Stare decisis [Latin, "let the decision stand"] refers to the doctrine of precedent, according to which the rules formulated by judges in earlier decisions are to be similarly applied in later cases. The reason for the doctrine is that similar cases should be treated alike so as to ensure consistency and certainty in the law. It evolved in the primarily "judge-made" COMMON LAW system of the law and attained its most formal expression in late 19th-century England.
In practice today the doctrine means only that prior decisions of higher courts are binding on lower courts of the same jurisdiction, for neither the Supreme Court of Canada nor many of the provincial courts of appeal consider themselves bound by their own previous decisions. Lower courts are also free to analyse the reasons (ratio decidendi) given by the higher court and to decide, in light of the facts of the actual dispute before them, whether to apply the precedent or to distinguish the rule contained on the basis of factual differences in the 2 cases. The doctrine, within these same limits, also applies in the interpretation of statutes. Its role in Québec civil law is of less importance and is a matter of debate.