Rule 605 Judge's Competency as a Witness

The judge running a trial cannot also take the witness stand and testify as a witness in that same case. These are two different jobs, and one person cannot do both at the same time. The judge decides on the law and oversees the proceedings, while witnesses provide testimony about the facts. Mixing these roles would create an unfair situation and raise serious doubts about the trial's fairness.

If this situation ever came up, a lawyer would not need to speak up in the moment to object. The problem is considered so obvious and serious that it protects itself automatically. This means the issue can still be raised later, even on appeal, without someone having objected during the trial.