Weilers LLP

Excluding Witnesses

Excluding Witnesses

August 8, 2023

By Brian Babcock

Ontario’s Rules of Civil Procedure provide for an order excluding witnesses who have not yet testified at trial. This order is made automatically at the request of any party. The purpose of the rule is to ensure that later witnesses do not tailor their evidence to match that of earlier witnesses and that there can be an assessment by the trial judge of the credibility of the later witnesses untainted by concerns about the tailoring of evidence.


What if no order excluding witnesses is made, and it is discovered that some witnesses observed the proceedings via Zoom before they testified?


In 2505243 Ontario Limited o/a ByPeterandPaul.com v. Princes Gate GP Inc. et al., that was the issue that faced the trial judge. Several Plaintiff witnesses had watched the trial unfold in a boardroom at the lawyers’ office. Upon learning of this, the Defendant moved for a mistrial, which would have meant starting the trial over (it was on day six) and creating further issues about how to treat the evidence of the “tainted” witnesses.

The judge did not allow a mistrial. No order excluding witnesses had been made, and the judge carefully considered the effect of the later witnesses seeing earlier evidence as to how she would assess their evidence. She decided that there was no harm, so the trial proceeded to its conclusion.

The Ontario Court of Appeal agreed with that decision, stating that:

[37] Neither party sought an order excluding witnesses. In her mistrial ruling, the trial judge said that, although she found the situation concerning, it was not so egregious that it would require the extreme remedy of either a mistrial or the striking of evidence. After the trial, the trial judge noted in her judgment that, “in retrospect, while the issue was very concerning when first raised, in the end, it is not one which would change this Court’s view with respect to the reliability of the testimony of the impugned witnesses.”


  • If you want witnesses excluded – and you should- remember to ask for an order excluding witnesses.
  • Even in Small Claims Court, where there is no Rule to exclude witnesses, judges will usually exclude witnesses if asked to do so. It makes the judge’s job easier.
  • If the trial is via Zoom (or a hybrid of Zoom and live), be aware of who is observing.
  • If there is no ordered exclusion, the judge will still be concerned about the impact of later witnesses seeing earlier evidence.
  • A mistrial is an extreme remedy, seldom granted.
  • Before ordering a mistrial, the judge should carefully consider the impact on trial fairness of the situation.


As part of our “proud tradition,” the litigation team at Weilers LLP knows the Rules and how to use them in our client’s favour. Our “progressive approach” means that we stay current on recent developments, including the unwritten rules as to what values judges apply in court – principally, the predominance of fairness over black letter rules.

If you are looking for ethical, experienced, knowledgeable lawyers in Thunder Bay or Northwestern Ontario, give Weilers LLP a call and see if we are the right lawyers for you.