Nemo iudex in causa sua

Nemo judex in causa sua (or nemo judex in sua causa) (which, in Latin, literally means "no-one is judge in his own cause") is a principle of natural justice that no person can judge a case in which they have an interest. In many jurisdictions 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". This principle may also be called: nemo judex idoneus in propria causa est nemo judex in parte sua nemo judex in re sua nemo debet esse judex in propria causa in propria causa nemo judex 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. The phrase is credited to Sir Edward Coke in the seventeenth century, but has also been attested as early as 1544. It appears in the 1974 United States Supreme Court case of Arnett v. Kennedy ("we might start with a first principle: '[N]o man shall be a judge in his own cause.' Bonham's Case, 8 Co. 114a, 118a, 77 Eng. Rep. 646, 652 (1610)"). In 2022 and 2023 United States Senator Sheldon Whitehouse repeatedly invoked the phrase in the context of discussions about ethics policies of the Supreme Court.