Expert Evidence and Testimony

By David Debenham

“If only you could see what I have seen with your eyes” (Blade Runner, 1982)

The role of the optometrist is to prescribe spectacles or contact lenses.  It is to assist the patient in seeing the world more clearly.  So too, expert witnesses should bring their skillset to bear to help a judge to better evaluate the evidence they are seeing.  Too often experts behave like the over-anxious, over-achieving student who shouts out the answer to the class rather than simply explains the steps to be taken by the class to get to the right answer. The expert’s role is to educate the judge by using technical expertise that the court is not privy to, not to supersede the judge or jury as decision maker. 

In Logix Data Products v. The Queen[1] the taxpayer claimed a Scientific Research and Experimental Development tax credit (a “SRED”) in relation to a solar panel it developed to replace shingles on a roof. CRA alleged that the panel did not advance the science by conducting scientific research, and therefore did not qualify for the credit.  The court disallowed the expert’s report on several grounds: (1) it purported to give an opinion on the ultimate issue before the court, being, whether the work done by the taxpayer constituted scientific research for the purposes of the Income Tax Act, rather than merely assisting the court in making that determination, (2) the expert report contains several opinions without setting out the facts and assumptions upon which those opinions are based, (3) the report does not set out the professional literature that supports the basis of his opinion, and was reviewed prior to giving his opinion(4) the report voices the opinion that the taxpayer’s claim meets the requirements of SRED was not an independent evaluation but was one sided advocacy, (5) giving an opinion of the proper interpretation of domestic law is inadmissible, as this is the purview of the judge.  The court noted:

“ An expert opinion may assist the court in evaluating technical evidence…. But, at the end of the day, the expert’s role is limited to providing the court with a set of prescription glasses through which the technical information may be viewed before being analyzed and weighed by the trial judge. Undoubtedly, each opposing expert witness will attempt to ensure that its focal specifications are adopted by the court. However, it is the prerogative of the trial judge to prefer one prescription over another.[2] 


[1] [2021] TCC 36

[2] Citing RIS-Christie Ltd. v. The Queen 1998 CanLII 8876 (FCA), [1998] F.C.J. No 1890, [1999] 1 CTC 132 (FCA) [RIS-Christie], at para. 12.

Published by

David Debenham

David Debenham

David, CPA, CMA, is the co-chair of the Fraud Law Group of the law firm of McMillan LLP