In a civil trial, can a party “call” its opponent’s witnesses in making its case?
<p>I mean, as opposed to merely cross-examining them in the course of the opposing side’s presentation of their case.</p>
<p>A closely related question asks of calling the defendant itself, though not its  witnesses.</p>

<p><a href="/questions/tagged/ontario" class="post-tag" title="show questions tagged &#39;ontario&#39;" aria-label="show questions tagged &#39;ontario&#39;" rel="tag" aria-labelledby="tag-ontario-tooltip-container">ontario</a></p>
<p>Any party may call a witness that has relevant evidence (Rules <a href="https://www.ontario.ca/laws/regulation/900194#BK495" rel="nofollow noreferrer">53.01</a> &amp; <a href="https://www.ontario.ca/laws/regulation/900194#BK498" rel="nofollow noreferrer">53.04</a>). There is &quot;<a href="https://www.lerners.ca/lernx/expert-advice-series-no-property-in-a-witness-how-our-courts-are-applying-this-principle-to-expert-witnesses/" rel="nofollow noreferrer">no property in a witness</a>&quot; (see also <em>Unifirst Canada Ltd. c. 9766065 Canada inc.</em>, <a href="https://canlii.ca/t/jhxwd#par10" rel="nofollow noreferrer">2021 QCCQ 7946 at para. 10</a>). The adverse party may be called as a witness unless they've already testified or counsel has <a href="https://en.m.wiktionary.org/wiki/undertake" rel="nofollow noreferrer">undertaken</a> to have them appear as a witness in their case (Rule <a href="https://www.ontario.ca/laws/regulation/900194#BK501" rel="nofollow noreferrer">53.07</a>).</p>

<p>Clarence Darrow took the unusual step of <a href="https://en.wikipedia.org/wiki/Scopes_trial#Examination_of_Bryan" rel="nofollow noreferrer">calling the prosecution counsel as a witness during the Scopes Trial</a>.</p>

england-and-wales civil-procedure litigation