In Anderson v Anderson, 2024 ONSC 5891 (“Anderson”) a Will Challenge, the court addressed the law surrounding the admissibility of expert opinion evidence using the test established in R. v. Mohan, 1994 80 SCC (“Mohan”).

Brief Background

The Applicant sought an order of the Court to validate her mother’s (the “Deceased”) “valid and lawful holograph Will”, executed on January 5, 2016 (the “Holograph Will”).[1] Meanwhile, the Respondents, who were the remaining children of the Deceased, asserted that the Will the Deceased prepared in 2012 was her only valid Will on the basis that the Deceased did not have testamentary capacity to make a Holograph Will. The Respondents sought the opinion of a geriatric professional, Dr. Hermann, in assessing the Deceased’s testamentary capacity at the time the Holograph Will was made. The court asserted that Dr. Hermann’s report was admitted based on Mohan.

Overview of the Mohan Test

The test to determine the admission of expert opinion evidence is outlined in Mohan, and expanded upon in the 2015 decision White Burgess Langille Inman v. Abbott and Haliburton Co, 2015 SCC 23.[2]

The Mohan test is comprised of two steps (the “Mohan Test”). The first step, involves a determination of whether the evidence passes the threshold requirements of admissibility, which requires consideration of the following four factors:

1. Relevance;
2. Necessity;
3. Absence of an exclusionary rule; and
4. A properly qualified expert.[3]

These factors will be discussed at greater length within. The second step, which is described as the “discretionary gatekeeping step”, requires the trial judge to establish whether the benefits stemming from the admission of the expert evidence outweigh the potential harms that may result from its admission into the trial process.[4]

The Issues

Dr. Hermann was asked to answer the following two questions:[5]

1. Did the Deceased have a sound and disposing mind?
2. Were suspicious circumstances present at the time the Deceased purportedly executed the holograph Will?

Dr. Hermann found that there was a “significant risk” that the Deceased did not have sufficient testamentary capacity to execute the Holograph Will.[6]  This conclusion was reached by Mr. Hermann’s review of the Deceased’s medical records, her retirement home’s records, and her insurance records. In addition, Dr. Hermann reviewed the documents pertaining to the litigation.

Dr. Hermann found that prior to the Deceased’s purported execution of the Holograph Will, the Deceased was highly susceptible to undue influence due to the decline in her cognitive ability and behavioural impairment.

Following these results, the Applicant asserted that Dr. Hermann’s report was not admissible on the following basis:

1. The test of relevance was not met and/or satisfied;
2. The necessity and qualification requirements set out in the Mohan test were not met; and
3. The cost benefit analysis found within the second step of the Mohan test was not met.

The Applicant’s contention was that Dr. Hermann’s report was not necessary to assist the court because it merely summarized the Deceased’s existing records. Additionally, in the Applicant’s words, the Deceased’s records were in “plain English” and therefore did not require a capacity assessors review.

The Court did not side with the Applicant, rather it stated Dr. Hermann’s report met the guidelines found in R. v. Abbey, 1982 25. The Court asserted that an expert’s opinion can be vital to a decision because it provides a judge with details and scientific background that will often be outside of the experience and knowledge of such judge.[7] Additionally, citing R. v. Turner, 1974 1825, the Court importantly stated that expert witnesses will often base their judgement on second-hand evidence. Moreover, the most important job of an expert witness is not to provide the Court with a testimony based on firsthand evidence, but rather to provide an opinion.

The court reinforced its analysis based on the following excerpt provided from Wilband v. R, 1996 3:

[18] The value of a psychiatrist’s opinion may be affected to the extent to which it may rest on second-hand source material; but that goes to the weight and not to the receivability in evidence of the opinion, which opinion is no evidence of the truth of the information, but evidence of the opinion formed on the basis of that information.

The court found that Dr. Hermann provided the court with important information regarding medical concepts allowing the court to make an informed decision of the issue at hand.

The Applicant also stated that Dr. Hermann’s findings were contrary to the findings of the Deceased’s capacity prior to her execution of the holograph Will. For this reason, the Applicant asserted that Dr. Hermann was bias and impartial. The Court rejected this argument on the basis that there was insufficient evidence provided to demonstrate Dr. Hermann’s alleged bias. In the Court’s analysis it noted the decision of White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 SCC 23 (CanLII):

[36] It is well established that an expert’s opinion must be independent, impartial and objective, and given with a view to providing assistance to the decision maker … However, these factors generally have an impact on the probative value of the expert’s opinion and are not always insurmountable barriers to the admissibility of his or her testimony. Nor do they necessarily “disqualify” the expert. For expert testimony to be inadmissible, more than a simple appearance of bias is necessary. The question is not whether a reasonable person would consider that the expert is not independent. Rather, what must be determined is whether the expert’s lack of independence renders him or her incapable of giving an impartial opinion in the specific circumstances of the case.

Part Two of the Mohan Test:

The second step of the Mohan test requires a court to balance the cost of the expert against the value/benefits of the expert, otherwise regarded as a cost benefit analysis. In Anderson, the court stated that the benefits of the Dr. Hermann’s report were worth the additional costs to the application. The Court asserted that the cost of the report was not substantial, it will not take up significant time, and that the findings of Dr. Hermann had “probative value” which outweighed any “prejudicial impact”. [8]

Concluding Comments

Anderson provides further insight into how a court will treat expert’s reports based on the Supreme Court of Canada criteria and in weighing such factors against the legal position taken by litigating parties. In Will challenge proceedings it is often critical to tender expert evidence where testamentary incapacity is alleged. Though there continue to be interim motions and trial wranglings over admissibility, it has long since been established that medical expert opinion is of great assistance to the court in such matters.

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[1] Anderson v. Anderson, 2024 ONSC 5891

[2] White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 SCC 23 (CanLII), [2015] 2 SCR 182

[3] Ibid

[4] Ibid

[5] Ibid at para 4.

[6] Ibid at para 9.

[7] Ibid at para 44

[8] Ibid at para 30.