civil-procedure trial
Can a plaintiff call the defendant as a witness in a civil trial?
<p>Alice is suing Bob, representing herself. She has decided that her best strategy is to catch Bob in a lie to undermine his credibility.</p>
<p>Can Alice call Bob as a witness? What questions can she ask?</p>

<h2>Only in a civil case</h2>
<p>Yes, in a civil case, Alice generally can call Bob as a witness to take the stand. In many cases, this is done very early, locking in their testimony, before expert witnesses or other evidence by the plaintiff are presented to try and undermine the testimony.</p>
<p>Alice may ask only questions that have relevance to the case. Let's take for example a dispute about a contract:</p>
<ul>
<li>Alice may ask Bob if he engaged in negotiations to form the contract, about the matter of the contract, if he signed the contract, or how he (or his employees) fulfilled (or not) the contract. Pretty much everything that pertains to <em>the contract</em> or <em>the execution thereof</em>.
<ul>
<li>This does not extend to the settlement of the case or attempts thereof.</li>
</ul>
</li>
<li>Alice may not ask if Bob has an affair with Clarice unless that somehow is material to the contract at hand.</li>
<li>Alice may not re-ask questions where an objection was sustained in the same way.</li>
</ul>
<p>However, Bob might not need to answer all questions (there are things that are banned from being asked), especially as Bob's attorney will object to questions.</p>
<p>A few examples of competent questioning can be seen towards the end of My Cousin Vinnie, though this is a criminal trial.</p>
<h2>Never in a criminal trial</h2>
<p>In a criminal trial, not only can the prosecution not call Bob to the stand, he has to elect to go to the stand to even be questioned by the prosecution. That is because he can &quot;plead the 5th&quot;. <a href="https://law.stackexchange.com/a/74943/10334">There is a tiny exception for civil cases, where they can do so there too.</a></p>

<p><strong>In general, this is an “it depends” matter.</strong></p>
<h2>Germany: NO, not in civil litigation</h2>
<p>In Germany, a party cannot be witness in a civil litigation. It is a common tactic in civil litigation to silence unwanted witnesses by including them in the claim as additional defendants. (This means that you need to find a reason for suing that person as part of the same case.)</p>
<p>As the opposite of that strategy, claims are sometimes assigned to someone other than the original creditor just to allow the original creditor to testify as witness while the new creditor can act as plaintiff. Such a maneuver, however, is quite obvious which means that an original creditor has little credibility. On top of that, such a maneuver may cause the defendant to apply the strategy described above in reverse: In order to silence the original creditor as a witness, an action for a negative declaratory judgement (negative Feststellungsklage) may be filed as a third-party counterclaim (Drittwiderklage) against the original creditor. This puts the original creditor in a plaintiff-like position which they originally seeked to avoid.</p>
<h2>Germany: Victims may testify in criminal cases</h2>
<p>In penal law, however, a victim can be witness against an offender.</p>
