Nemo iudex in causa sua

Nemo iudex in causa sua (or nemo iudex in sua causa) is a Latin phrase that means, literally, no-one should be a judge in their own cause. It is a principle of natural justice that no person can judge a case in which they have an interest. The rule is very strictly applied to any appearance of a possible bias, even if there is actually none: "Justice must not only be done, but must be seen to be done".

May also be called:

• nemo iudex idoneus in propria causa est
• nemo iudex in parte sua
• nemo debet esse iudex in propria causa
• in propria causa nemo iudex

The other principle of natural justice is "Hear the other party" (Audi alteram partem or "The right to hearing") otherwise put "Reasonable opportunity must be given to each party, to present his side of the case".

The legal effect of a breach of natural justice is normally to stop the proceedings and render any judgment invalid; it should be quashed or appealed, but may be remitted for a valid re-hearing.

See also

• List of legal Latin terms