Legal Method: Ratio Decidendi vs Obiter Dicta

The doctrine of precedent (stare decisis) means courts follow earlier decisions. But not every word of a judgment binds later courts. Only the ratio decidendi is binding; everything else is obiter dicta, which is merely persuasive. Telling them apart is a core legal skill.

What Is the Ratio Decidendi?

The ratio decidendi is the legal principle that was necessary to the decision on the facts. It is the reasoning without which the court could not have reached its result. A later court at the same or lower level is bound by it.

What Is Obiter Dicta?

Obiter dicta are things said by the way: comments not necessary to the decision. Examples include observations on hypothetical facts, discussion of how the law might apply in a different case, and the reasoning of a dissenting judge. Obiter can be highly persuasive, especially from a senior court, but it does not bind.

How to Find the Ratio

Step 1: Identify the material facts

The ratio is tied to the facts the court treated as material. Strip the decision back to those facts.

Step 2: Find the rule applied to those facts

Ask what legal proposition the court must have accepted in order to decide as it did. That proposition, at the right level of generality, is the ratio.

Step 3: Test it

If you removed the proposition, would the outcome still stand? If not, it is part of the ratio. If the outcome survives without it, it is obiter.

Why the Distinction Matters

When a later case is materially similar, the earlier ratio binds. When the facts are different, an advocate distinguishes the precedent. Skilful use of obiter, and skilful distinguishing, is how the common law develops without a court having to overrule anything.

Conclusion

Ratio binds, obiter persuades. Train yourself to ask, for every proposition in a judgment, whether the result depended on it. That habit underpins case briefing, essay writing and advocacy alike.