Stare decisis is a common law doctrine under which judges are obligated to follow the precedents established in prior decisions.
Stare decisis is the policy of the court to stand by precedent; the term is but an abbreviation of stare decisis et quieta non movere — "to stand by and adhere to decisions and not disturb what is settled." Consider the word "decisis." The word means, literally and legally, the decision. Nor is the doctrine stare dictis; it is not "to stand by or keep to what was said." Nor is the doctrine stare rationibus decidendi — "to keep to the rationes decidendi of past cases." Rather, under the doctrine of stare decisis a case is important only for what it decides — for the "what," not for the "why," and not for the "how." Insofar as precedent is concerned, stare decisis is important only for the decision, for the detailed legal consequence following a detailed set of facts.
In other words, stare decisis applies to the holding of a case, rather than to obiter dicta. As the United States Supreme Court has put it: "dicta may be followed if sufficiently persuasive but are not binding.
The doctrine that holdings have binding precedential value is not valid within most civil law jurisdictions as it is argued that this principle interferes with the right of judges to interpret law and the right of the legislature to make law. Most such systems, however, recognize the concept of jurisprudence constante, which argues that even though judges are independent, they should rule in a predictable and non-chaotic manner. Therefore, judges' right to interpret law does not preclude the adoption of a small number of selected binding case laws.
The idea that a judge is bound by (or at least should respect) decisions of earlier judges of similar or coordinate level is called horizontal stare decisis.
In the United States federal court system, the intermediate appellate courts are divided into "circuits". Each panel of judges on the court of appeals for a circuit is bound to follow the prior appellate decisions of the same circuit. Precedents of a United States court of appeals may be overruled only by the court en banc, that is, a session of all the active appellate judges of the circuit, or by the United States Supreme Court.
When a court binds itself, this application of the doctrine of precedent is sometimes called horizontal stare decisis. The State of New York has a similar appellate structure as it is divided into four appellate departments supervised by the final New York State Court of Appeals. Decisions of one appellate department are not binding upon another, and in some cases the departments differ considerably on basic points of law.
This situation changed, however, after the issuance of the Practice Statement of 1966. It enabled the House of Lords to adapt English law to meet changing social conditions. In R v G & R 2003, the House of Lords overruled its decision in Caldwell 1981, which had allowed the House to establish mens rea ("guilty mind") by measuring a defendant's conduct against that of a "reasonable person," regardless of the defendant's actual state of mind.
However, the Practice Statement has seldom been applied by the House of Lords, usually only as a last resort. As of 2005, the House of Lords has rejected its past decisions no more than 20 times. They are reluctant to use it because they fear to introduce uncertainty into the law. In particular, the Practice Statement stated that the Lords would especially be reluctant to overrule themselves in criminal cases because of the importance of certainty in the law here. The first case involving criminal law to be overruled with the Practice Statement was Anderton v Ryan (1985), which was overruled by R v Shivpuri (1986), two decades after the Practice Statement. Remarkably, the precedent overruled had been made only a year before, but it had been criticised by several academic lawyers. As a result, Lord Bridge stated he was "undeterred by the consideration that the decision in Anderton v Ryan was so recent. The Practice Statement is an effective abandonment of our pretention to infallibility. If a serious error embodied in a decision of this House has distorted the law, the sooner it is corrected the better. Still, the House of Lords has remained reluctant to overrule itself in some cases; in R v Kansal (2002), the majority of House members took the view that R v Lambert had been wrongly decided, but declined to depart from their earlier decision.
In the United States Supreme Court, the principle of stare decisis is most flexible in constitutional cases:
For example, in the years 1946–1992, the U.S. Supreme Court reversed itself in about 130 cases. The U.S. Supreme Court has further explained as follows:
The doctrine of binding precedent or stare decisis is central to the English legal system, and to the legal systems that derived from it such as those of Australia, Canada, Pakistan and New Zealand. A precedent is a statement made of the law by a Judge in deciding a case. The doctrine, states that within the hierarchy of the English courts a decision by a higher court will be binding on lower courts. This means that when judges try cases they will check to see if similar cases have come before a court previously. If there was a precedent set by an equal or higher court, then a judge should follow that precedent. If there is a precedent set in a lower court, a judge does not have to follow it, but may consider it. The House of Lords however does not have to follow its own precedents.
Only the statements of law are binding. This is known as the reason for the decision or ratio decidendi. All other reasons are "by the way" or obiter dictum. See Rondel v. Worsley  1 AC 191. A precedent does not bind a court if it finds there was a lack of care in the original “Per Incuriam”. For example, if a statutory provision or precedent had not been brought to the previous court's attention before its decision, the precedent would not be binding. Also, if a court finds a material difference between cases then it can choose not to be bound by the precedent. Persuasive precedents are those that have been set by courts lower in the hierarchy. They may be persuasive, but are not binding. Most importantly, precedents can be overruled by a subsequent decision by a higher court or by an Act of Parliament.
Judges in the UK use three primary rules for interpreting the law. The normal aids that a judge has include access to all previous cases in which a precedent has been set, and a good English dictionary.
Under the literal rule, the judge should do what the actual legislation says rather than trying to do what he or she thinks that it means. The judge should use the plain everyday ordinary meaning of the words, even if this produces an unjust or undesirable outcome. A good example of problems with this method is R v Maginnis (1987) in which several judges found several different dictionary meanings of the word "supply". Another example might be Fisher v Bell, where it was held that a shopkeeper who placed an illegal item in a shop window with a price tag did not make an offer to sell it, because of the specific meaning of "offer for sale" in contract law. As a result of this case, Parliament amended the statute concerned to close this loophole.
The golden rule is used when use of the literal rule would obviously create an absurd result. The court must find genuine difficulties before it declines to use the literal rule. There are two ways in which the Golden Rule can be applied: the narrow approach, and the broad approach. Under the narrow approach, when there are apparently two contradictory meanings to a word used in a legislative provision or it is ambiguous, the least absurd is to be used. For example, in Adler v George (1964), the defendant was found guilty under the Official Secrets Act of 1920. The court chose not to take the wording literally. Under the broad approach, the court may reinterpret the law at will when it is clear that there is only one way to read the statute. This occurred in Re Sigsworth (1935) where a man who murdered his mother was forbidden from inheriting her estate, despite a statute to the contrary.
The mischief rule is the most flexible of the interpretation methods. Stemming from Heydon's Case (1584), it allows the court to enforce what the statute is aimed at remedying rather than what the words actually say. For example, in Corkery v Carpenter (1950), a man was found guilty of being drunk in charge of a carriage, although in fact he only had a bicycle.
In the United States, the courts have consistently stated that the text of the statute is read as it is written, using the ordinary meaning of the words of the statute.
Courts may choose to follow precedents of other jurisdictions, but this is not an application of the doctrine of stare decisis, because foreign decisions are not binding. Rather, a foreign decision that is followed on the basis of the soundness of its reasoning will be called persuasive authority — indicating that its effect is limited to the persuasiveness of the reasons it provides.
The doctrine of jurisprudence constante also influences how court decisions are structured. In general, court decisions in common law jurisdictions are extremely wordy and go into great detail as to the how the decision was reached. This occurs to justify a court decision on the basis of previous case law as well as to make it easier to use the decision as a precedent in future cases.
By contrast, court decisions in some civil law jurisdictions (most prominently France) tend to be extremely brief, mentioning only the relevant legislation and not going into great detail about how a decision was reached. This is the result of the theoretical view that the court is only interpreting the view of the legislature and that detailed exposition is unnecessary. Because of this, much more of the exposition of the law is done by academic jurists which provide the explanations that in common law nations would be provided by the judges themselves.
In other civil law jurisdictions, such as the German-speaking countries, court opinions tend to be much longer than in France, and courts will frequently cite previous cases and academic writing. However, some courts (such as German courts) put less emphasis of the particular facts of the case than common law courts, but put more emphasis on the discussion of various doctrinal arguments and on finding what the correct interpretation of the law is.
Some originalists may go even further. In his confirmation hearings, Justice Clarence Thomas answered a question from Senator Strom Thurmond, qualifying his willingness to overturn precedent in this way:
Possibly he has changed his mind, or there are a very large body of cases which merit "the additional step" of ignoring the doctrine; according to Scalia, "Clarence Thomas doesn't believe in stare decisis, period. If a constitutional line of authority is wrong, he would say, let’s get it right.
Professor Caleb Nelson, a former clerk for Justice Thomas and law professor at the University of Virginia, has elaborated on the role of stare decisis in originalist jurisprudence:
While Posner and Landes' idea did not take hold, the term "super-precedent" has subsequently become synonymous with a different idea: the difficulty of overturning a decision. In 1992, Rutgers professor Earl Maltz criticized the Supreme Court's decision in Planned Parenthood v. Casey for endorsing the idea that if one side can take control of the Court on an issue of major national importance (as in Roe v. Wade), then that side can protect its position from being reversed "by a kind of super-stare decisis. The controversial idea that some decisions are virtually immune from being overturned, regardless of whether they were correctly decided in the first place, is the idea to which the term "super stare decisis" now usually refers.
The concept of super-stare decisis (or “super-precedent”) arose anew in relation to the interrogations of Chief Justice John Roberts and Justice Samuel Alito before the Senate Judiciary Committee. Prior to the commencement of the Roberts hearings, the chair of that committee, Senator Arlen Specter of Pennsylvania, wrote an op/ed in the New York Times referring to Roe as a "super-precedent." He revisited this concept (and perhaps humorously expanded it to "super-duper precedent") during the hearings, but neither Roberts nor Alito endorsed the term or the concept.
Lastly, super-stare decisis (or super-duper stare decisis) may be viewed as one extreme in a range of precedential power.
Regarding constitutional interpretations, there is concern that over-reliance on the doctrine of stare decisis can be subversive. An erroneous precedent may at first be only slightly inconsistent with the Constitution, and then this error in interpretation can be propagated and built upon by further precedents until a result is obtained that is far outside the bounds of original understanding of the Constitution. Stare decisis is not mandated by the Constitution, and if it leads to unconstitutional results then the historical evidence of original understanding can be re-examined. In this view, predictable fidelity to the Constitution is more important than fidelity to unconstitutional precedents.