Admissibility of Expert Evidence – SCC Decisions “Abbey” & “Lavallee” Part 1


A discussion on R. v. Abbey, 1982 CanLII 25 (SCC) and R. v. Lavallee, 1990 CanLII 95 (SCC)

The process of preparing and building your evidence for trial begins in early stages of litigation. Let’s discuss some basics:


The facts of your case should be well known to you. To assist you with this, ask yourself 4 questions:

  1. What is the Plaintiff claiming in this action?
  2. What facts must you prove?
  3. What evidence do you need to prove the Plaintiff’s case? and
  4. What risk factors exist?

Whether you are acting on behalf of the Plaintiff, or assisting the defence, these questions are a good start for you to consider.

As you manage your files, it is important to carefully review your documents, such as: your ambulance crew report, hospital records, clinical records, radiology reports, expert reports, witness statements, etc: Your purpose is to identify any inconsistencies or inaccuracies that may exist.

We review a BCSC decision in which material facts were deemed to be inaccurate. These material facts were relied on by the Plaintiff’s experts.  The following risks may result:

1. The weight of your expert’s opinion may be dismissed or diminished, and

2. The value of your client’s case may be impacted.

Tambosso v. Holmes, 2015 BCSC 359 (CanLii) (Update:  Decision successfully appealed: Tambosso v. Holmes, 2016 BCCA 373 (CanLII) (See next post  re: appeal decision)

The Judge scrutinized the Client’s subjective evidence provided to the ambulance crew and hospital physicians compared with the Client’s subjective evidence provided to the experts in this litigation, and there was a marked difference in these complaints. Firstly, there was no report of “striking her head” in the initial reports. Nor was there any mention of any “trauma” or “fear” that was experienced during this incident. However, this Client advised the IME experts that she observed the “Defendant’s eyes as he accelerated his vehicle towards her while she stood on the highway” creating intense fear that she was going to die. These facts were material as they were stated to be the “triggering event” that caused her PTSD, which was being claimed in this action. The major issue in this case was that the client described facts of circumstance of the collision which were deemed false.

The legal principles that are often raised at trial when the opinion of an expert is being challenged based on reliance of inaccurate facts are outlined in two leading authority from the Supreme Court of Canada. They are R. v. Abbey, 1982 CanLii 25 (SCC) and R. v. Lavallee, 1990 CanLii 95 (SCC). These cases are pursuant to the Criminal Code of Canada the 1st dealing with an insanity pleas, and the 2nd dealing with battered woman syndrome respectively.

These two cases were raised and discussed in Tambosso:

The principles are noted:

In R. v. Abbey, 1982 CanLII 25 (SCC) “establishes that facts relied on or assumed by an expert for the purpose of forming an opinion must be proven in evidence before the expert opinion can be given any weight. In other words, the lack of a factual foundation will cause the expert’s opinion to be given little, if any weight.”

The approach outlined in Abbey was endorsed by the SCC R. v. Lavallee, 1990 CanLII 95 (SCC): “while each of the specific facts underlying the expert’s opinion need not be proven in evidence, there must be some admissible evidence to establish the foundation of the expert’s opinion. The more the expert relies on facts not proved in evidence, the less weight is to be given to the opinion.”

In applying these principles in Tambosso, the Court found that as the facts were deemed to be unproven in evidence, the weight of the experts’ reports were diminished, which in effect, impacted the final decision in this case. The Judge states “the opinions are not of assistance to the Court.” 

The Court stated the following:

Credibility of Ms. Tambosso

“In the opening of these reasons, I referred to the defence position that the major issue in this case is the credibility, or lack thereof, of the plaintiff. I have already found in these reasons that the event which the plaintiff alleges is the triggering event of her alleged PTSD and other psychological concerns was the incident following the 2008 accident, ie. when the plaintiff ran down the hill towards the defendant Holmes and made eye contact with him, did not occur. The evidence of the plaintiff with regards to that incident was only the beginning of her attempts to fabricate evidence so as to exaggerate what had occurred, her injuries and their effect on her life since 2008.”

The Court further stated that “the submissions of the plaintiff, however, were not particularly helpful in that the emphasis was on the alleged PTSD and mild traumatic brain injury issues which I find were not proven.” The award for non-pecuniary damages was $25,000.

This decision has been successfully appealed.  See Next Post.

Appeal:  Tambosso v. Holmes, 2016 BCCA 373 (CanLII)

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