Opinion Evidence

• Author: Matthew Gourlay/Brock Jones/Jill D. Makepeace/Glen Crisp/Renee Pomerance
• Pages: 81-150

CHAPTER 4

OPINION EVIDENCE

I. Introduction ...................................................... 

II. Fact Versus Opinion................................................ 

A. Experimental Evidence .......................................... 

B. Conclusions Drawn from Financial Records ........................ 

C. Evidence from a Treating Medical Professional...................... 

D. Voice Identification ............................................. 

E. Evidence Regarding Non-Controversial Technology................. 

III. Lay Opinion Evidence .............................................. 

A. Principles of Admissibility ........................................ 

B. Checklist...................................................... 

IV. Expert Opinion .................................................... 

A. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

B. Rules and Principles of Admissibility ............................... 

. The Admissibility Framework .................................. 

(A) First Stage: Threshold Inquiry .............................. 

(B) Second Stage: A Cost – Benefit Analysis .................... 

. The Ultimate Issue .......................................... 

. The Defence Expert ......................................... 

. The Number of Experts...................................... 

. The Role of Precedent ...................................... 

. Statutory Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

C. Pre-Trial Considerations ......................................... 

. Retaining the Expert ........................................ 

. Consulting with the Expert ................................... 

. Notice (Code Section .) ................................. 

(A) Remedies .............................................. 

. Disclosure ................................................. 

(A) Material Relied on by the Expert........................... 

(B) Communication Between Counsel and Expert .............. 

(C) Draft Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

(D) Disclosure of Hypotheticals .............................. 

(E) Disclosure of Material in Crown’s Possession in Anticipation

ofCross-Examination.................................... 

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(F) Defence Disclosure...................................... 

. Testing of Exhibits .......................................... 

D. The Expert Report ............................................. 

E. Presenting Expert Opinion Evidence ............................. 

. Use of Slide Presentations and Testimonial Aids................. 

. Where an Opinion Exceeds the Scope of Expertise—Trial Remedy ... 

. Use of Hypotheticals ........................................ 

F. Challenging the Expert Witness.................................. 

. Case-Specific Information ................................... 

. Cross-Examination on Other Authorities....................... 

. Reference to Prior Judicial Findings ........................... 

G. Reply Evidence................................................ 

H. Closing Address ............................................... 

I. Instructing the Jury ............................................ 

J. Issues on Appeal .............................................. 

. Standard of Review—Admissibility............................. 

. Where an Opinion Exceeds the Scope of Expertise—Minor

Breaches .................................................. 

. Fresh Expert Opinion Evidence ............................... 

K. Expert Opinion Evidence in Other Contexts: Bail and Sentencing..... 

L. Checklist/Summary............................................ 

Appendix A: Template—Basic Instruction Letter........................... 

I. INTRODUCTION

An opinion is a conclusion or inference drawn from an observed fact.1 Testimony that

engages opinion is generally not permitted to be tendered by a witness and is pre-

sumptively inadmissible because it is for the trier of fact to come to conclusions and

make inferences based on the evidence, n ot the witness.2 An ill-considered or irrelevant

opinion from the mouth of a witness may act unfairly against one side, distorting, and

in some cases undermining, the entire fact-finding process.3 We therefore expect wit-

nesses to limit their evidence to action s taken or perceptions made in a given case.4

However, there is often a need for a witness to provide their o pinion in order to bet-

ter describe the unfolding narrative or to assi st the trier of fact in making sense of other

evidence tendered in a case. In appre ciation of the need to resort to such evidence, two

principled common law exceptions add ressing lay opinion and expert opinion evid ence

have developed, allowing a part y to rely on opinion upon establishing its admissibility

1 Rv Leclerc, 2001 CanLI I 16729 at 37 (Qc CQ), referencing Rv Abbey, [1982] 2 SCR 24 at 42 [Abbey 1982].

2 Abbey 1982, ibid; Rv K, A, 1999 CanLII 3793 at par as 71, 73 (Ont CA); Rv Sandoval-Barillas, 2017 ABCA 154

at para 55, referenc ing Rv Wiens, 2016 BCCA 34, leave to app eal to SCC refused, [2016] SCCA No 189.

3 White Burgess Langille I nman v Abbott and Halibu rton Co, 2015 SCC 23at para 14 [White Burgess], refer-

encing Graat v The Queen,[19 82] 2 SCR 819 at 836; Rv Abbey, 2009 ONCA 624 at par a 71 [Abbey 2009],

leave to appeal to SCC refu sed, [2010] SCCA No 125; Hal sbury’s Laws of Ca nada, Evidence(Markham, Ont:

LexisNexis Can ada, 2014 reissue) at HEV-137 “Ge neral rules Against O pinion Evidence.”

4 White Burgess, ibid at para 14; Rv Gavin, 2018 PECA 6 at para 46; Leclerc, supra note 1 at 37.

82MODERN CRIMINAL EVIDENCE

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on a balance of probabilities.5 The considerations that must be taken into account in

assessing the admissibil ity of this evidence will be examined in this chapter, along with

the practical implications that accompany its use.

II. FACT VERSUS OPINION

The first issue that must b e resolved for any counsel or judge contemplating the introduc-

tion of opinion evidence is to ensure that the ev idence in question is properly classified as

opinion. The opinion rule does not restrict any witness, including an expert, from being

able to testify to first-hand observations .6 Distinguishing between observations and opinion

can sometimes be difficult , however. There are not many witnesses who a re able to avoid

engaging in some sort of infe rence-making when describing what they have observed or

experienced in a given case.7 Non etheless, the case law reveals multiple examples where

attempts have been made to draw clear line s of demarcation. Five common categories of

evidence that illustrate these effor ts are examined in further detail below.

A. EXPERIMENTAL EVIDENCE

Simple experimental evidence, such as evidence relating to the time it takes to drive a

certain distance, is gene rally not considered to be opinion evidence at all and is there-

fore subject only to the well-establishe d evidentiary principles of relevance and materi-

ality (subject to judicial discretion to exclude).8 Distinguishing between fact and opinion

becomes more difficult, however, when consid ering certain types of experimental evi-

dence that go beyond the mundane.

In Collins,9 the accused was convicted of causing death by criminal negligence. The

Crown alleged that the victim was shot a s a result of the accused firing his rifle into a lake

at such an angle that the bullets ricocheted off th e surface of the water and hit the young

victim. An experiment was conducted demonstrating how this could have occurred.

The experiment was vide otaped and the evidence was tendered by the Crown through

the officer who conducted the experiment. The judge found that the officer had the

expertise to carry out the experiment, but restricted the officer’s testimony regarding

the experiment itself to the fac ts. It was not tendered as lay opinion evidence, nor was it

relied on as expert opini on evidence.

On appeal, it was argued that this evidence should have been considered to be

not only expert opinion evidence but novel scientific expert opinion evidence.10 The

5 Abbey 2009, supra note 3 at para 71; Leclerc, ibid; Sandoval-Barillas, supra note 2 at para 55, referencing

Wiens, supra note 2; Rv Vassel, 2018 ONCA 721 at paras 85-86.

6 Rv Sheriffe, 2015 ONC A 880 at para 106, referencing Ab bey 1982, supra note 1 at 42, leave to appeal

denied, 2016 CanL II 82916 (SCC); Rv K, A, supra note 2 at para 72.

7 Consider, for example, the te stimony of a witness who test ifies to the quality of merch andise (“the watch

looked expensi ve”) or the temperament of an in dividual observed dur ing the commission of an offen ce

(“he was extre mely angry”). This t ype of overlap is addre ssed in further detai l in Section III, “Lay O pinion.”

8 Rv Schertzer, 2015 ONCA 259 at para s 61-65; Rv Fattah, 2007 ABCA 400 at pa ras 16-18, leave to appeal

to SCC refused, 2008 C anLII 46996 (SCC). See Chapte r 1, Section V for furth er insight into legal relev ance

and ma teriali ty.

9 Rv Collins, 2001 CanLII 24124 (Ont CA).

10For more on what cons titutes novel science, see Se ction IV.B.1.(A)v.

Chapter 4 Opinion Evidence 83

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