Opinion Evidence: General Principles and More

• Author: Mr. Justice Alan W. Bryant
• Pages: 507-513

Opinion

Evidence:

General Principles

and

More

Mr.

Justice Alan

W.

Bryant*

A.

INTRODUCTION

In

this

lecture,

I

will discuss

the

modern rule governing

the

admissibility

of

the

opinion

of

experts.

I

will review

the

general principles

of

admissi-

bility

and

then comment

on the

reformulated

Mohan

criteria

of

relevance,

reliability,

necessity,

the

cost-benefit analysis,

the

absence

of an

exclusion-

ary

rule,

and the

requirement

of a

properly qualified

expert.1

B.

GENERAL

PRINCIPLES

Lay

witnesses must

possess

firsthand knowledge

of

their evidence.

They

testify

about historical

facts

that they perceived through their

senses

of

sight,

smell,

hearing, taste,

and

touch. Expert

witnesses,

on the

other hand, have specialized knowledge

or

skill

and it is not

necessary

for

them

to

have firsthand knowledge. Experts provide

the

fact-finder

with

a

ready-made inference that they

are

able

to

formulate

by

virtue

of

*

Of the

Superior Court

of

Justice,

Ontario. Formerly

of the

Faculty

of

Law, Uni-

versity

of

Western Ontario; McCarthy

Tetrault

LLP.

1 See

Sopinka,

Lederman,

and

Bryant,

The Law

of

Evidence

in

Canada,

2d ed.

(Markham,

ON:

Butterworths,

1999) Chapter

12,

at

616-24

and the

Supple-

ment

to the 2d

edition

(forthcoming

spring

2004)

for a

more comprehensive

analysis

of the

topic.

507