nemo judex in causa sua

This is one of the two main rules of natural justice. A decision-maker must not have an interest in the outcome or be biased towards a party. Bias may be pecuniary (any financial interest, however small, disqualifies), personal (relationship, friendship or hostility), or official (prior involvement in the matter, as prosecutor and judge).

The test is whether there is a real likelihood or reasonable apprehension of bias in the mind of a fair-minded observer; actual bias need not be proved, because justice must be seen to be done. The doctrine of necessity is an exception: where no other authority can decide, the biased authority may act.

Example

Because a candidate for selection sat on the selection board, the selection was set aside under nemo judex in causa sua.

In Indian law

• A.K. Kraipak v. Union of India, 1969 INSC 129
• Dimes v. Grand Junction Canal (House of Lords, 1852): pecuniary bias

See also

natural justice · audi alteram partem · reasoned decision

Read more in the study notes

• Classification of administrative action (Administrative Law)
• Judicial power of the administration: quasi-judicial functions and administrative adjudication (Administrative Law)
• The rule against bias (Administrative Law)
• Audi alteram partem: the right to a fair hearing (Administrative Law)
• Reasoned decisions, exceptions to natural justice, effect of breach and Article 136 (Administrative Law)
• Government contracts and state liability: the administrative-law angle (Administrative Law)