discretion to exclude evidence when they are not satisfied that the testimony’s probative value exceeds its prejudicial effect.”

In a fourth case, Barker v. Barker, 2019 ONSC 5906 (“Barker”), the expert witness for the defence was biased in favour of the Defendants. Although the expert was skilled and respected in his field, his professional association with the very institution whose programmes were being criticized by the Plaintiffs resulted in his disqualification. The trial judge found, at para 30: “The probative value of his report and potential testimony is rather low since his objectivity as an expert is in serious doubt; that, in turn, makes the prejudicial value of his evidence substantially higher than the probative value and effectively disqualifies him from giving expert evidence at trial.”

In these four cases, it is important to note when the expert witness’s testimony was rendered inadmissible. In each case, it was either at trial or appeal as follows:

  1. In Bruff-Murphy, it was at the appeal when the Court of Appeal found that the trial judge failed to properly discharge his gatekeeper duty at the qualification stage of the defence’s expert. The Court allowed the plaintiff’s appeal and ordered a new trial as a result.
  2. In Pentalift, it was not until the expert was cross-examined at trial that all the deficiencies in his report came to light. The trial judge rejected the defence’s expert’s evidence almost in its entirety.
  3. In Parliament, in the context of a voir dire at trial, without the jury, the trial judge

allowed the plaintiff’s motion to disqualify a physician tendered by the defence. On the appeal, a new trial was ordered as the sole witness for the respondents on the issue of standard of care exceeded the admissible scope of his evidence in a way that was highly prejudicial to the appellants. A new trial was ordered at the appeal.

  1. In Barker, as a result of a mid-trial motion, in which the Plaintiffs opposed the

qualification of one of the Defendant’s proposed witnesses, the trial judge found that the proposed witness should be disqualified as an independent witness.

As it is often not until the trial stage, and in two cases at the appeal level, that expert evidence is rejected, the cost and prejudice to a party who has retained an expert at the initial stages of an action, or during the action, only to find out at the end of the proceeding that the expert’s testimony is disqualified or not allowed, in whole or in part, is very costly.


What are the implications for Counsel when an expert is disqualified? In Pentalift, the trial judge rejected most of the expert’s testimony and then admonished Counsel, as follows, at para 97:

“… counsel have an obligation to ensure that an expert understands his or her unique role in a trial and that they are there to assist the Court and to prepare the witness for testimony. This, of course, is to be distinguished from any interference with the substance of the expert’s opinion, which must be his or her independent analysis and conclusion.”

Given these remarks and the case law that has evolved since White Burgess, there is an onerous responsibility on Counsel to select and choose an independent expert who understands and accepts their duties.

There is an ongoing obligation to prepare that witness for testimony to assist the trier of fact. As was observed by Justice Tzimas in the Pentalift case, at para 98, who reviewed and cited Justice Paciocco’s article, “Unplugging Jukebox, Testimony in an Adversarial System: Strategies for Changing the Tune on Partial Experts” (2009) 34 Queen’s L. J. 565 at 600-608, Counsel should be reminded to guard against:

  1. Selection bias (why the expert is chosen);
  2. Association bias (whether the expert might demonstrate a desire to do something serviceable for his or her own customer/ employer);
  3. Professional bias (whether an expert might be defending his or her own research or own credibility);
  4. Noble cause distinction (whether the expert might demonstrate a willingness to distort evidence, believing that he or she is on the side of good); and
  5. Dogmatism and rigidity.

Any one or more of these flaws will render the expert’s views unreliable and useless. When Counsel fail to guard against these risks, they run the risk of bringing the administration of justice into disrepute.

After reviewing the case law and the points above, it bears emphasizing that Counsel should:

  1. Ensure that the expert has the requisite credentials for the mandate requested and the scope of the task.
  2.  Ensure that the expert has the time to properly prepare a report and provide an opinion.
  3. Reinforce with the expert that they should not take shortcuts and that they follow the standard methodology as required in their profession.
  4. Provide specific instructions that form the expert’s retainer, and ensure that the expert’s report is on point, with no tangents or issues addressed that the expert is not qualified to address.
  1. Make sure that the expert has all the salient facts.
  2. In preparing the expert to testify at trial, emphasize again that the expert’s testimony must be relevant and necessary in assisting the trier of fact.
  3. Know where the onus or burden lies regarding a lack of independence / bias of an expert witness. As explained in Parliament SCJ, at para 16, citing to White v Burgess, the party opposing the admission of the expert evidence has the burden “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 [their] duty.…Once a realistic concern is shown, the party seeking to have the expert admitted has the burden to establish on a balance of probabilities that the expert should nonetheless be allowed to give evidence.”
  4. When dealing with an opponent’s expert, continue to ask about draft reports and about the expert’s assumptions used (and substantiation of same) on cross-examination. Cross- examination remains one of the best tools to undermine expert’s reports that are not independent or are not factually correct.

I hope these practical tips are of assistance and enable lawyers to avoid the consequences of having an expert disqualified at trial or on appeal. At the trial stage, or the appellate level, it is probably too late to do any remedial work.


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