What Do Judges Want from Experts?

Justice Markus Koehnen[1]
Ontario Superior Court of Justice 

Presented at the 20th Annual ACFI Fraud Conference – April 29, 2019

The title of this paper demands an immediate qualification.  I do not purport to speak on behalf of judges generally but can offer only my personal views supplemented by limited anecdotal discussions I have had with judicial colleagues.  That said, the question the title poses is capable of a relatively direct answer.  My impression of what judges want from experts is: impartiality, independence and education.  

My discussion will focus on the concept of impartiality because it has emerged as a more contentious issue in recent years.[2]  By impartiality I mean freedom from bias in favour of or against any party to the litigation.  Put another way, an expert should be indifferent to the result in the case.  The expert is there to help the court, not to help either party.  

While impartiality is capable of a simple definition, it is substantially more difficult to put into practice.  The fundamental challenge, as others have observed, is that although the litigation process demands impartiality from experts, the process has inherent structural barriers to the very impartiality it demands[3].  

I will examine this challenge in four parts. I will explore, first, why courts demand impartiality; second, the structural problems that make impartiality difficult to achieve; third, specific problems that arise out of expert evidence; and fourth I will review a short “To Do” list that may help avoid some of the challenges impartiality poses.  

I. Why Do Courts Demand Impartiality?

Experts are usually called on to provide opinion evidence. Opinion evidence is, as a rule, excluded from the court process. As a general rule, however, witnesses are not allowed to give opinion evidence.  As the Supreme Court of Canada explained the rule in White Burgess Langille Inman v. Abbott & Haliburton:

Witnesses are to testify as to the facts which they perceived, not as to the inferences — that is, the opinions — that they drew from them. ... While various rationales have been offered for this exclusionary rule, the most convincing is probably that these ready-formed inferences are not helpful to the trier of fact and might even be misleading…[4]

Experts who give opinion evidence are therefore an exception to the general rule.  Courts allow that exception to arise only when a judge or jury is unable to form an opinion about an issue because of its complexity or technical nature.[5]  So strong is the aversion to opinion evidence that some cases speak of expert evidence being “tolerated”.[6]  Since the mid-1990s there has been an unmistakable trend in the case law to tighten requirements surrounding the admissibility of expert evidence.[7]  Judges have been specifically instructed to act as gatekeepers to keep out improper expert evidence.  

The legal test to determine whether an expert’s evidence is admissible now takes place in two stages.  

In a first stage, the party that seeks to introduce the evidence must persuade the trial judge that the proposed expert opinion is: 

  1. relevant, 
  2. necessary, 
  3. not barred by any other exclusionary rule, and 
  4. given by a properly qualified expert.[8]

Evidence is relevant if it touches on an issue in the case.  Evidence is necessary if it deals with information that is likely to be outside of the knowledge and experience of a layperson.  Exclusionary rules refer to other rules of evidence like the hearsay rule which prohibits the introduction of second or third hand information as opposed to a witness testifying to what he or she personally saw or experienced.

In the second, gatekeeping stage, the party seeking to introduce the evidence must establish that the evidence is “sufficiently beneficial to the trial process to warrant its admission despite the potential harm to the trial process that might flow from the admission of expert evidence.”[9]  As Justice Doherty of the Ontario Court of Appeal described it at para. 79 of R. v Abbey[10]: 

“The "gatekeeper" inquiry does not involve the application of bright line rules, but instead requires an exercise of judicial discretion.  The trial judge must identify and weigh competing considerations to decide whether on balance those considerations favour the admissibility of the evidence.  This cost-benefit analysis is case-specific and, unlike the first phase of the admissibility inquiry, often does not admit of a straightforward "yes" or "no" answer.  Different trial judges, properly applying the relevant principles in the exercise of their discretion, could in some situations come to different conclusions on admissibility.”

The dangers of admitting expert evidence have been described as including time, prejudice, confusion, the danger a jury will be unable to make an effective and critical assessment of the evidence, the complexity of the material underlying the opinion, the expert’s impressive credentials, the impenetrable jargon in which the opinion is wrapped and the cross examiner’s inability to expose the opinion’s shortcomings.[11]  There is a risk that a jury faced with a well presented opinion may abdicate its fact-finding role on the assumption that a person labelled as an expert knows more about his or her area of practice than members of the jury do. 

Evidence of bias can be used at either one of these stages to exclude expert evidence.

I referred earlier to the tests for expert evidence having become more stringent since the mid 1990’s.  This is attributable to a series of notorious cases in Canada and elsewhere.  Two of the most infamous Canadian examples involved Dr. Charles Smith and the Motherisk program at Toronto’s Hospital for Sick Children.  Dr. Smith was a forensic pathologist.  A number of parents were wrongfully convicted of killing their children based on his expert evidence.  A subsequent judicial inquiry revealed that Dr. Smith believed it was his job to help the Crown secure a conviction as opposed to helping the court in an impartial manner.  A closer review of his evidence revealed that he regularly testified beyond the scope of his true expertise.  While the Motherisk program did not result in any convictions, it resulted in a string of parents losing custody of their children to social service agencies based on expert scientific evidence which purported to demonstrate that the parents were drug users. A subsequent judicial inquiry established that the tests were unreliable; the parents were not drug users; and the parents should never have been deprived of their children.  As a result of these and other cases, courts have taken a considerably more muscular approach to excluding expert evidence, limiting its use and critically assessing its reliability if admitted.

Although the consequences of opinion evidence by financial experts rarely leads to jail time and even more rarely, if ever, leads to social service agencies taking children from parents, the greater skepticism with which judges view experts has also been applied to financial experts.  This greater skepticism towards financial experts has led to adverse judicial comments about individuals who do not demonstrate impartiality.  A few examples from recent cases make the point:

“It is shocking to me that two reputable appraisers, taking their duties as experts seriously, namely to be independent and uninfluenced by the party who retained them, could come to such different conclusions, using essentially the same approach and methodology for each of these two comparables.  I find it suspect when each appraiser’s opinion so clearly aligns with the interests of the party who hired him.  While I recognize that valuation is an art, not a science, I would have expected the ultimate opinions to have been much closer to one another.”[12] 
“[Names of plaintiffs’ experts] describe themselves as forensic accountants.  They have experience and qualifications in matters of financial reporting and disclosure, GAAP and accountants’ negligence.  In the course of their reports, however, they repeatedly purport to give opinions on matters outside their proven expertise, including matters of corporate governance and securities law. … [Name of expert] has no proven qualifications to opine on governance principles or securities law, even if evidence of the latter was admissible, which it is not.”[13]
“The willingness of an expert to step outside his or her area of proven expertise raises real questions about his or her independence and impartiality.  It suggests that the witness may not be fully aware of, or faithful to, his or her responsibilities and necessarily causes the court to question the reliability of the evidence that is within the expert’s knowledge.”[14]
[Expert’s name] engaged in blatant advocacy, making exaggerated, inflammatory and pejorative comments and innuendos, which were argument rather than evidence[15].
[Name of defence expert] acknowledges that an expert’s approach to the issue of auditors’ negligence should not vary depending on the side for which he is called to testify; but I was disappointed to learn that he did not adopt that even – handed approach in the instant action.  …[This] negatively impacted his credibility and usefulness as an “independent” expert[16].

Your credibility is all you have as an expert witness.  A judge or jury has difficulty making decisions about technical areas in which they have no expertise.  That is why you are there.  No matter how solid your technical arguments, if they are tainted by lack of impartiality, your evidence will be rejected as unreliable even if it passes the formal test of admissibility.  Getting your evidence admitted simply means that the trial judge or jury will hear it. It does not mean they will believe it.    

Bias in your evidence is fatal for two reasons.  First, it can lead you to lose the case for the party that retained you.  In Gould v. Western Coal Corporation, the plaintiffs needed leave of the court to bring a claim for secondary market misrepresentation under the Securities Act.  That application turned on expert evidence.  The judge rejected the plaintiffs’ application for leave in large part because he rejected the evidence of their expert:  

[The plaintiffs’ expert] is severely compromised by his failure to stick to matters within his expertise, by engaging in impermissible fact-finding and by becoming an advocate on behalf of his client, rather than an impartial expert seeking to assist the court. [His] exaggerated and speculative assertions only serve to undermine his credibility and independence. In light of these infirmities, I have no confidence whatsoever in his evidence and there is no reasonable possibility that his evidence will be accepted at trial.[17]

Second, a finding of bias discourages future retainers.  Almost all Canadian reasons for judgment on any material issue are available on CanLII, a free, fully searchable website to which anyone with a web browser has access.  It takes only seconds to find what a judge has said about you in an earlier case.  Rest assured that the party on the opposite side of you in any lawsuit will take those few seconds.  If a judge has made adverse comments about your evidence, the party opposite will find some way of getting that in front of the judge or jury in any future case in which you testify.  Anyone considering hiring you will do a similar search.  You need not be a financial expert to connect the dots.

II. What Makes Independence and Impartiality so Difficult to Achieve?

Now if bias loses the case and impedes future retainers, the solution seems simple:  just be impartial.  Yet people continue to fall afoul of the requirement for impartiality.  Are they simply “bad people”?  Probably not. 

The difficulty is that there are fundamental structural issues with the way experts are retained and used in an adversarial litigation system that makes impartiality difficult to maintain even for those operating on the highest ethical plane.

These issues were canvassed by Justice David Paciocco, in “Unplugging Jukebox Testimony in an Adversarial System:  Strategies for Changing the Tune on Partial Experts[18]  Justice Paciocco now sits on the Ontario Court of Appeal and is one of Canada’s leading evidence scholars.  He identifies five psychological biases that can inadvertently taint an expert’s impartiality.

The first is selection bias.  Selection bias arises the first time you even speak with someone about a retainer.  The unspoken understanding from the first phone call is that the lawyer looking for an expert will only hire someone who supports the position the lawyer is advancing.  In some sorts of cases experts are clearly divided as ones who testify only for the plaintiff or only for the defence.  Even if you do not fall under that category or are being hired for a case that does not fall into the basket of litigation characterized by this problem, you know from the get-go that your retainer depends on providing an opinion that supports the position of the party contacting you.

Second is association bias.  Association bias arises from the natural human tendency to be helpful.  We all want to help those who ask for our assistance let alone to those who employ and remunerate us.  

Third is confirmation bias; the tendency to “process information by looking for, or interpreting information that is consistent with one’s existing beliefs.”[19] It often leads us to ignore inconsistent information.  The more the area is subject to interpretation, the greater the danger of interpreting to find what we are looking for.

Fourth is professional bias.  An expert who regularly testifies for one type of litigant has a vested financial and personal self-interest in continuing down that path.  The financial self-interest is obvious:  no one wants to see a steady stream of revenue dry up.  The personal self-interest is slightly less obvious:  there is a natural human reluctance to turn one’s back on views and opinions one has held for years.

Fifth and finally, is noble cause distortion.  This is the bias that arises from believing that you are “on the side of good.”[20]  While accountants in civil litigation will rarely view themselves as being in the same position as pathologists convicting “child killers” or scientists protecting children from “abusive parents,” they are nevertheless subject to their own forms of noble cause distortion.  The lawyer who retains you has a mandate to pursue zealously the interests of his or her client.  The lawyer is not meant to be impartial.  As a result, the adversarial system leads many lawyers to “believe,” at least to a degree, in the right of their client’s cause.  The lawyer’s communication with you risks being influenced by his or her mandate.  There is a substantial risk that the lawyer will not be communicating with you in a truly unbiased manner.  I would venture to say that the opposite is far more likely the case.  In addition, financial experts are intelligent people with an interest in their field.  That inevitably leads them to have policy views about a variety of issues.  Some may espouse particular social, economic or professional views about the degree of disclosure required in financial statements, the manner in which to apply particular accounting principles, the prevalence of fraud and so on.  Such views inevitably affect the opinions you advance and may impact your impartiality. 

Anyone or more of these biases creates a risk of allowing partiality to creep into one’s approach to an issue without becoming aware of it. 

III. Specific Problems Arising out of Expert Evidence

Let me turn now to some of the common issues that raise concerns about an expert’s impartiality. 

(i) Testifying Outside of Area of Expertise

By far the most common issue is the expert who testifies outside of his or her scope of expertise.  The first stage of your evidence in court will be one that qualifies you to testify as an expert in a particular area.  The lawyer calling you asks you questions about your education and experience to build up your credibility and then “tenders” or presents you as an expert with respect to particularly defined issues or in a particularly defined field.  

Given that the role of an expert is to assist the court, experts who testify to issues outside of their area of expertise are, by definition, not assisting the court because they are speaking to matters in respect of which they are not qualified to evidence.  An expert who does so is immediately viewed with scepticism.  

This issue of scope of expertise arises at various junctures in your relationship with the lawyer who retains you.  

First, the initial contact.  Everyone called about a potential retainer would obviously like to get the retainer.  That may lead some to characterize their expertise as being suitable for the assignment.  There can be a tendency to reframe the issue as the lawyer describes it into an issue that falls more closely within the expert’s area of specialization.  That will likely lead to an unsatisfactory outcome.  In a best case scenario the lawyer will notice the issue when he receives your report. In a worst case scenario the characterization will appear for the first time when you are cross-examined at trial.  You will certainly have an unhappy client and potentially an unhappy judge.  Be honest about your area of expertise and remain squarely within it, even if it means declining potential retainers.

It is, however, much easier than you might think to drift into evidence outside of your area of expertise, especially if you have more broadly-based policy interests.  Recall the earlier example of the accountant with expertise in GAAP, financial reporting and disclosure.  He was criticized for, among other things, testifying about issue of corporate governance.  Accountants or auditors may have strongly held views about corporate governance that arise from their exposure to governance issues that arise out of interactions between auditors and clients.  They might in fact have fairly deep experience with governance as it relates to audit issues.  Those experiences can lead an auditor to stray off of pure audit issues and into governance issues.  

This risk underscores the importance of focussing carefully on the definition of your expertise.  Counsel often leave as an afterthought, the precise definition of your expertise rather than bringing laser sharp focus to it.  Returning to our accountant with views on governance, if the accountant had been properly qualified as an expert on corporate governance issues affecting audits there would be no difficulty with the auditor testifying about corporate governance.  This speaks to the need to think carefully about exactly what the report says and exactly what the expert will testify about during examination in chief to ensure that the expert is qualified in each of those areas.  Keep in mind that expertise can be established through research or experience.  Thus, an auditor who may have no formal credentials with respect to corporate governance but who has spent decades experiencing corporate governance as it affects audits may well be qualified to testify about it.  It is the failure to anticipate that potential extension of expertise that can cause the problem. 

(ii) Partisan Language

The language contained in your report and the language you use when testifying may also tend to suggest bias.  Not only does inflammatory language deprive you of a sense of impartiality but so does language that tends towards absolutism or that expresses a view about an opposing party’s motivation.  Motivation is unlikely to be within an accountant’s area of expertise.  Specific examples of language that might tend to suggest bias on the part of the writer include expressions like:

  • No reasonable person would (followed by what the opposing party did);
  • particular conduct is consistent with… 
  • … is suspected or I suspect…
  • … appears to be unusual
  • … Could be (followed by a statement of negative conclusion)
  • …  Speaking about the state of mind of someone other than yourself (for example a concern of the reader of a financial statement)

While there are circumstances in which these sorts of expressions may be appropriate, they should cause you to pause and ask yourself: 

  • Is it true in the strictest sense of the term that no reasonable person would ever do a particular thing?
  • Is the conduct also consistent with something other than the negative conclusion you are suggesting? 
  • Are you truly giving an opinion based on knowledge and experience or are you speculating about what someone else might think or speculating about why someone else might do something?

It may well be that you do have knowledge and experience that qualifies you to speak about someone else’s motivations or thoughts.  If such is the case, it is important to explain why you do in fact have insight into the motivations or state of mind of others so as to remove such statements from the realm of speculation and elevate them to the realm of informed opinion.  

(iii) Cherry Picking

Cherry Pickingis the selective choice of information, or approaches to an issue that lead an expert to favour the party that retained him or her.[21]  While no one single instance of cherry picking may sway the opinion, a series of choices can easily do so.  The danger cherry picking is that it is often unconscious.  It can be the product of confirmation bias; the tendency to absorb and focus only on information that confirms our own views.  It is ripe fodder for cross-examination and imposes serious challenges to the expert’s reliability and credibility.

Cherry picking can lead an expert to ignore contradictory facts or approaches.  It can also lead an expert to sugar coat problems when communicating with their retaining counsel.  It is important to be direct, frank and candid with the lawyer retaining you about any difficulties in the case.  If there are limitations on the sort of opinion you can give or if you are equivocal about the sort of opinion you can provide, you retaining lawyer must know about them.  This is not the time for sugar coating or indirect language.  Implications of what you are saying may be obvious to you as someone schooled in the field. They will not necessarily be obvious to the lawyer retaining you.  Leave nothing unsaid or to be implied when giving your retaining lawyer any “bad news” make sure he/she understands it fully.  The lawyer will be making strategic decisions going forward based on your views.  If he or she does not fully understand the limitations on those views, you are preventing them from making the appropriate strategic decisions.

(iv) Critique Reports

Critique reports are reports that do not offer an opinion themselves but simply critique an opposing expert.  Courts are inherently suspicious of such reports.  It is easy to critique the work of another without having to take a position on the issue yourself.  It is easy to critique someone else’s work even if you fundamentally agree with it.  Courts have recognized these frailties and tend to give little weight to such reports.[22]  There have however been limited carve outs for critique reports that critique the methodology of another expert.[23]  As a general rule, experts should treat such retainers with caution and ensure that there is a specific reason for which they cannot provide their own opinion on the merits.

(v) Intellectual rigidity

Judges tend to work in nuances.  It is rare that a judge faces an issue that is either black or white or that is capable of a bright line delineation.  More often than not, a judge is faced with the question of where, on a spectrum of various shades of grey, a particular case should be placed.  Experts who take a rigid right versus wrong view of an issue tend to be viewed with scepticism.  Such views are all the more suspicious in experts because they have only limited information.  Experts’ reports are based on assumptions, even minor changes in which can lead to different analytical outcomes.  An expert who refuses to appreciate this is likely to be found to be unreliable.  Characteristics of such experts include:  asserting bald, conclusory positions without explaining why that position is the correct one; using overly definitive or pejorative language such as ridiculous, impossible, no reasonable person and so on; and refusing to modify or moderate their opinions when faced with competing views or changed factual assumptions.

(vi) Ghost Writing

An issue of emerging concern is that of ghost written expert reports.[24]  Ghost written reports are those written, not by the testifying expert but by a member of his or her staff.  While the issue has emerged most acutely in reports stemming from medical examinations, it also has relevance to financial experts.  

The process of drafting a report influences your views.  As you work directly with the evidence, you develop and refine your views; you bring nuance to the analysis.  A report written solely by another person, about which you then testify as the “senior expert,” runs the potential of losing that nuance.  This is not to say that you cannot delegate certain tasks to more junior members of your staff or be assisted by others, but it does mean that the testifying expert should continue to hold the ultimate pen.  Put another way you can delegate tasks but not judgement.  

(vii) Contradicting Previously Expressed Views 

An expert who, in his opinion, contradicts positions he or she has taken in the past without having an easily comprehensible reason for the difference of view, is bound to be seen as biased.  You should assume that the opposing party will have poured over anything you have published or presented to look for the expression of views that contradict those you are voicing in the case at hand.  Even more dangerous is the opponent who pours over court files to search for opinions you have given in other cases.  If in another case, you have taken a view that contradicts the approach you are taking in the case at hand, you face a serious challenge to your credibility.  

(iv) Impartiality To Do List

To decrease the risk of being singled out for criticism in a judge’s reasons, I offer the following modest To Do list:  

  1. Be direct, frank and candid with your retaining lawyer about any limitations on your expertise and any “bad news” about the case.  
  2. Provide, in your report, all of the reasons for which you came to the opinion you did.  Leave nothing implied or unspoken.
  3. Ensure you are qualified as an expert in a way that allows you to speak about all of the reasons on which your report is based.
  4. Ensure you are providing your true opinion, not arguments to help your retaining lawyer.  
  5. Assume the trier knows nothing about your area of expertise.  Use simple direct language in your report and when testifying.
  6. Remove all pejorative, inflammatory or overly definitive language.  Removing adverbs and adjectives is a good place to start.
  7. Ensure your approach and methodology is consistent with past publications, presentations and reports.  If it is not, ensure you have an easily comprehensible reason for the difference.
  8. Review your factual assumptions and approaches for cherry picking.  If there are different approaches, address them and explain why they are not appropriate.  Be candid about how they would affect your view.
  9. Would your opinion would be the same if the opposing party had retained you?  
  10. Don’t argue the case as a witness.  Concede points when appropriate if given changed assumptions.


By far the greatest attribute of an expert witness is that of impartiality.  Judges and juries are genuinely looking for help to deal with complex, technical issues.  They are not looking for advocates.  An expert who offers help, not advocacy, will have and retain authority in the court room.  

Although I cited earlier several examples of courts that criticized experts for lack of impartiality, the good news is that courts also recognize and appreciate experts who are impartial.  Just as courts openly criticize experts who are biased, they also praise experts who demonstrate impartiality:

Mr. Carlucci was an excellent witness.  His analysis was methodical and logical.  He did not hold on to positions if he was successfully challenged on them.  Mr Carlucci’s demeanor suggested he had no personal interest in the outcome of the case; rather, his role was to analyse where the trust funds had gone, and advise the court.  He did.  I accept his analysis and opinion.[25]

I hope some of the foregoing suggestions will help you avoid being criticized for your approach and instead have you singled out for excellence.  


[1] I am greatly indebted to Patrick Harris, a law clerk at the Ontario Superior Court of Justice for his research assistance.

[2]  That said, I will explain briefly the concepts of independence and education.  By independence I mean the ability to be free of financial or psychological pressure from the party retaining you.  Simply receiving a fee from the party that retains you will not compromise independence. An ongoing relationship with the party that retains you may.  Similarly, compensation that depends on the result in the case compromises independence.  In a similar vein, a family connection with a party to the case or the lawyer retaining you would also compromise independence.  By education I mean the ability to educate a judge or jury about matters that can appear complex and technical to the layperson.

[3] 2015 SCC 23 at para. 14.

[4] R. v. Mohan, [1994] 2 S.C.R. 9

[5] R. v. D.D, 2000 SCC 43 at paras. 51, 56.

[6] 2015 SCC 23 at para. 14.

 [7] R. v. Mohan, [1994] 2 S.C.R. 9

[8] R. v. D.D, 2000 SCC 43 at paras. 51, 56.

[9] R. v. Abbey, 2009 ONCA 624 at para. 76

[10] 2009 ONCA 624

[11] Abbey at para. 90.

[12] Plese v. Herjavec, 2018 ONSC 7749 at para. 108

[13] Gould v. Western Coal Corporation, 2012 ONSC 5184 at para 82

[14] Gould v. Western Coal Corporation, 2012 ONSC 5184 at para 85

[15] Gould v. Western Coal Corporation, 2012 ONSC 5184 at para 89

[16] Livent Inc. v. Deloitte & Touche, 2014 ONSC 2176 (Ont. S.C.J.)

[17] 2012 ONSC 5184 at para 261

[18] 34 Queen’s L.J. 565 (2008-09)

[19] Encyclopedia Britannica: confirmation bias

[20] Paciocco at p. 582.  

[21] James McAuley:  The Expert Accountant in Civil Litigation 2d ed. , LEXISNEXIS at page 368

[22] M v. F, 2015 ONCA 277; Christoforou v. John Grant Haulage Ltd., 2016 CHRT 14

[23] Halton Children’s Aid Society v. A.W.,  2016 ONCJ 358 

[24] Jennifer Hunter, Expert Evidence for Litigators,  Law Society of Ontario October 29, 2018 at page 2-4

[25] Plese v. Herjavec 2018 ONSC 7749 at para 60.