The Gra brings up the point that a case brought before a judge might require a decision based on the pleas but the truth might be elsewhere. In such a case he said the judge must remove himself. This occurred to me when learning the Rambam concerning civil cases. The Halacha might require one decision but the judge might be aware that it is  a דין מרומה. There is something under the surface that is not being presented. See Shir Hashirim on the verse הנה מטתו של שלמה.
If the judge decides like the truth against the law of the Torah then there is the sword on his neck. If he decides like the law of the Torah against the real truth then Hell opens up beneath him.