Rule 5.605 Judge’s competency as a witness

The judge running a trial cannot also take the witness stand to give testimony in that same case. Judges are there to oversee the proceedings and make rulings, not to provide evidence or facts about what happened.

This rule also protects the parties involved without them having to do anything extra. Normally, if a lawyer wants to challenge something that happens in court, they have to speak up and object right away, or they lose the right to complain about it later. But with this rule, that step is not necessary. If a judge tries to testify as a witness, the problem is automatically preserved for appeal, even if no one objected at the time.