Preparing the Expert Witness

• Author: Justice Cameron Gunn/Mona Duckett/Patrick McGuinty
• Pages: 83-98

83

Preparing the

Expert Witness

5

I. Understanding the Witness’s Evidence and Pinpointing

Their Qualications ....................................... 

II. The Expert’s Duty to Be Impartial, Unbiased, and Independent . . . . 

III. Discussing the Issue of Language with the Expert Witness ........ 

IV. Five Means Five: The Canada Evidence Act Limitations .......... 

V. Providing Proper Notice in the Context of Expert Evidence ........ 

VI. Preparing to Cross-Examine the Expert Witness ................. 

A. Information Gathering ............................... 

B. Analysis ........................................... 

C. Organization ....................................... 

Copyright © 2023 Emond Montgomery Publications. All Rights Reserved.

84Part I Witness Preparation

This chapter focuses on the steps that counsel should take in preparing to adduce

expert evidence at trial. It should be read in conjunction with Chapter 11, Presenting

Expert Opinion Evidence.

Expert opinion evidence haunts the criminal law. In some cases, flawed expert

opinion evidence has contributed to wrongful convictions. Trial counsel have an ethi-

cal obligation to ensure that expert opinion evidence stays within its proper boundar-

ies. This starts in pre-trial preparation. The section headings below identify specific

tasks to focus on when preparing to adduce the evidence of an expert witness. Each

section oers practical tips to assist in presenting expert witness evidence in an ethi-

cal and ecient manner.1

I. Understanding the Witness’s Evidence

and Pinpointing Their Qualifications

Prior to trial, familiarize yourself with the evidence your expert will give. Read their

report and make notes of topics that you have diculty understanding. If you have

diculty understanding portions of their report, chances are the trier of fact will

have diculty understanding the expert’s viva voce evidence on the topic. You should

research topics that your expert will cover simply to familiarize yourself with them.

Arrange to meet with your expert well in advance of trial. Ask them clarifying

questions to ensure that you understand their evidence. It is crucial that you under-

stand the opinion that the expert will be conveying to the trier of fact. If you don’t

fully understand their evidence, you risk allowing the expert witness to stray into

forbidden territory and testify to matters that fall outside their expertise. To that end,

equally important to understanding the witness’s evidence is your obligation to pin-

point their expertise and the areas in which they should be qualified to give opinion

evidence. This is something to discuss with the expert witness. Although the issue of

qualification is a legal issue for the trial judge to decide, you should determine before-

hand whether the expert is comfortable being qualified in a particular field and able to

give expert opinion evidence on a subject matter within that field. Advise your expert

that they must be open and candid with you in discussing the legitimate bounds of

their expertise. This is an ethical obligation.2 An expert should be able to discuss with

you the limits of their expertise. The expert should be told that if a lawyer at trial asks

them a question outside their area of expertise, they should decline to answer and

explain why. That is the expert’s obligation. Several dangers arise when an expert

strays outside their qualifications.3

1 For a broader examination of the law regarding expert opinion evidence, see M Gourlay et al,

Modern Criminal Evidence (Toronto: Emond, 2022) ch 4, s IV, “Expert Opinion.”

2 See the Supreme Court of Canada’s comments in R v Sekhon, 2014 SCC 15 at paras 46-47.

3 See the Supreme Court of Canada’s comments in R v Sekhon, 2014 SCC 15 at paras 46-47.

Copyright © 2023 Emond Montgomery Publications. All Rights Reserved.