Canada: Do Experts Always Have To Produce A Report To Give An Opinion At Trial?

Last Updated: March 31 2015
Article by Marco P. Falco

The Ontario Court of Appeal has held that non-party and "participant" experts may give opinion evidence at trial without necessarily having to comply with the rules governing ordinary litigation experts.

In Westerhof v. Gee, 2015 ONCA 206, per Simmons J.A., the Court heard two appeals from two claims resulting from two separate car accidents. In both cases, the defendants had admitted liability and the trials concerned whether the accidents led to the plaintiffs' injuries and the amount of damages.

In the Westerhof action, the trial judge ruled opinion evidence concerning the history, diagnosis and prognosis of various medical practitioners inadmissible. According to the trial judge, the evidence of these witnesses constituted "opinion evidence" and thus had to comply with Rule 53.03 of the Rules of Civil Procedure, which requires, amongst other things, that the expert provide a report setting out his or her findings and signing an acknowledgment of the expert's duty of impartiality to the Court. On appeal to the Divisional Court, the plaintiff argued that the trial judge erred in his evidentiary rulings by failing to distinguish between the opinion evidence given by litigation experts, i.e. those experts retained by the parties for the purposes of the litigation, and the opinion evidence given by "participant" and non-party expert witnesses. The Divisional Court dismissed the plaintiff's appeal and held that if the evidence at issue was opinion evidence, compliance with Rule 53.03 was required.

In the McCallum action, the trial judge permitted several medical practitioners who treated the plaintiff to give opinion evidence concerning the plaintiff's future employment prospects and future treatment, without requiring those practitioners to comply with Rule 53.03. According to the trial judge, these witnesses could give opinion evidence without complying with Rule 53.03 because they were treating medical practitioners.

On appeal to the Court of Appeal, the Court held that in the Westerhof action, the trial judge erred in holding as a general rule that various medical practitioners who treated the plaintiff could not give opinion evidence because they did not comply with Rule 53.03. The jury's verdict and trial judge's judgment were set aside and a new trial was ordered. In the McCallum appeal, the Court held that permitting the opinion evidence of medical practitioners without compliance with Rule 53.03 was not unfair. Accordingly, the McCallum appeal was dismissed.

In making these rulings, the Court of Appeal established a number of critical principles as to when the opinion evidence of non-litigation experts will be admissible, absent compliance with Rule 53.03. These principles are as follows:

1. There are three (3) classes of experts who may testify at trial.

The Court identified three classes of experts who may testify at trial. This classification is essential to determining whether the expert is required to comply with Rule 53.03, as set out below. First, the Court recognized the existence of what it calls "litigation experts", i.e. those who are retained by a party for the purposes of the litigation and who the party intends to call as an expert at trial. According to the Court, litigation experts are required to comply with Rule 53.03 and provide a report if the party intends to call that expert at trial. Second, the Court recognized the existence of what it called "participant experts", i.e. those witnesses whose evidence is derived from their observations or involvement in the underlying facts. Participant experts may include witnesses such as treating physicians in a personal injury case, accident reconstruction engineers, or the fire marshals who investigated a fire. The third type of witness is the "non-party expert", i.e. those experts hired by a non-party and who have formed a relevant opinion based on personal observations or examinations relating to the subject-matter of the litigation. Non-party experts may include those who, for example, provide long-term disability or accident benefits opinions, but whose reports are being used in a different proceeding.

2. Participant experts and Non-Party experts may testify at trial without having complied with Rule 53.03.

The Court held that both participant experts and non-party experts with special skill, knowledge, training or experience, who have not been engaged by or on behalf of a party to the litigation, may give opinion evidence for the truth of its contents without complying with Rule 53.03. This opinion evidence may be given so long as:

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

However, where participant experts or non-party experts give opinion evidence that extends beyond the limits set out in paragraphs (a) and (b) above, they must comply with Rule 53.03 with respect to the "portion of their opinions extending beyond those limits".

According to the Court, the trier of fact retains his or her "gatekeeper" function in relation to opinion evidence. Thus, a Court may, if the evidence did not meet the test for admissibility, exclude all or part of the opinion evidence of a participant expert or non-party expert or rule that all or part of such evidence is not admissible for the truth of its contents. The Court may also require the participant or non-party expert to comply with Rule 53.03 if the opinion offered goes beyond the scope of the opinion formed in the "course of treatment or observation for purposes other than the litigation".

3. There are good reasons for allowing participant and non-party experts to proffer opinion evidence without having to comply with Rule 53.03.

In analyzing why it was appropriate to allow participant experts and non-party experts to offer opinion evidence at trial without having to, amongst other things, file a Rule 53.03 report and sign an acknowledgement of the expert's duty of impartiality to the Court, the Court of Appeal offered a number of rationales. They include:

  1. Prior to the amendments to the Rules of Civil Procedure in 2010, Ontario case law was clear that Rule 53.03 did not apply to opinion evidence given by participant experts. The Court of Appeal's ruling in Westerhof is consistent with previous case law and confirms that the amendments to the Rules ushered in 2010 did not represent a normative shift in the way expert evidence is to be treated at trial;
  2. Ontario case law issued after the amendments to the Rules of Civil Procedure in 2010 does not support the view that participant and non-party experts are obliged to comply with Rule 53.03;
  3. Nothing in the report of the Honourable Coulter Osborne, Q.C. (the "Osborne Report"), which led to the amendments to the Rules of Civil Procedure in 2010, indicated an intention to address participant experts or non-party experts. The problems identified in the Osborne Report, i.e. relating to an "industry of competing experts", related to litigation experts, not participant experts or non-party experts;
  4. The text of the 2010 amendments to the Rules governing experts support the view that Rule 53.03 does not apply to participant or non-party experts. For example, Rule 4.1, the new "Duty of Expert" rule, requires an objective, fair and non-partisan opinion from "every expert engaged by or on behalf of a party". Rule 53.03 also speaks of experts "engaged by or on behalf of a party". The Court thus concluded that Rules 4.1 and Rule 53 create a comprehensive framework addressing a specific class of expert witness and expert report. They were intended to apply to experts engaged by or on behalf of a party;
  5. There are no serious disclosure problems that exist in relation to the opinions of participant experts and non-party experts, such that it would require them to comply with Rule 53.03:

    In many instances, these experts will have prepared documents summarizing their opinions about the matter contemporaneously with their involvement. These summaries can be obtained as part of the discovery process. Further, even if these experts have not prepared such summaries, it is open to a party, as part of the discovery process, to seek disclosure of any opinions, notes, or records of participant experts and non-party experts the opposing party intends to rely on at trial...
  6. Not requiring participant and non-expert witnesses to file Rule 53.03 reports will minimize expense and delay. Requiring these types of experts to file reports would actually lead to further expense and delay. Participant experts and non-party experts are not paid an expert's fee to write a report. Rather, they testify because they are involved in the underlying events and have already documented their opinions. Requiring them to produce Rule 53.03 reports would only increase the cost of litigation.

The Court's ruling ensures that all experts provide objective, fair evidence at trial and that participating and non-party experts are not unduly burdened by the requirements of Rule 53.03.

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.

To print this article, all you need is to be registered on

Click to Login as an existing user or Register so you can print this article.

Marco P. Falco
In association with
Related Video
Up-coming Events Search
Font Size:
Mondaq on Twitter
Register for Access and our Free Biweekly Alert for
This service is completely free. Access 250,000 archived articles from 100+ countries and get a personalised email twice a week covering developments (and yes, our lawyers like to think you’ve read our Disclaimer).
Email Address
Company Name
Confirm Password
Mondaq Topics -- Select your Interests
 Law Performance
 Law Practice
 Media & IT
 Real Estate
 Wealth Mgt
Asia Pacific
European Union
Latin America
Middle East
United States
Worldwide Updates
Check to state you have read and
agree to our Terms and Conditions

Terms & Conditions and Privacy Statement (the Website) is owned and managed by Mondaq Ltd and as a user you are granted a non-exclusive, revocable license to access the Website under its terms and conditions of use. Your use of the Website constitutes your agreement to the following terms and conditions of use. Mondaq Ltd may terminate your use of the Website if you are in breach of these terms and conditions or if Mondaq Ltd decides to terminate your license of use for whatever reason.

Use of

You may use the Website but are required to register as a user if you wish to read the full text of the content and articles available (the Content). You may not modify, publish, transmit, transfer or sell, reproduce, create derivative works from, distribute, perform, link, display, or in any way exploit any of the Content, in whole or in part, except as expressly permitted in these terms & conditions or with the prior written consent of Mondaq Ltd. You may not use electronic or other means to extract details or information about’s content, users or contributors in order to offer them any services or products which compete directly or indirectly with Mondaq Ltd’s services and products.


Mondaq Ltd and/or its respective suppliers make no representations about the suitability of the information contained in the documents and related graphics published on this server for any purpose. All such documents and related graphics are provided "as is" without warranty of any kind. Mondaq Ltd and/or its respective suppliers hereby disclaim all warranties and conditions with regard to this information, including all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement. In no event shall Mondaq Ltd and/or its respective suppliers be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use or performance of information available from this server.

The documents and related graphics published on this server could include technical inaccuracies or typographical errors. Changes are periodically added to the information herein. Mondaq Ltd and/or its respective suppliers may make improvements and/or changes in the product(s) and/or the program(s) described herein at any time.


Mondaq Ltd requires you to register and provide information that personally identifies you, including what sort of information you are interested in, for three primary purposes:

  • To allow you to personalize the Mondaq websites you are visiting.
  • To enable features such as password reminder, newsletter alerts, email a colleague, and linking from Mondaq (and its affiliate sites) to your website.
  • To produce demographic feedback for our information providers who provide information free for your use.

Mondaq (and its affiliate sites) do not sell or provide your details to third parties other than information providers. The reason we provide our information providers with this information is so that they can measure the response their articles are receiving and provide you with information about their products and services.

If you do not want us to provide your name and email address you may opt out by clicking here .

If you do not wish to receive any future announcements of products and services offered by Mondaq by clicking here .

Information Collection and Use

We require site users to register with Mondaq (and its affiliate sites) to view the free information on the site. We also collect information from our users at several different points on the websites: this is so that we can customise the sites according to individual usage, provide 'session-aware' functionality, and ensure that content is acquired and developed appropriately. This gives us an overall picture of our user profiles, which in turn shows to our Editorial Contributors the type of person they are reaching by posting articles on Mondaq (and its affiliate sites) – meaning more free content for registered users.

We are only able to provide the material on the Mondaq (and its affiliate sites) site free to site visitors because we can pass on information about the pages that users are viewing and the personal information users provide to us (e.g. email addresses) to reputable contributing firms such as law firms who author those pages. We do not sell or rent information to anyone else other than the authors of those pages, who may change from time to time. Should you wish us not to disclose your details to any of these parties, please tick the box above or tick the box marked "Opt out of Registration Information Disclosure" on the Your Profile page. We and our author organisations may only contact you via email or other means if you allow us to do so. Users can opt out of contact when they register on the site, or send an email to with “no disclosure” in the subject heading

Mondaq News Alerts

In order to receive Mondaq News Alerts, users have to complete a separate registration form. This is a personalised service where users choose regions and topics of interest and we send it only to those users who have requested it. Users can stop receiving these Alerts by going to the Mondaq News Alerts page and deselecting all interest areas. In the same way users can amend their personal preferences to add or remove subject areas.


A cookie is a small text file written to a user’s hard drive that contains an identifying user number. The cookies do not contain any personal information about users. We use the cookie so users do not have to log in every time they use the service and the cookie will automatically expire if you do not visit the Mondaq website (or its affiliate sites) for 12 months. We also use the cookie to personalise a user's experience of the site (for example to show information specific to a user's region). As the Mondaq sites are fully personalised and cookies are essential to its core technology the site will function unpredictably with browsers that do not support cookies - or where cookies are disabled (in these circumstances we advise you to attempt to locate the information you require elsewhere on the web). However if you are concerned about the presence of a Mondaq cookie on your machine you can also choose to expire the cookie immediately (remove it) by selecting the 'Log Off' menu option as the last thing you do when you use the site.

Some of our business partners may use cookies on our site (for example, advertisers). However, we have no access to or control over these cookies and we are not aware of any at present that do so.

Log Files

We use IP addresses to analyse trends, administer the site, track movement, and gather broad demographic information for aggregate use. IP addresses are not linked to personally identifiable information.


This web site contains links to other sites. Please be aware that Mondaq (or its affiliate sites) are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of these third party sites. This privacy statement applies solely to information collected by this Web site.

Surveys & Contests

From time-to-time our site requests information from users via surveys or contests. Participation in these surveys or contests is completely voluntary and the user therefore has a choice whether or not to disclose any information requested. Information requested may include contact information (such as name and delivery address), and demographic information (such as postcode, age level). Contact information will be used to notify the winners and award prizes. Survey information will be used for purposes of monitoring or improving the functionality of the site.


If a user elects to use our referral service for informing a friend about our site, we ask them for the friend’s name and email address. Mondaq stores this information and may contact the friend to invite them to register with Mondaq, but they will not be contacted more than once. The friend may contact Mondaq to request the removal of this information from our database.


This website takes every reasonable precaution to protect our users’ information. When users submit sensitive information via the website, your information is protected using firewalls and other security technology. If you have any questions about the security at our website, you can send an email to

Correcting/Updating Personal Information

If a user’s personally identifiable information changes (such as postcode), or if a user no longer desires our service, we will endeavour to provide a way to correct, update or remove that user’s personal data provided to us. This can usually be done at the “Your Profile” page or by sending an email to

Notification of Changes

If we decide to change our Terms & Conditions or Privacy Policy, we will post those changes on our site so our users are always aware of what information we collect, how we use it, and under what circumstances, if any, we disclose it. If at any point we decide to use personally identifiable information in a manner different from that stated at the time it was collected, we will notify users by way of an email. Users will have a choice as to whether or not we use their information in this different manner. We will use information in accordance with the privacy policy under which the information was collected.

How to contact Mondaq

You can contact us with comments or queries at

If for some reason you believe Mondaq Ltd. has not adhered to these principles, please notify us by e-mail at and we will use commercially reasonable efforts to determine and correct the problem promptly.