When making decisions, all relevant considerations need to be taken into account and irrelevant considerations should be ignored. Crucially, when it actually comes to the decision, it must not be so unreasonable that no reasonable person acting properly could have taken it. These are often called the ‘Wednesbury principles’ after the name of the court case which first established them.
The test of unreasonableness concerns the decision as well as the way in which it was reached. Even if the decision-maker has taken into account the correct considerations, they may still come to a decision so wildly unreasonable or perverse that it can be judged to have been outwith the decision-maker’s discretion to make it. If this happens then the decision will be unlawful.
The court has recognised that when different reasonable people are given the same set of facts, it is perfectly possible for them to come to different conclusions. This means a range of lawful decisions may be within the discretion of the decision-maker. However, at the same time, the court has defined a category of decisions which lie outside that range of discretion. These have been described as:
- ‘a decision which is so outrageous in its defiance of logic or accepted moral standards that no sensible person who had applied his mind to the question could have arrived at it’
- ‘beyond the range of responses open to a reasonable decision-maker’.
If a decision is challenged, the court or tribunal will examine it to see whether it was made according to logical principles, and will often expressly state that it is not its intention to substitute its own decision for that of the decision-maker. The court will not make its own decision in place of that of the decision-maker because it bears in mind that the legislation has given the discretion to make the decision to a particular decision-maker, and it is not for the court to make that decision instead.