Should a judge in a criminal trial have credibility?

The word "credibility," while not exactly a legal term of art, in the law generally is used to characterize a witness whom the jury believes. When we say a witness has credibility, we mean the witness presents in a way that makes people think the witness is telling the truth. That particular use of the word does not seem applicable as applied to a judge. If we use the word in a larger sense, I would say a judge should have credibility in a criminal trial — or a civil trial, for that matter. 

A judge needs to be credible in his or her capacity as a judge. If we see a judge who is fumbling over legal concepts to make clearly erroneous rulings, who mispronounces words and has poor grammar, or who demonstrates clear partiality to one side or another, we are looking at someone who is not credible as a judge. A judge whose demeanor suggests that the proceedings are a joke or a waste of time does not have credibility as a judge. A judge caught sleeping on the bench loses all credibility. 

A judge's credibility matters a great deal in a country that functions under a rule of law. The judge is an integral part of the legal process, the person we count on to take the proceedings seriously, to guard the rights of the prosecution, the defendant, and the people, to understand the law, to be impartial, and to have a demeanor proper for the situation. If a judge has no credibility, we lose respect for the process, and when people lose respect for the process, it makes them less likely to be willing to live under the rule of law.

There are not enough people available to enforce a rule of law if large numbers of people are no longer willing to consent to be ruled by law. What would constitute a critical mass in this context is unclear, but there is a tipping point after which could come revolution or anarchy.  A failure to believe in government institutions has been responsible for many revolutions, and not just historically; even today, the Egyptian Spring and the civil war in Syria began because citizens doubted their governments. 

The judiciary is a government institution. It must command the respect of the people or fail. One way that respect is commanded is by ensuring there are judges with credibility.  In some states, judges are elected. In others, they are appointed. Either way, judicial candidates are carefully vetted by a state bar association. At the federal level, judges are appointed by the president, and these judges, too, are carefully vetted. Most of the time, people who would not make credible judges do not become judges.