Ratio Decidendi
The legal reasoning or principle upon which a court's decision is based. The ratio is the binding part of a judgment under the doctrine of precedent.
Independent editorial summary — not the official statute text. Read the official version on legislation.gov.uk.
The ratio decidendi is the rule or principle that explains, and is essential to, a court's decision — as distinct from the result or order itself. In his 2024 Lord Toulson Memorial Lecture at the Supreme Court, Lord Burrows described learning as a law student that it is the ratio decidendi of a case that is binding under the doctrine of precedent, and that there is a distinction between the ratio decidendi and obiter dicta in a judgment.
Lord Burrows went on to explain that, whatever the literal Latin meaning, the ratio decidendi of a case is a term of art and is best understood as being the decision in the case — not primarily the result or outcome for the parties, but the rule or principle explaining that result. Identifying the ratio can require judgement, particularly where a case attracts more than one possible formulation of the underlying principle, or where several judges give differently reasoned judgments reaching the same result.
Related terms
Official sources
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