Canada: Ontario Court Of Appeal Affirms Trial Judges As 'Robust Gatekeepers' Of Expert Evidence

Last Updated: March 10 2015
Article by Colin Chant

In the face of the trend in litigation towards an ever greater reliance on expert evidence, the recent Ontario Court of Appeal decision in Meady v Greyhound Canada Transportation Corp. 2015 ONCA 6 ("Meady") upholding a trial judge's decision to exclude the evidence of two of the plaintiffs' expert witnesses on the grounds that their evidence was not necessary, signals to litigants and lower courts alike the expectation that trial judges will act as robust gatekeepers to control the admission of expert evidence, and that their decisions to exclude expert evidence will be given deference.


In December of 2000, Shaun Davis, a 21-year-old passenger of a Greyhound bus driving through Northern Ontario, left his seat and grabbed the steering wheel from the bus driver, causing the bus to veer off the road and topple on its side, killing one passenger and injuring many others.

Mr. Davis suffered from paranoid delusions, and prior to boarding the bus had interacted with two OPP officers who found him to be displaying signs of anxiety and paranoia but who nonetheless concluded that he did not pose a threat to anyone. The police officers told the bus driver about Mr. Davis' paranoia; however, the driver allowed Mr. Davis to board the bus, and let him sit up front.

After the accident, a number of the passengers commenced an action naming Greyhound, the bus driver, the two OPP officers and the OPP.

The matter went to trial in 2010, and after 65 days of evidence from 83 witnesses, Justice Platana dismissed the action against all of the defendants except Davis.

The plaintiffs appealed.

At issue on the appeal was the decision by Justice Platana at trial to exclude the evidence of two expert witnesses tendered by the plaintiffs: a retired police officer who opined that the OPP officers had failed to meet the standard of care of reasonable and prudent officers by failing to detain Mr. Davis under the Mental Health Act or the common law doctrine of investigative detention; and a transportation safety consultant who had experience as an accident investigator and in drafting policies and standards for training bus drivers who opined that the bus driver was negligent in his operation of the bus.

Exclusion of Expert Evidence at Trial

At trial, Justice Platana excluded the evidence of the retired police officer on the basis that while expert evidence concerning the standard of care of professionals such as police officers may be required in some cases, it was not required where the issue falls within the understanding or experience of the trier of fact, and that because evidence regarding police policies and procedures was adduced into evidence, the officers could be cross-examined on their compliance.

Justice Platana found the evidence of the transportation safety consultant relevant but excluded it as unnecessary, after concluding that he did not need expert evidence to determine what the driver knew or ought to have known about his duties as an operator, how fast he should have been driving, how he should have reacted to Mr. Davis grabbing the wheel or the steps he could have taken to avoid the accident. Justice Platana also noted as a factor in his decision to exclude the evidence that the consultant had expressed an opinion on the ultimate issue by specifically stating in his report that the bus driver was negligent in the operation of the bus.

Principles Governing the Admissibility of Expert Evidence

The test governing the admissibility of expert evidence was articulated in the Supreme Court of Canada's decision in R v Mohan where the court held that expert evidence:

  1. must be relevant;
  2. must be necessary to assist the trier of fact;
  3. must not be subject to an exclusionary rule; and
  4. the expert must be properly qualified

At issue in Meady was whether the proposed expert evidence was necessary to assist the trier of fact.

The application of the necessity criterion asks whether the trier of fact is able to form a correct judgment about the issue without the assistance of persons with special knowledge.

In considering necessity, the Court of Appeal noted the growing recognition of the responsibility of trial judges to exercise a more robust gatekeeper role in the admission of expert evidence, and the admonition by the Supreme Court in Masterpiece Inc. v Alavida Lifestyles Inc. that unnecessary expert evidence distracts triers of fact from the issues at hand, complicates the proceeding, prolongs the trial and increases the cost of litigation. The Court also cited the growing importance of "trial economy", and the need for judges to conduct a cost-benefit analysis when considering whether to admit evidence.

The Court further held that because there is no "bright line" to determine whether the subject matter of expert evidence falls within the normal experience of a particular trier of fact, deference is owed to the exercise of the trial judge's gatekeeper function in excluding unnecessary evidence. The trial judge is best equipped to appreciate the issues in the context of the evidence as it unfolds and to determine the extent to which, if at all, expert evidence is required to assist the trier of fact in the disposition of the issues.

Reasons for Judgment

In applying the principles outlined above, the Court of Appeal found that Justice Platana was uniquely positioned to decide whether he needed expert evidence, and that his rulings on the excluded evidence attracted deference.

With respect to the retired police officer, the Court found that the exercise of police powers of investigation, arrest and detention are "part of the daily diet" of Superior Court judges and it was open to Justice Platana to conclude, as he did, that expert evidence was not required for him to determine whether the OPP officers in question should have conducted further investigation of, restrained or otherwise diverted Mr. Davis from boarding the bus.

The Court also held that Justice Platana had reasonably excluded the evidence of the transportation safety consultant and issues similar to those raised by the consultant were frequently decided in motor vehicle negligence cases without the assistance of expert evidence, and his conclusions regarding the bus driver's actions were available to him on the evidence before him and could be decided without expert evidence.

The appeal was dismissed.

Why the Decision Matters

The Court of Appeal's decision in Meady strongly that suggests that trial judges will be casting an increasingly critical eye on whether to exclude the evidence of persons proffered as experts at trial and that their decisions in this regard will be given deference by higher courts.

The decision also serves as a stark reminder that just because an expert has evidence that is relevant does not mean that it will always be necessary.

Parties preparing for trial would do well to take note of this decision.

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.

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.