Law 101 - Expert Evidence
Expert opinion evidence is common, in fact essential in modern trials. Parties in personal injury cases are particularly reliant on medical, engineering and accounting experts to prove their own or disprove their opponent’s case. The proliferation of technical information and expert opinion evidence in court rooms has, many say, caused the expense of trials to spiral out of control and perhaps even undermine the average person’s access to justice.
We are here to briefly consider and learn about the role of experts and of expert opinion evidence in a civil – personal injury proceeding. In so doing we will briefly examine:
- The general principles of the use of expert opinion evidence;
- The substantive criteria for admissibility of an expert’s opinion;
- The procedural requirements imposed on experts giving opinion evidence in court; and
- The independent role of experts.
- General Principles
The general rule concerning what evidence can be given in court is that a witness may only give evidence of first-hand knowledge of facts gained through one of their five senses: sight, sound, smell, taste and touch.
One exception to this rule is that appropriately qualified “experts” may be permitted to tender their opinions premised on hypothetical facts. The purpose of this is for the trier of fact to have a ready-made inference to draw from the underlying facts which the party must also prove as the foundation for the expert’s opinion.
An expert’s opinion evidence may be necessary to allow a judge or a jury to draw an enlightened inference or conclusion which they could not otherwise be capable of drawing, absent having benefit of an expert’s special knowledge of the subject-matter.
- Substantive Criteria for Admissibility of An Expert Opinion
The Supreme Court of Canada in the cases of R. v. Mohan
and R. v. J. (J.-L.)
set out a four part test for admissibility of expert opinion evidence. For the opinion evidence of an expert to be admissible it must:
- be relevant to an issue in the case;
- be necessary to assist the trier of fact;
- not contravene an exclusionary rule; and
- be given by a properly qualified expert.
The trial judge is a gate keeper for determining admissibility of expert opinion evidence. The further afield from conventional, agreed upon standards of specialized knowledge the expert proposes to give evidence on, the more the court will question the necessity of that evidence in light of its reliability.
For what appear to be novel scientific ideas to be presented in evidence the court will apply a four part test to determine their reliability:
- whether the expert’s theory can or has been tested;
- whether the theory has withstood peer review and publication;
- whether there is a known or potential rate of error or the existence of standards to test the application of the tendered theory or technique; and
- whether the theory has generally been accepted by the relevant scientific community.
In order for the expert to be permitted to give opinion evidence he or she must be recognized by the court as properly qualified to give the opinion evidence they propose to tender. The proposed expert witness must:
- have special skill or peculiar knowledge through study or experience in respect of the subject matter of the opinion;
- have expertise in the particular field in which the opinion is sought;
- confine their opinion evidence to the expert’s area of expertise;
This is the scope of the substantive threshold for acceptable expert opinion evidence. In order for a party to tender expert evidence the party tendering that evidence must comply with certain procedural requirements.
1. Procedural Requirements for Admissibility of Expert Evidence
The Rules of Civil Procedure create certain required steps that must be taken prior to a person being tendered to give expert evidence in a trial. Essentially if a party wishes to call an expert that party must have their proposed expert witness provide an up to date CV and write a report containing:
- The expert’s name, address and area of expertise;
- The expert’s germane qualifications, education and experience;
- The instructions provided to the expert by the instructing counsel;
- The nature of the opinion sought and each issue in the proceeding to which the opinion relates;
- The expert’s opinion respecting each issue and, where there is a range of opinions given, a summary of the range of opinions and the reasons for the expert’s opinion within that range;
- The expert’s reasons for his or her opinion, including:
- A description of the factual assumptions on which the opinion is based,
- A description of any research conducted by the expert that led him or her to form the opinion, and
- A list of every document, if any, relied on by the expert in forming the opinion.
- An acknowledgement of expert’s duty (form 53) signed by the expert.
The report an expert writes is notice of that expert’s intended opinion evidence at trial. Once called to give evidence an expert may be confined to the four corners of the content of the report and may be cross-examined on the contents of the report. Straying in testimony beyond the scope of the report; not accounting for relevant material; imprecisely defining the issues you are addressing; not providing appropriate reference to the underlying information, factual assumptions or source data supporting the opinion weakens the strength of the opinion report and opens avenues of cross-examination for the opposing counsel.
2. Independence and Impartiality of Experts
In Ontario under Rule 53.03 it is a requirement for all persons who write an expert opinion report to also sign a Form 53 A (attached). Paragraph 3 in that form sets out the duty of an expert to the court when that expert gives his or her evidence. The duties set out in that paragraph were first and best laid out in an English shipping case involving a ship which ran aground on a shoal off the coast of Sierra Leone called the Ikarian Reefer
. In that case the court said:
“The duties and responsibilities of expert witnesses in civil cases include the following:
1. Expert evidence presented to the Court should be and should be seen to be the independent product of the expert uninfluenced as to form or content by the exigencies of litigation...
2. An expert witness should provide independent assistance to the Court by way of objective unbiased opinion in relation to matters within his expertise...An expert witness in the High Court should never assume the role of advocate.
3. An expert witness should state the facts or assumptions on which his opinion is based. He should not omit to consider material facts which detract from his concluded opinion...
4. An expert witness should make it clear when a particular question or issue falls outside his expertise.
5. If an expert’s opinion is not properly researched because he considers that insufficient data is available then this must be stated with an indication that the opinion is no more than a provisional one...
6. If after exchange of reports, an expert witness changes his view on a material matter...such change of view should be communicated...to the other side without delay and when appropriate to the Court.
7. Where expert evidence refers to photographs, plans, calculations...survey reports or other similar documents there must be provided to the opposite party at the same time as the exchange of reports...”
The significance of these principles is that, especially for treating health professionals who are called to give expert opinion evidence, such witnesses may be put in an uncomfortable situation. Physicians for example are subject to a Practice Guide in which certain duties physicians are obliged to observe are set out. One is for physicians to advocate for their patients. The Practice Guide, Item A6 states:
“Advocacy is an important component of the doctor-patient relationship; physicians should, individually and collectively, advocate for their patients. Advocacy involves the responsible use of expertise and influence to advance a patient’s health care interests.”
Physicians for example are expected to be advocates for their patients. They cannot however, be advocates for their patients when giving expert opinion evidence. They must be fair, objective, and non-partisan. They must also limit their evidence to areas within their field of expertise.
We have provided this brief paper to give you a brief oversight of the law of expert opinion evidence so that when you are asked to write an expert opinion report and give expert opinion evidence you will be familiar with the framework and environment in which it is to be given.
The Law of Evidence in Canada 3rd
Ed., Sopinka, Lederman &Bryant, LexisNexis Canada Inc., Toronto 2009, at p. 785
 R. v. Abbey,
 2 S.C.R. 24
 R. v. K. (A.)
(1999), O.R. (3d) 641 (C.A.)
 The “Ikarian Reefer”,
Lloyd’s Law Reports  Vol. 2 p. 69
Ontario College of Physicians and Surgeons Practice Guide (2007), p. 12