Per Incuriam in UK Law

Where the court has construed a statute or a rule having the force of a statute its decision stands on the same footing as any other decision on a question of law, but where the court is satisfied that an earlier decision was given in ignorance of the terms of a statute or a rule having the force of a statute the position is very different. Such cases would obviously be of the rarest occurrence and must be dealt with in accordance with their special facts.

As a general rule the only cases in which decisions should be held to have been given per incuriam are these of decisions given in ignorance or forgetfulness of some inconsistent statutory provision or of some authority binding on the Court concerned: so that in such cases some part of the decision or some step in the reasoning on which it is based is found, on that account, to be demonstrably wrong.

One of the conclusions reached in the judgment of the Master of the Rolls is that if the Court of Appeal, when sitting in one of its Divisions, has in a previous case pronounced on a point of law which necessarily covers a later case coming before the Court, the previous decision must be followed (unless, of course, it was given per incuriam, or unless the House of Lords has in the meantime decided that the law is otherwise), and that this application of the rules governing the use of precedents binds the full Court of Appeal no less than a division of the Court as usually constituted.

One of these is where a previous decision of this Court, although not expressly over-ruled, cannot stand with a subsequent decision of the House of Lords, see 1944 1 K.B. at page 725. To these I would add that a case is not decided per incuriam because Counsel have not cited all the relevant authorities or referred to this or that rule of Court or statutory provision. The Court does its own researches itself and consults authorities; and these may never receive mention in the judgments.

Having rejected the theory that Lord Devlin's speech can be pushed aside as having been delivered per incuriam, I hope I may now equally dispose of another misconception. I do not think that he was under the impression either that he had completely rationalised the law of exemplary damages, nor by listing the "categories" was he intending, I would think, to add to the number of torts for which exemplary damages can be awarded.

The Court of Appeal found themselves able to disregard the decision of this House in Rookes v. Barnard by applying to it the label per incuriam. That label is relevant only to the right of an appellate court to decline to follow one of its own previous decisions, not to its right to disregard a decision of a higher appellate court or to the right of a Judge of the High Court to disregard a decision of the Court of Appeal.

Like all exceptions to, and modifications of, the strict rule of precedent, this rule must only be applied in the most obvious of cases, and limited with great care. The basis of it is that the proposition in question must have been assumed, and not have been the subject of decision. And there may of course be cases, perhaps many cases, where a point has not been the subject of argument, but scrutiny of the judgment indicates that the court's acceptance of the point went beyond mere assumption.