R. v. Mohan: A Precedent in Admitting Expert Witness Evidence

In matrimonial and shareholder disputes, a Chartered Business Valuator (“CBV”) may be called to testify as an expert witness. In cases where both sides have hired their own CBV to opine on fair market value or other quantifications, both CBVs may testify. First, in order for expert evidence to be admitted, the CBV’s evidence must meet a series of criteria.

R. v. Mohan set a precedent by indicating that expert evidence should be excluded if it does not pass the following tests:

1. Relevance;
2. Necessity in assisting the trier of fact;
3. The absence of any exclusionary rule; and
4. A properly qualified expert.

This blog explores what these criteria mean and how they apply to reports issued by CBVs.

1) Relevance

Logical relevance is a threshold requirement for expert evidence. Evidence must be logically relevant to the matter at hand, and whether or not evidence is relevant is a question of law, to be decided by a judge.

For example, in a family law matter where a business forms a portion of net family property, a valuation of that business and the related contingent tax report at the correct date may be relevant for quantifying net family property. Likewise, when determining the quantum of child support, an income for support report prepared in accordance with the Federal Child Support Guidelines may be relevant.

Even if evidence is logically relevant, however, it still may not be admissible if the negative impact on the trial process outweighs the benefits. For example, additional questions set out in Mohan include:

• Does the prejudicial effect of the evidence on the jurors outweigh the evidences probative value?
• Is the evidences effect on the jury out of proportion with its level of reliability?
• Does the evidence require an inordinate amount of time?
• Is the evidence too difficult to understand?

For example, an expert report that is too complicated to understand, may remain inadmissible, even though it is relevant.

2) Necessity in Assisting the Trier of Fact

Legal matters often require expertise that is outside of the knowledge or experience of the trier of fact. Expert witness evidence can help the trier of fact understand these technical matters at issue. If the trier of fact could form their conclusions without the assistance of an expert, then the evidence may not be necessary.

Determining business values and quantifying income and losses is a matter that requires education, training, and experience to develop proficiency. This is typically outside of the expertise of the trier of fact, and therefore the assistance of an expert may be necessary.

3) The Absence of Any Exclusionary Rules

Even in situations when expert evidence is relevant and necessary, it may still be excluded if it is prohibited by an exclusionary rule. Some examples include evidence that relies on hearsay, or evidence that was obtained in a manner that infringed or denied rights and freedoms guaranteed by The Canadian Charter of Rights and Freedoms.

Although this criterion does not often arise in the context of CBVs, it could arise in an example where the CBV relies on hearsay when preparing their expert reports. In this circumstance, the reports may not meet the criteria of Mohan.

4) A Properly Qualified Expert

Finally, the expert witness must show that they have acquired special knowledge through study or experience in respect to the matters on which they are testifying. Expert witnesses should not testify to matters considered outside of their areas of expertise.

For example, although an expert may be qualified to speak to business valuation matters, that does not necessarily mean that they are qualified to speak matters regarding income available for support purposes.

In Closing

R. v. Mohan, a case from 1994, continues to be the precedent for excluding expert witness evidence in 2020. For that reason, the criteria discussed continues to be important working knowledge for everyone involved in the litigation process.

If you would like to discuss your unique situation, give the experts at Davis Martindale a call. We would be happy to have a personalized discussion with you.