← The hardest concepts in United Kingdom law
In one breath
A court must follow the legal reasoning that was necessary to decide an earlier case in a higher court and, with some exceptions, in its own court. That binding part is the ratio decidendi, and everything else the judges said along the way is obiter dicta, which may persuade but does not bind.
The picture
The recipe and the cook’s chat
Imagine a cookery book in which every recipe comes wrapped in the cook’s chatter: a story about her grandmother, a tip about other dishes, a guess about what might work with fish. If you want to bake the same cake, you follow the quantities and steps that produced it. The story did not make the cake rise, and you need not copy it, though a wise baker may take the fish tip seriously.
A judgment is built the same way. The ratio decidendi is the legal reasoning without which the court could not have reached its result on the facts it found. Obiter dicta are remarks that went further, such as comments on facts that were not before the court. Courts higher in the hierarchy bind those below them. The Supreme Court binds every lower court and may depart from its own earlier decisions when it appears right to do so, which it does rarely. The Court of Appeal is bound by its own earlier decisions, with a few recognised exceptions.
Where the picture stops working
A cook can copy a recipe exactly, whereas a judgment does not label its ratio, and later judges often disagree about what it was. A later court can also distinguish a case on its facts and so narrow it, which a baker copying quantities never does. Scottish courts follow precedent too, with their own hierarchy; for criminal appeals the High Court of Justiciary is the court of last resort.
How it really works
- 1Place the courts in the hierarchy. A court is bound by the decisions of courts above it in its own system and, with exceptions, by its own earlier decisions.
- 2Find the material facts as the earlier court found them, and the question of law it had to answer to reach its result.
- 3State the ratio: the legal proposition necessary to that result. One traditional check is to ask whether the result would have been different had the proposition been the opposite.
- 4Treat what goes beyond that as obiter. Obiter remarks can be persuasive, especially from a senior judge or a full court, but they bind no one.
- 5Compare your facts with the earlier ones. If they differ in a way that matters to the reasoning, the later court may distinguish the case; if they do not, it must follow a binding precedent even if it disagrees.
Why people get it wrong
- Treating the outcome as the precedent. What binds is the reasoning necessary to the outcome, not the fact that one side won.
- Treating everything in the judgment as binding. Remarks on hypothetical facts, or on points the court did not need to decide, are obiter.
- Expecting every case to have a single clear ratio. Where several judges give different reasons for the same result, finding the ratio is itself an argument.
- Assuming that an old decision has lost its authority. Age alone does not remove it; only a court with power to overrule it, or a statute, can do that.
A worked example
The facts are invented
In the invented case Marlow v Hale, the Court of Appeal held a landlord liable in damages for changing the locks to evict a residential tenant without a court order. The judges said that the landlord had no right to use self-help against someone living in the home. In passing, one judge added that the same would surely be true of a shop tenant, and another wondered what would happen if the tenant were months behind with rent.
Years later, Ravi, a residential tenant, is locked out in the same way. The High Court is bound by Marlow, because the ratio, no self-help eviction of a residential tenant, covers Ravi exactly. Ines, a shop tenant, brings a similar claim. The remark about shop tenants was obiter, so the High Court is free to decide for itself, though it will give the remark real weight because it came from the Court of Appeal.
Try it
A Court of Appeal judge says, in passing, how a different case on different facts would be decided. The remark was not needed to resolve the appeal. How does it affect a later High Court judge?
Landmark authorities
Read the sources themselves; this list is a starting point.
- London Street Tramways Co v London County Council, [1898] AC 375
- Young v Bristol Aeroplane Co, [1944] KB 718
- Practice Statement (Judicial Precedent), [1966] 1 WLR 1234
Where to go next
More hard concepts in United Kingdom law
- Statutory interpretation (Legal method)
- Judicial review and its grounds (Administrative law)
This page is an educational overview. It is not legal advice and not a substitute for the sources: the statute, the rule, the case itself. The United Kingdom has three legal systems: England and Wales, Scotland, and Northern Ireland. These pages mostly describe the law of England and Wales and say where Scots law differs when it clearly does; Northern Ireland law is often similar to English law but is not covered separately. Parliament is sovereign, but the devolved legislatures also make law within their powers. Each page states the usual formulation of the rule and names landmark decisions; check the primary sources before relying on any rule.