precedent

Precedent is a principle or rule established by a prior court decision that guides future judgments in cases involving similar facts or issues. In common law systems, most rules of law are developed through case law rather than only statutes, making precedent a central mechanism for consistency and predictability.

Stare decisis, Latin for 'to stand by things decided,' is the doctrine that courts should follow binding precedents established by higher courts within the same jurisdiction. The binding effect is strongest for decisions that contain the ratio decidendi—the legal rule or rationale necessary to decide the case. Obiter dicta, remarks made in passing, are generally persuasive but not binding.

Precedent is categorized as binding or persuasive. Binding precedent must be followed by lower courts in similar circumstances; persuasive authority—such as decisions from other jurisdictions or from courts of equal rank—may be considered but is not obligatory.

Legal systems differ in how strongly they rely on precedent. In common law jurisdictions, precedent plays a central and continuing role; in many civil law jurisdictions, statutes and codes take precedence, and the influence of past decisions is more limited, though judicial opinions can guide interpretation and reform.

Precedent can be refined or overturned as society, technology, and policy change. Courts may distinguish a case to avoid applying an unfavorable precedent, overrule an earlier decision, or rely on statutory changes to alter the rule. The use of precedent aims to balance consistency with adaptability in the law.