Among rules of law Karl Llewellyn noted at one extreme the “rule-of-thumb, in which the flat result is articulated, leaving behind and unexpressed all indication of its reason”. At the other extreme was “the way of principle, in which the reason is clearly and effectively articulated, and that articulation is made part of the very rule”. The vice of principle, he observed, “can be a vaporish vagueness, and the techniques of its effective formulation are not easy to isolate for communication and use”. Partly for this reason, partly perhaps because of its origin in a last-minute political compromise, section 78(1) of the Police and Criminal Evidence Act 1984 at first confounded attempts to predict the manner of its application. One commentary suggested that it was “of no practical use”; there were dicta in the Court of Appeal to the effect that it did “no more than to re-state the power which judges had at common law before the Act of 1984 was passed”. A leading work on the law of evidence expressed the view that the sub-section was “cast in terms of such vagueness and generality as to furnish little guidance to the court”. There has been some development since those early days. It now seems clear that the Police and Criminal Evidence Act 1984 is to be regarded as a codifying Act which has to be looked at on its own wording. Section 78(1), therefore, does not merely re-state the position at common law. It is also clear that in its operation it overlaps section 76 and, through section 82(3), some of the common law. Section 78(1) may be applied in a variety of situations, with or without the presence of some element of impropriety in the way in which the evidence was obtained. Basic questions about its operation nevertheless remain.
Smith v Chief Constable of Sussex Police; [2008] UKHL; 50
