Procedural impropriety in Singapore administrative law

Procedural impropriety in Singapore administrative law is one of the three broad categories of judicial review, the other two being illegality and irrationality. A public authority commits procedural impropriety if it fails to properly observe either statutory procedural requirements, or common law rules of natural justice and fairness.

The common law rules of natural justice consist of two pillars: impartiality (the rule against bias, or nemo judex in causa sua – "no one should be a judge in his own cause") and fair hearing (the right to be heard, or audi alteram partem – "hear the other side"). The rule against bias divides bias into three categories: actual bias, imputed bias and apparent bias. There are currently two formulations of the test for apparent bias, known as the "real likelihood of bias" test and the "reasonable suspicion of bias" test. Some controversy exists as to whether there is in fact any material difference in the two formulations.

Fair hearings must include sufficient notice to prepare a case, prior knowledge and opportunities to contest, contradict or correct any evidence that will be introduced in the case, and the ability to raise relevant matters before the court. In addition, a fair hearing may also include the rights to legal representation, to cross-examine witnesses, and to be given reasons for a decision; and a presumption in favour of an oral hearing.

The concept of law in provisions of the Constitution of the Republic of Singapore such as Article 9(1) and Article 12(1) includes what are called "fundamental rules of natural justice". According to the Court of Appeal, the content of fundamental rules of natural justice is the same as the common law rules of natural justice, but there is a qualitative difference in how the rules apply. A breach of the former can lead to legislation being struck down on the ground of unconstitutionality. On the other hand, a breach of the latter has the effect of invalidating administrative decisions but cannot affect the validity of legislation.

More recent case law from the UK tends to refer to a duty of public authorities to act fairly rather than to natural justice. One aspect of such a duty is the obligation on authorities in some cases to give effect to procedural legitimate expectations. These are underpinned by the notion that a party that is or will be affected by a decision can expect that he or she will be consulted by the decision-maker before the decision is taken.