Summary on Flawed Expert Evidence
1. The leading authority on admissibility of expert opinion evidence at common law in Canada, R. v. Mohan, 1994 SCC 80, has been inadvertently misread and misapplied for more than 30 years.
2. Mohan has been uniformly cited as the authority for the perilous proposition that "there is no longer a general bar against expert opinion evidence on the ultimate issue in a case." However, the fulsome and accurate reading of Mohan, within its precise factual context, is that "there is no longer a general bar against expert opinion evidence on the ultimate issue of fact in a case."
3. There is no decision by the Supreme Court of Canada holding that an expert may offer opinion evidence on an issue of mixed law and fact. To the contrary, there have been decisions and statements of law below which were upheld or quoted with approval by the Supreme Court that expert opinion evidence on an issued of mixed law and fact is not permissible (see R. v. Fisher, and R. v. Graat decisions, supra, in the Supreme Court and the Ontario Court of Appeal).
4. This error of misreading or over-generalizing Mohan has led to transformational adverse consequences. The error allows evidence on two types of ultimate issues (namely issues of fact, and issues of mixed law and fact) to be eligible for further assessment for admissibility under the Mohan - White Burgess test, instead of only ultimate issues of fact alone. The error introduces arbitrariness in expert evidence and therefore undermines reliability of, and access to, justice throughout Canada.
5. In conclusion, the correct framework is that in addition to the Mohan - White Burgess test for admissibility of expert evidence at common law in Canada, there ought to be a preliminary assessment to reject expert evidence on an issue of mixed law and fact. In the result, there are two stages to control expert opinion evidence: (1) Does the proposed evidence involve a question of fact only? If no, it is rejected for being outside the scope of expert opinion evidence; and (2) If yes, it may then proceed to be further assessed under the Mohan - White Burgess framework before admission as expert opinion evidence.
1. The leading authority on admissibility of expert opinion evidence at common law in Canada, R. v. Mohan, 1994 SCC 80, has been inadvertently misread and misapplied for more than 30 years.
2. Mohan has been uniformly cited as the authority for the perilous proposition that "there is no longer a general bar against expert opinion evidence on the ultimate issue in a case." However, the fulsome and accurate reading of Mohan, within its precise factual context, is that "there is no longer a general bar against expert opinion evidence on the ultimate issue of fact in a case."
3. There is no decision by the Supreme Court of Canada holding that an expert may offer opinion evidence on an issue of mixed law and fact. To the contrary, there have been decisions and statements of law below which were upheld or quoted with approval by the Supreme Court that expert opinion evidence on an issued of mixed law and fact is not permissible (see R. v. Fisher, and R. v. Graat decisions, supra, in the Supreme Court and the Ontario Court of Appeal).
4. This error of misreading or over-generalizing Mohan has led to transformational adverse consequences. The error allows evidence on two types of ultimate issues (namely issues of fact, and issues of mixed law and fact) to be eligible for further assessment for admissibility under the Mohan - White Burgess test, instead of only ultimate issues of fact alone. The error introduces arbitrariness in expert evidence and therefore undermines reliability of, and access to, justice throughout Canada.
5. In conclusion, the correct framework is that in addition to the Mohan - White Burgess test for admissibility of expert evidence at common law in Canada, there ought to be a preliminary assessment to reject expert evidence on an issue of mixed law and fact. In the result, there are two stages to control expert opinion evidence: (1) Does the proposed evidence involve a question of fact only? If no, it is rejected for being outside the scope of expert opinion evidence; and (2) If yes, it may then proceed to be further assessed under the Mohan - White Burgess framework before admission as expert opinion evidence.
A Vaccine Against the Disease of Expert Opinionitis in Canada
For those in the trenches of legal warfare involving expert opinion evidence in Canada, it is an open secret that there is virtually no expert evidence money cannot find. In many areas of law, cases frequently feature several experts on each side with predictable and conclusory legal opinions.
As the law permits, and therefore effectively requires, lawyers to tender legal opinions on questions of mixed law and fact the experts happen to have, that is in our submission the principal cause of why the disease of "expert opinionitis" has been thriving largely unabated in Canada for at least 30 years since R. v. Mohan, 1994 SCC 80 CanLII.
A vaccine against the oft quoted Mohan appears promising to challenge and conquer the disease. The relatively new s. 52(1) of the Constitution Act, 1982 in our view offers the challenger an express, constitutionally supreme remedy available to a trial court to nullify the apparent unconstitutional law by the Supreme Court of Canada in Mohan, namely that there is generally no bar against expert legal opinion evidence on even ultimate issues of mixed law and fact, on the grounds that such law both abdicates judicial responsibility and contravenes legislative power under the Constitution Act, 1867.
The status quo under Mohan fosters intolerable risks of miscarriages of justice induced by legal opinions experts "happen to have", an ominous description from the regrettably preventable inquiry report by the Honourable Justice Stephen Goudge (Vol. 1, p. 18) on the preventable miscarriages of justice involving Dr. Charles Smith. It also profoundly impairs access to justice throughout the country by requiring new, and diverting existing, scarce resources from all stakeholders to entertain innumerable engagements with arbitrary opinion evidence, implicating all areas of law and justice.
For those in the trenches of legal warfare involving expert opinion evidence in Canada, it is an open secret that there is virtually no expert evidence money cannot find. In many areas of law, cases frequently feature several experts on each side with predictable and conclusory legal opinions.
As the law permits, and therefore effectively requires, lawyers to tender legal opinions on questions of mixed law and fact the experts happen to have, that is in our submission the principal cause of why the disease of "expert opinionitis" has been thriving largely unabated in Canada for at least 30 years since R. v. Mohan, 1994 SCC 80 CanLII.
A vaccine against the oft quoted Mohan appears promising to challenge and conquer the disease. The relatively new s. 52(1) of the Constitution Act, 1982 in our view offers the challenger an express, constitutionally supreme remedy available to a trial court to nullify the apparent unconstitutional law by the Supreme Court of Canada in Mohan, namely that there is generally no bar against expert legal opinion evidence on even ultimate issues of mixed law and fact, on the grounds that such law both abdicates judicial responsibility and contravenes legislative power under the Constitution Act, 1867.
The status quo under Mohan fosters intolerable risks of miscarriages of justice induced by legal opinions experts "happen to have", an ominous description from the regrettably preventable inquiry report by the Honourable Justice Stephen Goudge (Vol. 1, p. 18) on the preventable miscarriages of justice involving Dr. Charles Smith. It also profoundly impairs access to justice throughout the country by requiring new, and diverting existing, scarce resources from all stakeholders to entertain innumerable engagements with arbitrary opinion evidence, implicating all areas of law and justice.
Inconsistency in the Jurisprudence on the Scope of Expert Opinion Evidence
1. Over the past generation, while the rules at common law on admissibility of expert opinion evidence have generally become more rigorous, there remains a foundational question which has not received direct guidance by the Supreme Court of Canada, namely, “Does the proper scope of expert evidence extend beyond the fact-finding process and a question of fact to include (legal) opinions on a question of mixed law and fact?”
2. Currently, jurisprudence on expert evidence makes little distinction between opinion evidence on issues of fact and issues of mixed law and fact. The admission process generally is to direct nearly all proposed expert evidence to the Mohan – White Burgess gate and see what will pass, regardless of whether it is legal opinion evidence from a former judge to advise a sitting judge on what law and interpretation to apply to the facts of the case, written “in a form that would easily translate into reasons for judgment” (Walsh v. BDO Dunwoody LLP, 2013, BCSC 1463 (CanLII), paras. 13-16, 64-65). It is as if proposed expert evidence of mixed law and fact is equally eligible to reach the gate as any expert evidence of fact. Consequently, much expert evidence of mixed law and fact has been routinely admitted below in different areas of law.
3. R. v. Fisher, [1961] S.C.R. 535 remains the most recent decision by the Supreme Court on the issue: in excluding opinion evidence of mixed law and fact, the full and unanimous Court were “all in substantial agreement” with the reasons of the majority of a five-judge panel of Ontario Court of Appeal that “[w]here the opinion tendered, involves what is a mixed question of law and fact, the opinion is not admissible” (at p. 538).
4. Despite the above direct statement, jurisprudence below continues to contradict Fisher to purportedly follow Mohan's apparent generalization, but without citation, of the earlier decision of R. v. Graat, 1982 SCC 33 CanLII (which only dealt with opinion evidence from non-expert witnesses on a question of fact alone, namely, the lay observations of signs of drunkeness of a motorist) that "the rule which excluded expert evidence in respect of the ultimate issue ... is no longer of general application ..." [Mohan, p. 24] even where opinion evidence is on an ultimate issue of mixed law and fact. Mohan did not directly cite Fisher nor directly discuss expert evidence of mixed law and fact.
5. In Graat, the Supreme Court upheld the decision of the Ontario Court of Appeal, and admitted the lay opinion evidence while noting with apparent approval in obiter the unanimous Court of Appeal's note "that opinion evidence is properly rejected when it involves a legal component" [Graat, p. 825].
6. The nature of a question of mixed law and fact has been explained earlier: “questions of law are questions about what the correct legal test is; questions of fact are questions about what actually took place between the parties; and questions of mixed law and fact are questions about whether the facts satisfy the legal tests.” [Canada (Director of Investigation and Research, Competition Act) v. Southam Inc., [1997] 1 S.C.R. 748.] “Questions of mixed fact and law involve applying a legal standard to a set of facts … On the other hand, factual findings or inferences require making a conclusion of fact based on a set of facts.” [Housen v. Nikolaisen, 2002 SCC 33 (CanLII).]
7. In Mohan, the Court was addressing disputed opinion evidence on a question of fact, namely whether Dr. Mohan’s disposition fit a certain character profile. The Court, in effect, summarized the development in the jurisprudence on expert evidence on questions of fact, when it stated, obiter in respect of evidence of mixed law and fact, that there is no longer a general rule barring opinion evidence on the “ultimate issue”.
8. In Fisher, on the other hand, while dealing with evidence of certain capacity of an accused which was also a question of fact, this Court adopted the following explicit restriction against opinion of mixed law and fact from the Ontario Court of Appeal [R. v. Fisher, 1961 CanLII 38 (ONCA), paras. 52-53]:
[52] Where the opinion tendered, involves what is a mixed question of law and fact, the opinion is not admissible. Thus, a medical man may not be allowed in terms to give his opinion that an accused was a criminal sexual psychopath, for inherent in that status is a difficult legal concept […].
[53] […] The question of appellant’s capacity, of course, was for the jury, as was the question of his actual intent. These are questions of fact and not questions of mixed law and fact. […]
9. It is submitted that opinion evidence of mixed law and fact is inherently beyond the fact-finding process, involves a legal component, and is therefore beyond the proper scope of expert opinion evidence.
10. Fisher has been inadvertently overlooked in error and effectively overruled by the succinct but incomplete generalization by Mohan. Mohan, in hindsight, ought to have stated that "there is no longer a general rule barring opinion evidence on the ultimate issue of fact". The omission of the assumed factual nature of opinion evidence has unfortunately led to the current entrenched misapprehension of Mohan. The misapprehension might have been contributed to, in part, by difficulty in distinguishing ultimate questions of fact from ultimate questions of law on rare occasions, although there should not be any difficulty in Mohan and Graat as they clearly involved questions of fact alone. Ultimately, however, Fisher remains good law to exclude opinion evidence of mixed law and fact.
11. The current jurisprudence erroneously permits admission of opinion evidence of mixed law and fact in many areas of law including family, personal injury, land use and planning, and commercial law [a list of such cases is available in draft form on request by reader]. The flawed jurisprudence and consequently flawed expert evidence not only induce miscarriages of justice, they also implicate the Canadian constitutional order and the rule of law.
Inconsistency with the Constitutional Order and the Rule of Law
12. It is submitted that the admission of expert evidence on issues of mixed law and fact undermines the Canadian constitutional order and the rule of law in several ways.
13. First, the province of the jury is not usurped but is enlarged or distorted, as its attributes are expanded. Ordinarily, the jury must take legal instructions and guidance only from the judge. But with such expert evidence, the jury has an enlarged opportunity or power to hear and consider legal opinions from the expert. Indeed, it is more than just legal opinions, but legal decisions by the expert on how the law is applied to the facts, dressed as mere opinion evidence of an independent and impartial expert.
14. Second, the power of the expert is expanded. Their power exceeds the power of the judge in a trial in important aspects, including (a) while the expert can, the judge cannot tell the jury what outcomes on questions of mixed law and fact to select, or what the Court’s opinion or decision would be if the Court were to decide the legal dispute; (b) while the expert is practically exempt from providing written legal analysis on the underlying questions of law for appellate review, the judge must provide proportional and sufficient legal analysis; and (c) on appellate review, the expert enjoys greater deference than the judge because firstly, the expert’s legal opinion is paradoxically deemed an issue of fact; and secondly, any legal analysis of underlying questions of law are further insulated behind a tolerated absence[1] of expert analysis.
15. Third, the role of the judiciary is obscured and risks being usurped. In our constitutional order, it is the primary role of the judiciary to interpret and apply the law to the cases brought before it: British Columbia v. Imperial Tobacco Canada Ltd., 2005 SCC 49, paras. 50, 59. Saved for specific and properly delegated statutory powers to inferior tribunals, the judiciary has exclusive power and responsibility to decide the cases before it. The judiciary risks “an abdication of judicial responsibility”[2] if they were to consider or rely on the expert’s legal opinion or legal advice in discharging its constitutionally independent duty to decide the cases before the court.
16. Fourth, there is no legislative power for the judiciary to effectively institute, de facto, an inferior tribunal where experts are permitted to apply the law to the facts, and decide ultimate issues of mixed law and fact although subject to a full right of appeal de novo to the judge at the trial.
17. Fifth, the expert further infringes the jurisdiction of the legal profession by engaging in the unauthorized practice of law with immunity. The expert engages in the trade of legal opinions they happen to have without any accountability to any Law Society for the protection of the public. Even when experts have been caught at trial for flawed expert evidence, errors and omissions in their legal opinions, and certain other misconduct unbecoming of an expert, their disciplinary record of prior adverse judicial comments are scraped clean for their next performance before a fresh new jury.[3]
[1] For example, see Bruff-Murphy, 2017 ONCA 502 CanLII, para. 47; Pucci v. Wawanesa, 2020 ONCA 265 CanLII, para. 12.
[2] Saadati v. Moorhead, 2017 SCC 28 CanLII, para. 22.
[3] Bruff-Murphy, para. 32: prior adverse judicial comments are not a proper subject for cross-examination.
1. Over the past generation, while the rules at common law on admissibility of expert opinion evidence have generally become more rigorous, there remains a foundational question which has not received direct guidance by the Supreme Court of Canada, namely, “Does the proper scope of expert evidence extend beyond the fact-finding process and a question of fact to include (legal) opinions on a question of mixed law and fact?”
2. Currently, jurisprudence on expert evidence makes little distinction between opinion evidence on issues of fact and issues of mixed law and fact. The admission process generally is to direct nearly all proposed expert evidence to the Mohan – White Burgess gate and see what will pass, regardless of whether it is legal opinion evidence from a former judge to advise a sitting judge on what law and interpretation to apply to the facts of the case, written “in a form that would easily translate into reasons for judgment” (Walsh v. BDO Dunwoody LLP, 2013, BCSC 1463 (CanLII), paras. 13-16, 64-65). It is as if proposed expert evidence of mixed law and fact is equally eligible to reach the gate as any expert evidence of fact. Consequently, much expert evidence of mixed law and fact has been routinely admitted below in different areas of law.
3. R. v. Fisher, [1961] S.C.R. 535 remains the most recent decision by the Supreme Court on the issue: in excluding opinion evidence of mixed law and fact, the full and unanimous Court were “all in substantial agreement” with the reasons of the majority of a five-judge panel of Ontario Court of Appeal that “[w]here the opinion tendered, involves what is a mixed question of law and fact, the opinion is not admissible” (at p. 538).
4. Despite the above direct statement, jurisprudence below continues to contradict Fisher to purportedly follow Mohan's apparent generalization, but without citation, of the earlier decision of R. v. Graat, 1982 SCC 33 CanLII (which only dealt with opinion evidence from non-expert witnesses on a question of fact alone, namely, the lay observations of signs of drunkeness of a motorist) that "the rule which excluded expert evidence in respect of the ultimate issue ... is no longer of general application ..." [Mohan, p. 24] even where opinion evidence is on an ultimate issue of mixed law and fact. Mohan did not directly cite Fisher nor directly discuss expert evidence of mixed law and fact.
5. In Graat, the Supreme Court upheld the decision of the Ontario Court of Appeal, and admitted the lay opinion evidence while noting with apparent approval in obiter the unanimous Court of Appeal's note "that opinion evidence is properly rejected when it involves a legal component" [Graat, p. 825].
6. The nature of a question of mixed law and fact has been explained earlier: “questions of law are questions about what the correct legal test is; questions of fact are questions about what actually took place between the parties; and questions of mixed law and fact are questions about whether the facts satisfy the legal tests.” [Canada (Director of Investigation and Research, Competition Act) v. Southam Inc., [1997] 1 S.C.R. 748.] “Questions of mixed fact and law involve applying a legal standard to a set of facts … On the other hand, factual findings or inferences require making a conclusion of fact based on a set of facts.” [Housen v. Nikolaisen, 2002 SCC 33 (CanLII).]
7. In Mohan, the Court was addressing disputed opinion evidence on a question of fact, namely whether Dr. Mohan’s disposition fit a certain character profile. The Court, in effect, summarized the development in the jurisprudence on expert evidence on questions of fact, when it stated, obiter in respect of evidence of mixed law and fact, that there is no longer a general rule barring opinion evidence on the “ultimate issue”.
8. In Fisher, on the other hand, while dealing with evidence of certain capacity of an accused which was also a question of fact, this Court adopted the following explicit restriction against opinion of mixed law and fact from the Ontario Court of Appeal [R. v. Fisher, 1961 CanLII 38 (ONCA), paras. 52-53]:
[52] Where the opinion tendered, involves what is a mixed question of law and fact, the opinion is not admissible. Thus, a medical man may not be allowed in terms to give his opinion that an accused was a criminal sexual psychopath, for inherent in that status is a difficult legal concept […].
[53] […] The question of appellant’s capacity, of course, was for the jury, as was the question of his actual intent. These are questions of fact and not questions of mixed law and fact. […]
9. It is submitted that opinion evidence of mixed law and fact is inherently beyond the fact-finding process, involves a legal component, and is therefore beyond the proper scope of expert opinion evidence.
10. Fisher has been inadvertently overlooked in error and effectively overruled by the succinct but incomplete generalization by Mohan. Mohan, in hindsight, ought to have stated that "there is no longer a general rule barring opinion evidence on the ultimate issue of fact". The omission of the assumed factual nature of opinion evidence has unfortunately led to the current entrenched misapprehension of Mohan. The misapprehension might have been contributed to, in part, by difficulty in distinguishing ultimate questions of fact from ultimate questions of law on rare occasions, although there should not be any difficulty in Mohan and Graat as they clearly involved questions of fact alone. Ultimately, however, Fisher remains good law to exclude opinion evidence of mixed law and fact.
11. The current jurisprudence erroneously permits admission of opinion evidence of mixed law and fact in many areas of law including family, personal injury, land use and planning, and commercial law [a list of such cases is available in draft form on request by reader]. The flawed jurisprudence and consequently flawed expert evidence not only induce miscarriages of justice, they also implicate the Canadian constitutional order and the rule of law.
Inconsistency with the Constitutional Order and the Rule of Law
12. It is submitted that the admission of expert evidence on issues of mixed law and fact undermines the Canadian constitutional order and the rule of law in several ways.
13. First, the province of the jury is not usurped but is enlarged or distorted, as its attributes are expanded. Ordinarily, the jury must take legal instructions and guidance only from the judge. But with such expert evidence, the jury has an enlarged opportunity or power to hear and consider legal opinions from the expert. Indeed, it is more than just legal opinions, but legal decisions by the expert on how the law is applied to the facts, dressed as mere opinion evidence of an independent and impartial expert.
14. Second, the power of the expert is expanded. Their power exceeds the power of the judge in a trial in important aspects, including (a) while the expert can, the judge cannot tell the jury what outcomes on questions of mixed law and fact to select, or what the Court’s opinion or decision would be if the Court were to decide the legal dispute; (b) while the expert is practically exempt from providing written legal analysis on the underlying questions of law for appellate review, the judge must provide proportional and sufficient legal analysis; and (c) on appellate review, the expert enjoys greater deference than the judge because firstly, the expert’s legal opinion is paradoxically deemed an issue of fact; and secondly, any legal analysis of underlying questions of law are further insulated behind a tolerated absence[1] of expert analysis.
15. Third, the role of the judiciary is obscured and risks being usurped. In our constitutional order, it is the primary role of the judiciary to interpret and apply the law to the cases brought before it: British Columbia v. Imperial Tobacco Canada Ltd., 2005 SCC 49, paras. 50, 59. Saved for specific and properly delegated statutory powers to inferior tribunals, the judiciary has exclusive power and responsibility to decide the cases before it. The judiciary risks “an abdication of judicial responsibility”[2] if they were to consider or rely on the expert’s legal opinion or legal advice in discharging its constitutionally independent duty to decide the cases before the court.
16. Fourth, there is no legislative power for the judiciary to effectively institute, de facto, an inferior tribunal where experts are permitted to apply the law to the facts, and decide ultimate issues of mixed law and fact although subject to a full right of appeal de novo to the judge at the trial.
17. Fifth, the expert further infringes the jurisdiction of the legal profession by engaging in the unauthorized practice of law with immunity. The expert engages in the trade of legal opinions they happen to have without any accountability to any Law Society for the protection of the public. Even when experts have been caught at trial for flawed expert evidence, errors and omissions in their legal opinions, and certain other misconduct unbecoming of an expert, their disciplinary record of prior adverse judicial comments are scraped clean for their next performance before a fresh new jury.[3]
[1] For example, see Bruff-Murphy, 2017 ONCA 502 CanLII, para. 47; Pucci v. Wawanesa, 2020 ONCA 265 CanLII, para. 12.
[2] Saadati v. Moorhead, 2017 SCC 28 CanLII, para. 22.
[3] Bruff-Murphy, para. 32: prior adverse judicial comments are not a proper subject for cross-examination.