Precedent

"Legal Lexicon":
PRECEDENT - Legal principle, created by a court decision, which provides an example or authority for judges deciding similar issues later. Generally, decisions of higher courts (within a particular system of courts) are mandatory precedent on lower courts within that system--that is, the principle announced by a higher court must be followed in later cases. For example, the California Supreme Court decision that unmarried people who live together may enter into cohabitation agreements (Marvin v. Marvin), is binding on all appellate courts and trial courts in California (which are lower courts in relation to the California Supreme Court). Similarly, decisions of the U.S. Supreme Court (the highest court in the country) are generally binding on all other courts in the U.S.
Decisions of lower courts are not binding on higher courts, although from time to time a higher court will adopt the reasoning and conclusion of a lower court. Decisions by courts of the same level (usually appellate courts) are considered persuasive authority. That is, they should always be carefully considered by the later court but need not be followed.
As a practical matter, courts can usually find precedent for any direction they want to go in deciding a particular case. Accordingly, precedent is used as often to justify a particular outcome in a case as it is to guide the decision.
The body of judicial decisions in which were formulated the points of law arising in any case. A previously decided case that is considered binding in the court where it was issued and in all lower courts in the same jurisdiction.
A court decision in an earlier case with facts and law similar to a dispute currently before a court. Precedent will ordinarily govern the decision of a later similar case, unless a party can show that it was wrongly decided or that it differed in some significant way.
The decision of courts of justice when exactly in point with a case before the court are generally held to have a binding authority, as well to keep the scale of justice even and steady because the law in that case has been solemnly declared and determined.
To render precedents valid they must be founded in reason and justice; must have been made upon argument, and be the solemn decision of the court; and in order to give them binding effect there must be a current of decisions.
According to Lord Talbot, it is "much better to stick to the known general rules than to follow any one particular precedent which may be founded on reason unknown to us." Blackstone says, that a former decision is in general to be followed unless "manifestly absurd or unjust," and, in the latter case, it is declared when overruled not that the former sentence was bad law, but that it was not law.
Precedents can only be useful when they show that the case has been decided upon a certain principle and ought not to be binding when contrary to such principle. If a precedent is to be followed because it is a precedent, even when decided against an established rule of law, there can be no possible correction of abuses because the fact of their existence renders them above the law. It is always safe to rely upon principles.
"In Law, a previous decision, rule or practice which, in the absence of a definite statute, has whatever force and authority a Judge may choose to give it, thereby greatly simplifying his task of doing as he pleases. As there are precedents for everything, he has only to ignore those that make against his interest and accentuate those in the line of his desire. Invention of the precedent elevates the trial-at-law from the low estate of a fortuitous ordeal to the noble attitude of a dirigible arbitrament." -- Ambrose Bierce
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