Helpful?
Yes No Share to Facebook

Expert Witness Report:

A Well Documented and Supported Opinion from a Subject Matter Expert



Last Updated: July 04 2026

Question: How can White Owl Legal help me prepare an expert witness report for an Ontario civil case that meets court admissibility requirements and reduces the risk the report is excluded?

Answer: White Owl Legal helps Ontario litigants and their lawyers or paralegals prepare clear, court-ready expert witness reports that satisfy the admissibility test from R. v. Mohan, 1994 CanLII 80 (SCC), 1994 SCC 80 by focusing on relevance, necessity to assist the trier of fact, the absence of an exclusionary rule, and ensuring the report is from a properly qualified expert, and then supporting the two-step approach described by White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 SCC 23.   A paralegal-led workflow helps ensure the scope is agreed up front, reviewed documents are properly attached and referenced in appendices or schedules, opinions are expressed plainly and consistently for a lay audience, the report includes a bibliography, definitions, headings, and a tidy format, and avoid bias, absolute claims, and credibility attacks that can undermine admissibility.   If you want help getting the report format and evidence support right before you file or rely on it in court, call (289) 839-3075 in Ontario to get started.

Understanding the Requirements When Preparing an Expert Witness Report Document for Court Litigation Purposes

Expert Witness Report: A Well Documented and Supported Opinion from a Subject Matter Expert A proper, well crafted, expert witness report can make the difference between success or failure within a lawsuit; and accordingly, avoiding mistakes within an expert report is of utmost importance so to ensure that the expert report is admissible, and may be relied upon, within the court proceeding. If an expert report is deemed inadmissible, such may jeopardize the legal case.

The Law
Admissibility

For a court to admit an expert report as evidence the expert report must meet the criteria of admissibility.  The criteria was summarized within the case of 2599475 Ontario Inc. v 2549445 Ontario Inc., 2023 ONSC 3508, where it was said:


[35]  The test for the admissibility of expert evidence is based on the criteria set out in R. v. Mohan, 1994 CanLII 80 (SCC), 1994 SCC 80, as follows:

a)  Relevance;

b)  Necessity in assisting the trier of fact;

c)  The absence of any exclusionary rule, apart from the opinion rule itself; and

d)  A properly qualified expert.

[36]  In White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 SCC 23, [2015] 2 S.C.R. 182, the Supreme Court divided the admissibility requirement into two distinct steps.  First, a trial judge considers the four Mohan criteria.  Then the judge balances the potential risks and benefits of admitting the expert evidence.

Quality Expert Reports
Communicate Clearly and Effectively

Prior to drafting a report, the expert should review the required scope of the report with the representative, being the lawyer or paralegal, who seeks the report.  Depending on the nature of the court case, the report may require broad details or may require a narrow focus.  In some circumstances, a brief report is adequate; and in other circumstances a more lengthy report is necessary.  Forgoing this review can result in the waste of preparing an insufficient report or the waste of preparing an excessive report.  Either is a waste of time and therefore money.

It is also necessary that the supporting evidence documents reviewed by the expert are adequately included and properly referenced. The evidence documents can, and should, include pictures, study data, testing results, among other details, all provided as attached appendices or schedules. Additionally, a bibliography to summarize any authoritative documents used for research should be included.

The report should read clearly with ease and appear professional and proofed for proper spelling, grammar, and punctuation.  The expert should write in a style directed towards the intended audience, balancing need that the report be understood by an average layperson without belittling highly intelligent judges and lawyers or other experts.  Reports should omit or limit industry specific jargon and abbreviations; but, if such is necessary, include definitions within the report.

More Hints

  • Use professional letterhead;
  • Use a cover page as well as an index or table of contents;
  • Use a curriculum vitae or resume to summarize the qualifications and credentials that confirm that the expert is genuinely an expert;
  • Use an introduction page to outline when, and from whom, the report was requested;
  • Use 12-point font and double spacing;
  • Use headings;
  • Use short, concise paragraphs;
  • Use a unique reference number for each page, table, chart, and appendix;
  • Use a definitions page or section to define technical language and industry specific jargon or abbreviations; and
  • Use an upfront summary page to outline final conclusions or opinions.

Things to Avoid

A biased or slanted expert report can be disastrous – and should be!  The expert is expected to provide opinion as a friend of the court for the primary purpose of assisting the court in the truth finding effort.  The expert, while having an opinion that may favour one litigant over another, must base the opinion on authentic reasons rather than as friend of a litigant.

  • Avoid absolute wording and phrasing;
  • Avoid words that appear as hedging or guessing;
  • Avoid critical commentary regarding credibility of other experts;
  • Avoid a scientific and clinical tone by keeping the tone friendly and personable;
  • Avoid going into details beyond the purpose of the report;
  • Avoid unnecessary adjectives or superlatives.

Summary Comment

The expert preparing an opinion report must remain attentive to the balance required when obtaining input from a legal representative whereas the lawyer or paralegal seeking the report will best understand the factual concerns and legal issues that relate to why the report is needed and can explain the desired scope; however, the findings and opinions as stated within the report must always remain the genuine unslanted view of the expert as author of the report.

At
Our Desk Now!
Need Help? Let's Get Started Today

NOTE: Do not send confidential information through the web form.  Use the web form only for your introduction.   Learn Why?
6

NOTE: A significant volume of online searches for “lawyers nearby” or “top lawyer in” typically indicates a desire for prompt and effective legal support rather than a particular label.  In Ontario, paralegals who are licensed are governed by the same Law Society that supervises lawyers and are permitted to advocate for clients in specific litigation areas.  Core to this role are advocacy, legal analysis, and procedural expertise.  White Owl Legal provides legal representation within its licensed parameters, focusing on strategic positioning, preparation of evidence, and compelling advocacy directed at securing timely and beneficial outcomes for clients.

AR, BN, CA+|EN, DT, ES, FA, FR, GU, HE, HI
IT, KO, PA, PT, RU, TA, TL, UK, UR, VI, ZH
Send a Message to: White Owl Legal

NOTE: Do not send confidential details about your case.  Using this website does not establish a legal-representative/client relationship.  Use the website for your introduction with White Owl Legal. 
Privacy Policy & Cookies | Terms of Use Your IP Address is: 216.73.216.139




Assistive Controls:  |   |  A A A