הלכה על שבועות 60:18

From the laws of the commandment is that which they, may their memory be blessed, said (Shevuot 30b) that any judge who knows about a case that it is rigged, that he is obligated to remove himself from it, and not say, "I will conclude it and the chain will be around the neck of the [lying] witnesses"; and the great praises with which the sages praised the seeking of truth and the distancing of falsehood in judgment. And the rest of its many details - are elucidated in Sanhedrin and also in the Midrash (see Mishneh Torah, Laws of The Sanhedrin and the Penalties within their Jurisdiction 25).