Precedent · Stare decisis

Ratio decidendi and obiter dicta

Not everything a judge says is binding. The ratio decidendi of a case binds lower courts; obiter dicta do not, although some carry great weight. Telling them apart is the basic skill of reading precedent.

Last updated 9 November 2026

In short

  • Ratio decidendi ("the reason for the decision"): the legal reasoning necessary to decide the case on its material facts. It binds lower courts in the same hierarchy.
  • Obiter dicta ("things said by the way"): statements not necessary to the decision. They are not binding, but may be persuasive.
  • Intermediate appellate courts and trial judges should not depart from seriously considered dicta of a majority of the High Court: Farah Constructions Pty Ltd v Say-Dee Pty Ltd [2007] HCA 22.

What is the ratio decidendi?

The ratio is the principle of law the court applied to the material facts to reach its decision. It is found by identifying the facts the court treated as material, the question the court had to answer, and the reasoning that was necessary to answer it. It is not simply the words a judge chose; later courts often restate a ratio more precisely than the judgment did.

Under the doctrine of precedent (stare decisis), the ratio of a decision binds courts lower in the same hierarchy. Decisions of the High Court bind every Australian court.

What are obiter dicta?

  • Statements of law on questions the court did not need to decide.
  • Remarks on hypothetical facts, or on how the case would have been decided on different facts.
  • Reasoning in a dissenting judgment.
  • Observations on a question the court expressly left undecided. (Where a court decides a case on two independently sufficient grounds, both can form part of the ratio.)

Obiter is not binding, but its weight depends on the court and on how carefully the point was considered. A considered statement of the High Court can be more influential than the ratio of a lower court.

Seriously considered dicta of the High Court

In Farah Constructions Pty Ltd v Say-Dee Pty Ltd [2007] HCA 22; (2007) 230 CLR 89 the High Court said that intermediate appellate courts and trial judges should not depart from seriously considered dicta of a majority of the High Court. The same decision said that intermediate appellate courts and trial judges should not depart from a decision of an intermediate appellate court in another jurisdiction on the interpretation of Commonwealth legislation or uniform national legislation unless convinced it is plainly wrong, and that the same applies to the common law, because there is one common law of Australia.

Read it in the case index: Farah Constructions v Say-Dee [2007] HCA 22.

Finding the ratio when there are several judgments

Appellate courts often deliver separate judgments. A binding ratio exists only where a majority of the judges agree on the reasoning necessary for the result. Where the majority reach the same result by different reasoning, the High Court has said that the decision may bind only as to its result on materially indistinguishable facts: see Federal Commissioner of Taxation v St Helens Farm (ACT) Pty Ltd (1981) 146 CLR 336.

  1. Identify the orders, and which judges joined in them.
  2. For each majority judge, state the reasoning necessary to their conclusion.
  3. Find the reasoning common to a majority. That is the ratio, if there is one.
  4. Treat everything else, including dissents, as obiter.

Frequently asked questions

What is the difference between ratio decidendi and obiter dicta?

The ratio decidendi is the reasoning necessary to decide the case and binds lower courts. Obiter dicta are remarks not necessary to the decision; they do not bind, but can be persuasive.

Is obiter dicta binding in Australia?

No, but lower courts should follow seriously considered dicta of a majority of the High Court, per Farah Constructions v Say-Dee.

Is a dissenting judgment obiter?

Yes. A dissent is not part of the ratio, though its reasoning can later be adopted by a majority in another case.

Sources

General information, not legal advice. See our editorial policy for how this page is sourced and reviewed, and how to report an error.

Read the authorities, not a summary of a summary

Barrister AI links each principle to the judgments that apply it, with pinpoint citations you can check paragraph by paragraph.

Start free