Ratio decidendi and obiter dicta
The ratio decidendi is the legal principle or reasoning that was necessary to the court's decision — it is the binding part of a judgment under the doctrine of precedent. Obiter dicta are remarks “said by the way” that were not essential to the outcome, and are only persuasive.
Last reviewed 14 June 2026
Identifying the ratio means asking which proposition of law the result actually turned on. Everything else — hypothetical examples, comments on points not in issue, dissenting reasoning — is obiter.
Only the ratio binds lower courts under stare decisis. Obiter dicta, especially from senior courts, can still be highly influential: Lord Atkin's wider statement of the neighbour principle in Donoghue v Stevenson began life as reasoning that later courts adopted.
Key cases
- Donoghue v Stevenson [1932] AC 562
Frequently asked questions
What is the difference between ratio decidendi and obiter dicta?
The ratio is the reasoning necessary to the decision and is binding; obiter dicta are incidental remarks that did not decide the case and are only persuasive.
Is obiter dicta binding?
No — obiter is not binding, but it can be persuasive, particularly when it comes from the Supreme Court or Court of Appeal.