Expert Evidence

• Author: Brian H. Greenspan/Vincenzo Rondinelli/Daniel Brown/Jill Witkin
• Pages: 273-298

273

Expert Evidence

9

I. Overview ................................................ 274

II. Expert Evidence: General Rules .............................. 274

A. Introduction ........................................ 274

B. The Test for Admissibility.............................. 275

C. Subject Matter of the Expertise ......................... 278

D. Notice Requirements ................................. 279

E. Examination of Experts at Trial ......................... 280

F. The Goudge Inquiry .................................. 283

III. Crown Expert Evidence in Sexual Assault Cases ................. 284

A. Introduction ........................................ 284

B. Capacity to Consent .................................. 285

C. Incremental and Delayed Disclosure .................... 286

D. Behavioural Characteristics of Abused Children ............ 286

E. Child Sexual Abuse Accommodation Syndrome ........... 287

F. Victim’s Neurological and Behavioural Response

to Trauma.......................................... 287

IV. Defence Expert Evidence in Sexual Assault Cases................ 291

A. Introduction ........................................ 291

B. Memory ........................................... 292

C. DNA .............................................. 293

D. Distinctive Behavioural Characteristics ................... 294

E. Toxicology.......................................... 295

F. Not Criminally Responsible on Account of Mental Disorder

and Automatism .................................... 296

© 2024 Emond Montgomery Publications. All Rights Reserved.

274 Prosecuting and Defending Sexual Oence Cases

I. Overview

Expert evidence can be highly valuable to both the Crown and the defence in a sexual

assault trial. Bodily fluids examined by an expert can assist the judge in determining

the identity of a perpetrator or whether sexual contact occurred between the victim

and the accused. Expert evidence can also be used to explain frailties in a witness’s

evidence, to corroborate the presence or absence of injuries, or to explain why victims

might recant their allegations or maintain contact with a sexual abuser.

While expert evidence plays a critical role in many cases, the conclusions drawn

by experts must not be allowed to usurp the fact-finding function of the court. This

concern is especially acute in jury cases. There is a danger that the trier of fact will

simply defer to the expert’s opinion. To avoid this danger, trial judges must control

the admissibility of expert opinion evidence, the manner in which it is presented, and

the way that evidence may be used.1

Expert witnesses have a duty to the court to give fair, objective, and non-partisan

opinion evidence.2 The absence of independence and impartiality can contribute to

a miscarriage of justice.3

This chapter will outline the general rules governing the use of expert evidence at

trial and the types of expert evidence that might be led by the Crown and the defence

in a sexual assault trial.

II. Expert Evidence: General Rules

A. Introduction

Expert opinion evidence is presumptively inadmissible. The party seeking to tender

the evidence must establish its admissibility at a voir dire held for this purpose.4 The

Crown and defence will generally be permitted to examine and cross-examine the

proposed expert at the admissibility voir dire.

At the admissibility voir dire, the tendering party is not required to demonstrate

that the facts relied upon by the expert in forming their opinion are accurate. It must

simply show that there are sucient indicia of reliability to warrant placing an opinion

based on those facts before the jury.5 The tendering party must qualify the expert in

the areas or subjects on which it hopes the expert will give evidence.6 If admitted,

the trial judge may set boundaries for the expert evidence and may even dictate the

language used by the expert in giving the proposed evidence to minimize any potential

1 Rv Abbey, 2009 ONCA 624 at paras 71-73; White Burgess Langille Inman v Abbott and

Haliburton Co, 2015 SCC 23 at para 17.

2 White Burgess Langille Inman v Abbott and Haliburton Co, ibid at para 10.

3 Rv DD, 2000 SCC 43 at para 52.

4 Rv Abbey, supra note 1 at paras 63, 71.

5 Ibid at para 130.

6 Rv Marquard, [1993] 4 SCR 223 at 243, 85 CCC (3d) 193.

© 2024 Emond Montgomery Publications. All Rights Reserved.