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Expert Evidence: Fact vs. Opinion

Written by admin on . Posted in Civil Procedure.

When advancing a personal injury lawsuit in British Columbia expert evidence plays a key role.  Be it the diagnosis of injury, prognosis, future care needs, disability or other topics there are no shortage of areas that call for the assistance of expert evidence.
When preparing for trial notice of expert opinion evidence has to be given in compliance with Rule 40A (after July 1, Rule 40A will be replaced with the new Rule 11).
Just because a professional such as a doctor is giving evidence does not necessarily mean that the Rule regarding expert opinion evidence is triggered.  If an expert is giving purely factual evidence then Rule 40A does not apply.  However, if the evidence is not purely factual but also contains opinion then the notice period in Rule 40A is likely triggered.  So what exactly is an expert opinion?  Last week reasons for judgement were released discussing this distinction.
In last week’s case (Anderson v. Dwyer) the Court was asked whether a chiropractor interpreting an X-ray was factual evidence or opinion evidence.  Mr. Justice Schultes provided the following very useful analysis:

[13] In determining the admissibility of Dr. Wooden’s evidence, it is crucial to bear in mind the distinction between expert opinion and factual evidence that is given by potential expert witnesses.  As the learned author of Phippson on Evidence (16th ed.) helpfully observes at para. 33-10, p. 972:

There is an important if elusive distinction to be made in the categorization of expert evidence.  It is generally accepted that there is a difference between evidence of fact and evidence of opinion notwithstanding that it may be difficult to identify the line which divides the two.  It is also well understood that in practice a witness of fact may not be able entirely to disentangle his perceptions from the inferences he has drawn from them.  Although the courts often talk of “expert evidence” as if it were a single category representing in every case an exception to the rule against the reception of opinion evidence, it is suggested that a similar distinction exists in the evidence of experts and it is one which has considerable relevance both to the procedural aspects and to the assessment of the weight of expert evidence.  Expert witnesses have the advantage of a particular skill or training.  This not only enables them to form opinions and to draw inferences from observed facts but also to identify facts which may be obscure or invisible to the law witness.  The latter might simply be described as scientific evidence; the former as expert evidence of opinion.  A microbiologist who looks through a microscope and identifies a microbe is perceiving a fact, no less than the bank clerk who sees an armed robbery committed.  The only difference is that the former can use a particular instrument and can ascribe objective significance to the data he perceives.  The question of subjective assessment and interpretation which is the essence of opinion evidence hardly enters into the matter at all.  An example of the dichotomy can be seen in the case of a conflict between experts on handwriting as to the authenticity of a document.  By virtue of their training, such experts would be able to distinguish parts of letters or techniques of word formation which a layman would be unable to observe.  This is the scientific part of their work.  The question of which features are significant and the inferences to be drawn from them are questions of judgment, assessment, opinion.  This distinction which has now been accorded a measure of judicial recognition is thought to be of some practical utility in considering the weight of evidence given by experts both taken in isolation and when assessing the merits of two competing theories.

[14] This distinction is a very meaningful one in this case.  Any evidence by Dr. Wooden seeking to offer an opinion about the plaintiff’s injuries, such as the inferences to be drawn from the observations in the x-rays or with respect to the cause or mechanism of the injury, would be prohibited because of the plaintiff’s failure to comply with Rule 40A.  However, the witness’s factual narrative of the actions he took and the observations he made, including describing without interpretation, the anatomical features he observed in the x-rays does not amount to offering an opinion and does not offend the Rule.  The fact that he brings special training or experience to bear in having taken those actions and made those observations is not determinative.  It is whether he draws inferences or offers opinion beyond what the actual evidence itself is capable of revealing.

[15] In this regard, I consider this kind of factual evidence to be analogous to those matters described by Madam Justice Garson as being “more in the nature of observations” as opposed to inferences having complex interpretive or diagnostic components when she described how their inclusion in records sought to be admitted as business records did not offend Rule 40A in Egli v. Egli, 2003 BCSC 1716 at para. 25 which was relied on by the defendant in submissions.

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