What does ALIQUIS NON DEBET ESSE JUDEX IN PROPRIA CAUSA, QUIA NON POTEST ESSE JUDEX ET PARS mean?

ALIQUIS NON DEBET ESSE JUDEX IN PROPRIA CAUSA, QUIA NON POTEST ESSE JUDEX ET PARS meaning in Law Dictionary

person ought never to be judge in his own cause, because he cannot act as judge and party. Co. Litt. 141; 3 Bl. Comm. 59.