From IVR encyclopedie
by Roger Shiner
The ratio decidendi of a case is the ground or reason the case is decided in the way that it is decided. Theratio decidendi is the aspect of a case that determines or is dispositive for the decision in the case. Although the above characterization is expressed in very general terms, such that it could cover any source for the legal materials deployed in judicial decision-making, in practice the term ratio decidendi is in practice associated solely with decisions based on precedent in common law adjudication. [See entry on PRECEDENT.] In fact, the chief device for managing issues of relevance in the area of common law precedent is the notion of ratio decidendi. The reasons for its importance are two. Take first the case of a hierarchy of courts. Imagine a judge lower in a hierarchy who is, according to the rules of the hierarchy, bound by decisions of a higher court on the matter at issue. How is such a judge to know whether there are or are not decisions of a higher court on the issue before him or her? The short answer is: if an issue before a judge in a lower court comes within the scope of a ratio decidendi of a decision of a higher court, then the judge of the lower court is bound to apply such a ratio to the case before him or her. Take second the case of a court at the appellate level, and consider the relationship of that court to its own previous decisions. How is the court to know whether it has already decided in a previous case the issue presently before it? Again, the short answer is: if an issue presently before a court comes within the scope of a ratio decidendi of a previous decision of that court. How important such a determination is will depend on the decision-making rules in force in a given jurisdiction. If there is no convention in force that courts are bound by their own previous decisions, then determination of the ratio decidendi of a previous decision is not especially significant. However, in the U.K., in London Tramways v London County Council  AC 375, the House of Lords decided that it should be bound by its own previous decisions, a situation that existed until 1966 when it rescinded that decision. Between 1898 and 1966, therefore, it was crucially important for the House of Lords to be able to identify the ratio decidendiin cases it had previously decided, and thus the proper determination of rationes became a matter for great technicalities. No other jurisdiction has imposed on itself such strict procedural rules with respect to courts’ relations to their own previous decisions as did the U.K. in the period noted.
It is therefore crucially important, from the point of view of understanding theoretically common law reasoning from precedent, that we can identify what it is with respect to some decided case that is the ratio decidendi of the case.
The first point to be made in this project is that the ratio decidendi (whatever it is) is to be distinguished from an obiter dictum. In the course of an official written opinion, a judge or a court will say many things. They will review the agreed facts; they will review applicable legislation; they will review existing decisions; they will review submissions by counsel or by intervenors; they will present patterns of reasoning; they will ultimately render a verdict. Whatever the ratio decidendi is, it will found among all this material. The ratio will typically not be found among the various reviews mentioned above, nor in the verdict itself. It will typically be found in the reasoning presented for the verdict. Even there, however, judges both make remarks that specifically relate to the case in point, and remarks which are of a more general character, about possible implications of the instant case, about the state of the law generally, and so forth. These remarks are known as obiter dicta, expressions of opinion by a judge that are external to the dispositive reasoning in the case. The problem remains, though: how can one distinguish in the reasoning of a judge the part that constitutes theratio decidendi and the part that constitutes obiter dicta? The issue of what exactly it is that constitutes theratio of a case is one that has been hugely debated by theorists of the common law. The debate is charted, and the different theories evaluated, most thoroughly by Cross and Harris (Cross and Harris 1991, 39–96). Complex though the debate is, there are fixed points of reference.
a) Judges will frequently say what they take to be the point of law at issue in a case. But even so the ratio decidendi cannot be equated to any such statement. The words the judge uses do not have canonical force, unlike the words of a statute. In a case governed by statute, a court faced with a situation in which the application of the statute is unclear cannot disregard the wording of statute. They must instead seek to interpret the wording of the statute, and discern its applicability by such a process. In the case of a statedratio, a later court is under no analogous obligation. It can legitimately state the ratio of the precedent case in different words than the judge(s) hearing the precedent case themselves used.
b) Moreover, it is simply not possible for a judge to create a legal norm simply by saying they are doing such a thing. The ratio decidendi in a case must have some internal relationship both to the actual facts of the instant case and to judgments that have been made in other cases. Also, the established semantics and syntax of natural language exercise influence (Stone 1968, 36).
c) The ratio cannot be equated with the actual reasoning given by a judge in favour of his or her decision, as that reasoning may be poor or worse from the point of view of legal science. Likewise, the ratio cannot be equated with any actual putative rule set forth by a judge, since it may be either broader or narrower than any such putative rule.
d) Despite the fact that the language of `rule’ is standardly used as a characterization of the ratio decidendi, it can be misleading to describe the ratio of a case as a `rule’. Neil MacCormick has argued that a ratio is more properly speaking a `ruling’ (MacCormick 1987, 179). An interpretation of a statute given in a case may come to be a precedent for future interpretations; but it is not the `rule’ in the case, the statute is. Moreover (and I will return to this later), it is frequently only clear after a series of future decisions that a precedent case stands for a given ratio. Once such a hardening process has taken place, then talk of the `rule’ in the original precedent case becomes appropriate. For all that, the case will have had a ratio at the time. Of course, if one thinks, as some do, that even the ratio of a case is subject to determination by later courts, then this proffered distinction between `rule’ and `ratio’ becomes much harder to make.
The two most plausible theories are those of A.L. Goodhart, and of Cross and Harris themselves. Goodhart has famously suggested that the ratio decidendi of a case is constituted by the principle that derives from thematerial facts of the case (Goodhart 1931, 1–36), or, more precisely, the facts that the judge treats as material facts in relation to the judgment the judge issues. He is careful to note that facts may be treated as materially either implicitly or explicitly. Goodhart is right to point out that, in the total fact situation of any actual case, some facts will matter from the legal point of view and some will not. That the accused was seen driving away from the bank at high speed moments after the robbery matters; that the accused was driving a Ford does not; unless matter of identification are at issue, in which case it might matter; and so on. Even if one recognizes that there will be some interdependence between the principle for which a case is thought to stand, and the facts of the case thought to be material, the advantage of Goodhart’s approach — to have the concept of `material fact’ drive the concept of ratio — is that it makes easier the preservation of the non-canonical character of the language of a common law legal opinion. One important reason in favour of Goodhart’s view is that the material facts are usually relatively easy to determine, and they will not change as time goes by. The objection to his view is that the ratio is typically broader in scope than any recitation of material facts. In the famous case of Donoghue v Stevenson  AC 567 (HL), the material facts concerned a decomposed snail in a ginger beer bottle, but unquestionably the ratio decidendi of the case was some broader principle concerning the liability of manufacturers for harm occurring to ultimate consumers. The same case shows even the concept of `fact’ to have some fuzziness. The case went to the House of Lords on the basis that, if the facts were as the plaintiff alleged, did the defendant have a case in law to answer? The `material facts’ that produced such a substantial change in the common law of negligence were in reality `alleged material facts’. It is a matter for further contemplation whether the `material fact’ view can be emended to deal with these concerns.
Cross and Harris propose the following understanding of ratio decidendi: `The ratio decidendi of a case is any rule of law expressly or impliedly treated by the judge as a necessary step in reaching his conclusion, having regard to the line of reasoning adopted by him, or a necessary part of his direction to the jury’ (Cross, et al. 1991, 72). Such an account captures many of the fixed points enumerated above, and is therefore an attractive proposal. The difficulty in the proposal is this. Whatever the ratio decidendi of a case is, it is something that is determinative or dispositive. That is, the ratio is not merely necessary but also in some sense sufficient for the decision in the case. It is not clear how Cross’ and Harris’ proposal explains this element of sufficiency.
Cross, R., and J. Harris. 1991. Precedent in English Law. 4th edn. Clarendon Law Series. Oxford: Clarendon Press.
Goodhart, A. 1931. Essays in Jurisprudence and the Common Law. Cambridge: Cambridge University Press.
MacCormick, N. 1987. `Why Cases have Rationes and What These Are’. In Precedent in Law, ed. L. Goldstein, 155–82. Oxford: Clarendon Press.
Stone, J. 1968. Legal System and Lawyers’ Reasonings. Sydney: Maitland Publications Pty. Ltd.