This page explains some important legal principles including ratio decendi, obiter dictum, binding vs. persuasive decisions, overruling and distinguishing cases, and the difference between a civil law system and a common law system.
Ratio Decendi/Obiter Dictum
The Ratio decendi is the reason or ground upon which a case is decided. It is the key element of the doctrine of precedent, that is, stare rationibus decidendis, which means ‘let the decision stand’. Sir Rupert Cross defines the ratio as being;
“…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”.
The ratio can be either very wide or very narrow. For example, in Donaghue v Stevenson 1932, it’s said the narrow ratio is;
“a manufacturer owes a duty to take reasonable care that the consumer isn’t injured by defective products”.
The wide ratio is said to be;
“a person owes a duty to take reasonable care that he doesn’t commit any act which he could reasonably foresee as injuring another person”.
The first ratio is narrow because it only applies to manufacturers of products for consumption, whereas the second ratio applies to the whole world and is therefore very wide.
Courts are bound to follow the ratio decendi of other courts whose decisions are binding. The doctrine of precedent creates certainty and consistency in the legal system.
Obiter dictum is a statement of a Judge on a point not needed for the decision to the case he is passing judgement on. An example of this would be if the judge discusses what his decision would have been, had the facts of the case been different, such as in Re Abdul Manan 1971 2 All ER 1016.
The difference between the two is that in the judgement of a case the ratio is a proposition of law that is binding, whereas the dictum is a statement which isn’t necessary for the decision of the case and isn’t legally binding, although can be persuasive, particularly when made in higher courts.
A decision is binding on a later case when;
- the facts of the case are sufficiently similar
- the decision forms part of the ratio decideni
- the Court who made the decision binds the Court the later case is been heard in.
The House of Lords is the supreme court in the English legal system and binds all courts below itself in the hierarchy, and will usually follow its own decisions. The Court of Appeal binds itself and courts below it [Young v Bristol Aeroplane Co Ltd 1944 KB 718], and the High Court binds courts below but not itself. Other courts do not bind themselves or courts below, but previous decisions may be persuasive. The ECJ binds all courts in the UK on matters relating to EC Law or institutions although rulings of other European courts do not.
If a court isn’t bound by precedent, it could be persuaded by any authority, for example, points made obiter dicta or the rulings of lower courts in the hierarchy. An example of this is Combe v. Combe  2 KB 215 where the Court of Appeal was persuaded by an earlier case decided in the High Court [Central London Property Trust Ltd v. High Trees House Ltd  KB 130].
Overruling describes the process where a principle laid down by a lower court in the hierarchy is overturned by a higher court in a different, later case. An example of this is in the case of Hedley Byrne & Co Ltd v Heller & Partners Ltd 1964 AC 465, HL, where the House of Lords overruled the decision made by the Court of Appeal in Candler v Crane, Christmas & Co 1951 2 KB 164, CA, on the point of negligent misstatements.
Judges follow the decisions of sufficiently similar cases but a judge may choose not to follow a precedent, or “distinguish” the cases, where the decision is too obscure, too wide or “not on all fours” with the current case. Alternatively, a judge may decide the ratio of the earlier case is too wide, and therefore should be narrowed and isn’t relevant to the present case.
To compare overruling to distinguishing, overruling is available only to courts higher in the hierarchy to the court where the decision was made, where as any court may distinguish between cases. Overruling will in effect destroy an earlier principal and replace it with a new one, whereas where cases are distinguished, the decision of the earlier case isn’t destroyed – it’s just held not to apply to the particular set of facts in the later case.
Civil Law System/Common Law System
Civil law when contrasted with common law means Roman Law. This is a law system based largely on written codes (with exceptions, such as Scotland who have a civil law system that isn’t based on written codes), which form general principles and are subsequently interpreted by the Courts purposively. There’s no doctrine of precedent but, like in the ECJ, previous decisions are persuasive. The system is the foundation of the law of the majority of member states of the European Union.
Common law in contrast is based on the original English Legal System which was administered in the Common Law Courts and, rather than being a written law, was largely embodied in judicial decisions and custom. Unlike the civil system, there’s a doctrine of precedent, and decisions in earlier cases can bind later cases.