Callinan and Heydon JJ recently observed that ‘unfairness can spring not only from a denial of an opportunity to present a case, but from denial of an opportunity to consider it’. They explained that the failure to fairly consider a case could arise ‘not only from obstruction … of its presentation but also from self-disablement by the [decision maker] from giving consideration to that presentation by permitting bias to affect its mind’. Their Honours were right to suggest that the two pillars of natural justice – the hearing rule and the rule against bias – each emanate from notions of fairness, but each fosters fairness in different ways. The hearing rule governs the right to know and be heard. It is the source of principles governing the information that should be provided to a person who may be affected by a potential decision, when the information should be provided and how the person should be able to put his or her views to the decision maker. The bias rule provides an important complementary right, which is to ensure that the decision maker to whom the hearing rule applies is impartial and can approach a decision with an open mind.

This chapter examines the test governing allegations of bias and the apparently objective standard by which a court asks whether a well-informed observer would reasonably apprehend that a decision maker might not bring an impartial mind to a decision.