Expert Evidence: When You Need an Expert in a Civil Case

In many civil cases, a judge needs an expert's opinion to decide a technical question, for example why a roof leaked or what a repair should cost.

When you might need one

• Construction and renovation: was the work defective, and what will it cost to fix?
• Vehicles: what caused a breakdown?
• Injuries: what is the injury and its effect?
• Property value: what is something worth?

The expert's duty

In Ontario, an expert's duty is to the court: to give opinion evidence that is fair, objective and non-partisan.

In Small Claims Court

Expert evidence often comes in as a written report or statement served in advance under the Small Claims Court rules, which can save the cost of the expert attending.

In the Superior Court

Expert reports must meet detailed requirements under the Rules of Civil Procedure, including the expert's qualifications, the facts relied on, and an acknowledgment of their duty.

Choosing an expert

• Relevant qualifications and experience
• Independence from you and the case
• A clear written report with reasons

Sources

• Rules of the Small Claims Court
• Rules of Civil Procedure (Ontario)

Read next: Can't Afford Court Fees? Ontario's Fee Waiver

General Ontario legal information, not legal advice for your matter, and reading it does not create a retainer. Sources checked 16 October 2026: check the current law, forms and dates before you act.

Photos from Unsplash: Books related to law and human rights are visible · Empty ornate courtroom interior with wooden paneling and green seats.

This article is general information for people in Ontario, not legal advice. Rules, forms and deadlines change, and every situation is different. Check the current rule or speak to a licensed legal professional before you act.