"NEMO JUDEX IN CAUSA SUA"

This is a Latin phrase that means  "a man may not be a judge in his own cause." A judge who is handling a case should not have interest or be connected whether remotely or otherwise with the case before him.
A judge may be disqualified from adjudicating on a matter because he has an interest on that matter, for instance a wife can not preside over a matter affecting her husband, so as to eliminate all traces of the likelihood of BIAS.
Further, because we practice the adversarial system of trial in Nigeria, meaning a system where two opposing parties or adversary, fight in court to win their legal battle, the trial is presided over by an independent and impartial umpire, and conducted according to the rules of evidence and procedure. Therefore, a judge is expected to be a fair and unbiased umpire, by not jumping into the ARENA.
As Dr Johnson said: "God himself, sir, does not propose to judge man until the end of his days." why should you and I?."

Garba v University of Maiduguri
Reference to: Criminal Litigation in Nigeria by A.F Afolayan.
Dr Johnson's quote was found in How to Win Friends and Influence People by Dale Carnegie.