Canada: Environmental Consultants And Other "Participant Experts" Need Not Comply With Rule 53.03

Last Updated: April 10 2015
Article by Natalie Mullins and Niklas Holmberg

Most Read Contributor in Canada, October 2018

An issue often faced by environmental litigators is whether the client's environmental consultant hired prior to litigation should comply with rule 53.03 of the Ontario Rules of Civil Procedure. The case law has been inconsistent and provided no certainty as to how such evidence would be treated at trial.

In its decision released yesterday, the Ontario Court of Appeal in Westerhof v. Gee Estate, 2015 ONCA 206 (Westerhof) gave guidance and provided greater certainty as to how courts should treat opinion evidence from environmental consultants hired prior to litigation. The decision in Westerhof, a personal injury case, will have far-reaching importance for all litigators who wish to rely on opinion evidence of witnesses who formed opinions prior to litigation or who were not retained by a party in the litigation. 

The Decision

In Westerhof, the Court of Appeal considered the admissibility of certain opinions of medical witnesses who had treated or assessed the plaintiff after a car accident.

Justice Lederer of the Divisional Court held that, for the purpose of rule 53.03,  "[t]he important distinction is not in the role or involvement of the witness, but in the type of evidence sought to be admitted. If it is opinion evidence, compliance with rule 53.03 is required; if it is factual evidence, it is not."

Overturning the Divisional Court and ordering a new trial, the Court of Appeal disagreed that the type of evidence was determinative for the application of rule 53.03. Instead, the Court held that a witness with "special skill, knowledge, training or experience" who has not been engaged by a party to form an opinion in the litigation, may give opinion evidence for the truth of its contents without complying with rule 53.03 where:

  • The opinion to be given is based on the witness's observation of or participation in the events at issue; and
  • The witness formed the opinion to be given as part of the ordinary exercise of his or skill, knowledge, training and experience while observing or participating in such events.1

The Court developed the term "participant experts" to define a broad group of potential witnesses with special skill, knowledge or expertise that were participants in the events being considered by the court and who formed opinions in the course of those events. In contrast, the Court labeled experts "engaged by or on behalf of a party to provide [opinion] evidence in relation to a proceeding" as "litigation experts" and held that this class of experts are subject to rule 53.03. The Court reviewed the recommendations of the Osborne Report2 and the 2010 amendments to rule 53.03 and determined that they provide a "comprehensive framework addressing a specific class of expert witnesses and expert reports" and concluded that there was no basis for concluding that rule 53.03 was intended to apply to any person other than "litigation experts."

Implication for Contamination Sites Litigation

In land contamination cases, consultant experts are often hired before litigation is commenced or even contemplated. For example, a consultant may be hired by a residential property owner who wishes to re-develop their lands for commercial use. Through the investigations of the consultant, the property owner may discover that his or her lands are contaminated and there is a potential claim against the neighbour. It is not uncommon for consultants to not only identify contaminants in their report, but to also opine on the extent of contamination and its source. Accordingly, consultants have both fact and opinion evidence to provide at trial. A difficulty faced by environmental litigators is that while environmental consultants have the requisite expertise to give opinions, consultants are, by their very nature, not independent within the meaning of rule 53.03. They are hired to advise their client and have an interest in the outcome of the litigation - they do not want a Court to find that the report they generated was somehow incorrect or deficient.

This is not to suggest that an environmental consultant cannot provide objective, non-partisan evidence and have a prevailing duty to the court once in the witness box. In some cases it may be entirely appropriate to call the client's environmental consultant as a rule 53.03 expert.  In other cases, however, it simply may not be proper, practical, possible, or cost effective to have the consultant draft a new report in compliance with rule 53.03 and sign the requisite acknowledgement.

Westerhof also provides guidance for to counsel who subpoena what the Court of Appeal refers to as a "non-party expert".3 For example, a party may wish to call a hydrogeologist employed by the Ministry of the Environment and Climate Change (MOE), who reviewed reports and came to an independent conclusion on the source of contamination. The test for whether a non-party expert has to comply with rule 53.03 is the same as for a participant expert.


While not the first case to admit opinion evidence of a non-rule 53.03 expert,4 the decision in Westerhof provides clarity to litigants, including those who wish to rely on the opinions of their consultants formed before litigation was contemplated.  As long as the consultant experts are qualified to give opinion evidence and formed their opinions based on their observation of or participation in the events in issue at trial, in the normal exercise of their expertise, they are not required to comply with rule 53.03.


1 Westerhof v. Gee Estate, 2015 ONCA 206  at paras. 6 and 60 (Westerhof)

2 Civil Justice Reform Project: Summary of Findings & Recommendations (Toronto: Ontario Ministry of the Attorney General, 2007)

3 At paragraphs 6, the Court defines a "non-party expert" as one that is retained by a non-party to the litigation, who has "formed a relevant opinion based on personal observations or examinations relating to the subject matter of the litigation for a purpose other than the litigation."

4 See for example, Continental Roofing Ltd v JJ Hospitality Ltd, 2012 ONSC 1751

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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