Case law

Case law, also used interchangeably with common law, is a law that is based on precedents, that is the judicial decisions from previous cases, rather than law based on constitutions, statutes, or regulations. Case law uses the detailed facts of a legal case that have been resolved by courts or similar tribunals. These past decisions are called "case law", or precedent. Stare decisis—a Latin phrase meaning "let the decision stand"—is the principle by which judges are bound to such past decisions, drawing on established judicial authority to formulate their positions.

These judicial interpretations are distinguished from statutory law, which are codes enacted by legislative bodies, and regulatory law, which are established by executive agencies based on statutes. In some jurisdictions, case law can be applied to ongoing adjudication; for example, criminal proceedings or family law.

In common law countries (including the United Kingdom, United States, Canada, Australia, New Zealand, South Africa, Singapore, Ireland, India, Pakistan, Bangladesh, Sri Lanka, Nepal, Bhutan, Israel and Hong Kong), it is used for judicial decisions of selected appellate courts, courts of first instance, agency tribunals, and other bodies discharging adjudicatory functions.

In the common law tradition, courts decide the law applicable to a case by interpreting statutes and applying precedents which record how and why prior cases have been decided. Unlike most civil law systems, common law systems follow the doctrine of stare decisis, by which most courts are bound by their own previous decisions in similar cases. According to stare decisis, all lower courts should make decisions consistent with the previous decisions of higher courts. For example, in England, the High Court and the Court of Appeals are each bound by their own previous decisions, however, since the Practice Statement 1966 the Supreme Court of the United Kingdom can deviate from its earlier decisions, although in practice it rarely does. A notable example of when the court has overturned its precedent is the case of R v Jogee, where the Supreme Court of the United Kingdom ruled that it and the other courts of England and Wales had misapplied the law for nearly 30 years.

Generally speaking, higher courts do not have direct oversight over the lower courts of record, in that they cannot reach out on their initiative (sua sponte) at any time to overrule judgments of the lower courts. Normally, the burden rests with litigants to appeal rulings (including those in clear violation of established case law) to the higher courts. If a judge acts against precedent, and the case is not appealed, the decision will stand.

A lower court may not rule against a binding precedent, even if it feels that it is unjust; it may only express the hope that a higher court or the legislature will reform the rule in question. If the court believes that developments or trends in legal reasoning render the precedent unhelpful, and wishes to evade it and help the law evolve, it may either hold that the precedent is inconsistent with subsequent authority, or that it should be distinguished by some material difference between the facts of the cases; some jurisdictions allow for a judge to recommend that an appeal be carried out. If that judgment goes to appeal, the appellate court will have the opportunity to review both the precedent and the case under appeal, perhaps overruling the previous case law by setting a new precedent of higher authority. This may happen several times as the case works its way through successive appeals. Lord Denning, first of the High Court of Justice, later of the Court of Appeal, provided a famous example of this evolutionary process in his development of the concept of estoppel starting in the High Trees case.

The different roles of case law in civil and common law traditions create differences in the way that courts render decisions. Common law courts generally explain in detail the legal rationale behind their decisions, with citations of both legislation and previous relevant judgments, and often interpret the wider legal principles. The necessary analysis (called ratio decidendi), then constitutes a precedent binding on other courts; further analyses not strictly necessary to the determination of the current case are called obiter dicta, which constitute persuasive authority but are not technically binding. By contrast, decisions in civil law jurisdictions are generally shorter, referring only to statutes.

The reason for this difference is that these civil law jurisdictions adhere to a tradition that the reader should be able to deduce the logic from the decision and the statutes.