Can a judge ever call an expert witness to the bench for a private tete-a-tete? Attorneys argued both sides of that issue before the Pennsylvania state Supreme Court last week in Philadelphia, in a case that could help define the boundaries of a trial judge’s discretionary powers.

In the decision that was appealed, the Superior Court granted the plaintiffs a new trial, finding they were prejudiced when a common pleas court judge asked a defense witness — whom he described as an “old friend” — to engage in a sidebar conversation that allegedly had nothing to do with the trial.