Nemo judex in sua causa – this legal phrase comes From Latin. It refers towards a major legal principle which states that no person can judge a case in which he or she participates as a party (i.e. pursues personal benefits). In brief words it means that nobody can judge on their own lawsuit, otherwise there would be no fair justice. In the legal practice, magistrates (judges and prosecutors) are to be withdrawn from lawsuits in which they have personal interest. For example, a judge cannot hear and decide on lawsuit for damages if he/she is the injured claimant who lodged the tort claim, or a close member of their family – because the judge is considered personally interested in the award and the outcome of the court case.

Any court decision, taken against the provision of this legal doctrine, should be voided and proclaimed invalid; and the lawsuit – re-heard by another, non-interested magistrate. This rule also applies in situations where the judge on a lawsuit is a witness of events within the subject of the case. The goal of the Law is to secure delivering fair justice.

An exclusion of this principle is the “rule in necessity”, which applies in rare and extraordinary situations to entitle a judge to hear lawsuits although there may be a conflict of interests.

Synonyms are the terms “Nemo judex in parte sua” and “Nemo debet esse judex in propria causa”.