5.3 Nemo Judex in Causa Sua (the Rule against Bias)

The rule: no one may judge a cause in which they have an interest — the decision-maker's impartiality as the decision's validity condition. The bias's forms: Pecuniary bias: the decision-maker's financial interest in the outcome — automatic voidness, however small the interest (the historic rule); Personal bias: the relationship (kinship, friendship) or the enmity with a party; Subject-matter bias: the decision-maker's own policy or prior conduct embedded in the dispute — the department judging its own case; Institutional/departmental bias: the combined functions — the prosecutor and the judge fused in one office (the structural unfairness). The test's evolution: from the "reasonable suspicion" test (would a reasonable person suspect bias?) to the real danger test (would a fair-minded and informed observer, viewing the facts, conclude there was a real danger of bias?) — the modern standard, balancing the administration's workability against fairness's rigour. The rule's edges: the bias's waiver (the party knowing and not objecting); the multi-member body's partial taint (one biased member among a well-constituted bench — the case-by-case answer); the same-hearing-same-decision requirement (the one who hears must decide — the report's adoption problems).