Bias: reasonable apprehension of impartiality bars decisions when circumstances create a real likelihood of prejudice. The doctrine of bias invalidates action where there is a reasonable possibility that a decision maker is predisposed against a party. Three forms-subject matter, pecuniary and personal-are recognised; courts apply a fact sensitive test of real likelihood or reasonable apprehension evaluated from the viewpoint of a reasonable informed person, requiring cogent positive evidence rather than conjecture.