Nemo debet esse judex in propria sua causa, that, is, no man can be a judge in his own cause.
Judges and Magistrates have a disqualification if they have an interest in the matter or if he is a party to the matter.
Pecuniary interest, if it is a direct interest without regard to its quantum, is a disqualification and so is any other interest if it is substantial to create a reasonable apprehension of bias. Section 555 of the Code of Criminal Procedure lays down that no Magistrate except with the leave of the court to which an appeal lies from his Court shall try any case to which he is a party or has a personal interest. No Magistrate can try a case in which he himself is a witness. A conviction by bench of magistrates of which he was member is liable to be quashed.
Section 556, (old) 479 (new), Criminal Procedure Code, which embodies the maxim nemo debet esse judex in propria sua causa (no man can be a judge in his own case) does not apply to summary proceedings taken for punishing contempt. The gravamen of the charge of contempt is an endeavor to shake the confidence of the public in the court and not to protect the individual judges of the court. The court, in such cases does not seek to vindicate any personal interest of the judges, but the general administration of justice, which is a public concern.
In a case in which a judge has been personally attacked, it is his duty to sit in judgment as it is impossible to vindicate the reputation of the court which has been attacked by taking proceedings in any other court for libel or otherwise. [In re, K.L. Gauba, barrister-at-Law, Lahore, 1942 Lah 105 : 43 CrLJ 599; In re, Motilal Ghose, 45 Cal 169 : 45 IC 388 :21 CWN 1161; In re, Murli Mahohar Prasad, 8 Pat 323; In the matter of William Tylor, 1918 Cal 713; R. v. Davies, (1906) 1 KB 32 (40)]. [Contempt of Courts Act]