Police Experts

• Author: Eric V. Gottardi/Jennifer A. MacLellan/Michael Lacy/Robin Flumerfelt
• Pages: 145-177

145

7

Police

Experts

I. Overview ................................................ 146

II. Common Grounds for Challenging Expert PoliceWitnesses ....... 146

A. Bias .............................................. 146

B. On-the-Job Experience ............................... 150

C. Anecdotal Evidence .................................. 151

III. Specific Types of Police Experts .............................. 154

A. Use of Force Experts ................................. 154

B. Criminal Organization and Gang Experts ................ 161

C. Drug Experts ....................................... 165

IV. Bloodstain Pattern Analysis ................................. 169

A. Relevance of Bloodstain Pattern Analysis to Issues at Trial ... 171

B. Admissibility Issues of Bloodstain Pattern Analysis ........ 171

V. Accident Reconstruction ................................... 173

A. The Accident Reconstruction Expert .................... 174

B. Admissibility Issues ................................. 175

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146Part II Specific Types of Expert Evidence

I. Overview

Police officers with specific expertise obtained during their employment are regularly

qualified as expert witnesses by criminal courts. Police officers have testified as expert

witnesses in numerous capacities, on topics as varied as bloodstain analysis; use of

force; the characteristics of criminal organizations; the methods, hierarchy, and ter-

minology of the drug trade; and accident reconstruction. Given that they tend to be

Crown witnesses (although not exclusively) and that their “day job” is to investigate

crime, the admissibility of evidence from police experts is often challenged on the

basis of bias in favour of the prosecution. Other common bases for challenge of police

expert witnesses include the fact that the nature of their expertise tends to be prac-

tically derived and experience based as opposed to academically achieved, and their

evidence can be anecdotal. This chapter will explore each of these issues along with

some examples of the specific types of police expert witnesses often encountered.

II. Common Grounds for Challenging Expert

PoliceWitnesses

A. Bias

In White Burgess Langille Inmanv Abbott and Haliburton Co,1 the Supreme Court

of Canada clarified that to be properly qualified, an expert must be impartial, in-

dependent, and unbiased.2 The “acid test” is whether an expert’s evidence would

remain the same regardless of which party retained the witness. However, the Court

also recognized the realities of adversarial litigation: “Experts are generally retained,

instructed and paid by one of the adversaries. These facts alone do not undermine the

expert’s independence, impartiality and freedom from bias.”3

An expert’s independence and impartiality go both to admissibility of the proposed

evidence and the weight it should be given. The proposed expert must testify or attest

to understanding the expert’s duty to the court to be fair, objective, and non-partisan.4

While this is a low threshold, it does not equate to automatic admissibility, and evi-

dence on the expert’s understanding is required.5White Burgess explained the process

as follows:

1 2015 SCC 23.

2 Ibid at para 32.

3 Ibid at para 32.

4 Ibid at para 47.

5 In R v Patterson, 2020 NSSC 151, the expert toxicologist had not been asked whether she

understood her duty of impartiality to the Court. If the Crown forgets to ask the direct ques-

tion, counsel can request an inference to be drawn from other evidence, but the Summary

Conviction Appeal Court found the trial judge in that case did not err in concluding that an

inference of impartiality could not be drawn on the basis of the evidence before him.

© [2022] Emond Montgomery Publications. All Rights Reserved.

Chapter 7 Police Experts 147

Once the expert attests or testifies on oath to this effect, the burden is on the party

opposing the admission of the evidence to show that there is a realistic concern that the

expert’s evidence should not be received because the expert is unable and/or unwilling

to comply with that duty. If the opponent does so, the burden to establish on a balance of

probabilities this aspect of the admissibility threshold remains on the party proposing to

call the evidence. If this is not done, the evidence, or those parts of it that are tainted by

a lack of independence or by impartiality, should be excluded. This approach conforms

to the general rule under the Mohan framework, and elsewhere in the law of evidence,

that the proponent of the evidence has the burden of establishing its admissibility.6

White Burgess is clear that “this threshold requirement is not particularly onerous,

and it will likely be quite rare that a proposed expert’s evidence would be inadmissible

for failing to meet it.”7 The Court explained that

it is the nature and extent of the interest or connection with the litigation or a party

thereto which matters, not the mere fact of the interest or connection; the existence

of some interest or a relationship does not automatically render the evidence of the

proposed expert inadmissible. In most cases, a mere employment relationship with the

party calling the evidence will be insufficient to do so. On the other hand, a direct finan-

cial interest in the outcome of the litigation will be of more concern. The same can be

said in the case of a very close familial relationship with one of the parties or situations in

which the proposed expert will probably incur professional liability if his or her opinion

is not accepted by the court. Similarly, an expert who, in his or her proposed evidence or

otherwise, assumes the role of an advocate for a party is clearly unwilling and/or unable

to carry out the primary duty to the court. I emphasize that exclusion at the threshold

stage of the analysis should occur only in very clear cases in which the proposed expert

is unable or unwilling to provide the court with fair, objective and non-partisan evidence.

Anything less than clear unwillingness or inability to do so should not lead to exclusion,

but be taken into account in the overall weighing of costs and benefits of receiving the

evidence.8

Previously, apparent bias might have been enough to show an expert police witness

was unsuitable. White Burgess,however, is clear: apparent bias is insufficient; actual

bias must be shown.9

Once the threshold inquiry is surmounted, the expert’s independence and impar-

tiality will still be considered at the second gatekeeping stage when the judge weighs

the overall competing considerations to admitting the evidence.10 Crown attorneys

6 White Burgess, supra note 1 at para 48.

7 Ibid at para 49.

8 Ibid at para 49.

9 Ibid at para 50.

10Ibid at para 54.

© [2022] Emond Montgomery Publications. All Rights Reserved.