The Doctrine of Precedent & Stare Decisis in Irish Law

Why this is examined

Precedent is the engine of the common law: it explains how a decision in one dispute becomes a rule binding everybody else. It also rests on a tension, which is what makes it examinable — rigid adherence delivers certainty but risks freezing bad law in place, while complete freedom destroys predictability. Irish law balances the two by treating vertical precedent as a binding rule and horizontal precedent as a policy that may be departed from for good reason.

What actually binds: ratio and obiter

Only part of a judgment binds later courts: the ratio decidendi — the reason for deciding — meaning the material facts plus the decision on them. Everything else is obiter dictum — a saying by the way — persuasive, but not binding.

Extracting the ratio is harder than students expect, and the difficulty is not a failure of technique. There is no mechanical test; judges do not label their own ratio, and identifying it is learned by practice rather than by rule. In a multi-judge court — a Divisional High Court, or the collegiate Court of Appeal and Supreme Court — the ratio may have to be distilled from three, five or seven separate judgments, one method being to find the common denominator the judges agreed was essential.

Two refinements catch people out. Where a judge gives two reasons for the decision, both are binding: Behrens v Bertram Mills Circus [1957] 2 QB 1 Persuasive (Eng) shows a later court cannot pick the reason it prefers and treat the other as surplus. And obiter is not worthless — considered judicial dicta, reasoned pronouncements tied to the case, carry real weight, and a considered remark can be adopted as the ratio of a later case. Norris v Attorney General [1984] IR 36 Binding (IE) is the standard illustration of the plainly obiter remark: observations on a subject that was not the issue the court decided.

Vertical precedent: who binds whom

Vertical stare decisis — the obligation to follow the ratio of a superior court — is a binding, non-negotiable rule running strictly down the hierarchy. With the District and Circuit Courts at the base, the Circuit Court must follow the ratio of the High Court, Court of Appeal and Supreme Court; the High Court must follow the Court of Appeal and Supreme Court.

Direction matters as much as level: a High Court decision binds the Circuit Court, yet is only persuasive once the point reaches the Supreme Court. And a lower court stays bound even where the superior court has hinted its own decision may be wrong — the High Court applies a doubted Supreme Court judgment and waits for that Court to overrule itself, because a lower court cannot correct a higher one.

Horizontal precedent: a court and its own decisions

Horizontal stare decisis asks whether a court is bound by its own previous decisions. In Ireland that is a matter of policy, not an unalterable rule — a court generally follows itself, but may depart in a properly exceptional case.

The foundation is The State (Quinn) v Ryan [1965] IR 70 Binding (IE), where the Supreme Court held it is not absolutely bound by its own decisions: the Court treated stare decisis as a policy rather than an unalterable rule. The Court is not the successor of the House of Lords, so it does not inherit the old English rule that a final court is absolutely bound by itself; and because Article 34.3.3° expressly makes one class of decision absolutely binding, it does not follow that every Supreme Court decision is.

Freedom to depart is not willingness to. Attorney General v Ryan's Car Hire [1965] IR 642 set the direction: the Court departs where there is a compelling reason and the earlier decision appears clearly wrong. Mogul of Ireland v Tipperary (North Riding) County Council [1976] IR 260 Binding (IE) fixed the threshold, and its terms matter: it is not enough that the later court would prefer a different conclusion; the Court must be clearly of opinion that the earlier decision was erroneous, and must weigh whether it has become inveterate or the basis of a settled understanding of the law.

That bar was cleared in The People (DPP) v JC [2017] 1 IR 417, applying the Mogul threshold to overrule The People (DPP) v Kenny [1990] 2 IR 110 as wrong in principle. The threshold is applied with particular caution in constitutional matters: precedent still carries real weight where a constitutional question is at stake, so the presence of a constitutional right does not by itself free a court from an earlier decision.

The High Court is in a similar position: it follows its own decisions unless they are manifestly wrong, and in Irish Trust Bank v Central Bank of Ireland [1976–77] ILRM 50 Parke J called such departures extremely rare. A later High Court judge meeting a conflicting High Court decision therefore does not choose freely between them; the earlier decision is followed unless it is manifestly wrong.

Escaping a precedent

Several distinct mechanisms loosen a precedent's grip, and confusing them loses marks:

• Distinguishing — a later court at any level finds the material facts or the legal issue meaningfully different, so the precedent does not apply. This is the one escape genuinely open to a lower court.
• Overruling — a superior court, or a court departing from itself, declares an earlier decision wrong so it is not followed in future. It operates on the law, for later cases.
• Reversing — an appellate court reaches a different result in the very same case on appeal, changing this litigation's outcome rather than the law.

A decision may also never bind, or cease to bind, because of a defect in how it was reached. The chief example is per incuriam — decided through lack of care, in ignorance of relevant law. In Brown v Donegal County Council [1980] IR 132 Binding (IE) the Supreme Court refused to follow one of its own earlier decisions because it had been reached in ignorance of section 685 of the Merchant Shipping Act 1894. The limit is strict: per incuriam runs downwards and sideways only, so a court cannot brand a superior court's decision careless in order to avoid it (Cassell & Co v Broome [1972] AC 1027 Persuasive (Eng)). Precedent also falls away where the ratio has been abrogated by legislation, or where the point was conceded and so never argued.

Persuasive authority, and the one source that binds

Persuasive authority covers decisions of lower courts, obiter dicta, and decisions of other jurisdictions. The Irish courts are not bound by foreign decisions however eminent the court: they are weighed, and often followed, but never compel. The qualification is EU law — relevant rulings of the Court of Justice of the European Union on questions of EU law do bind.

Related free notes: the courts of Ireland · EU law in the Irish legal order · solicitor vs barrister · statutory interpretation · all free Irish Legal System notes.