When the losing party believes that the trial court made mistakes in applying the law, it appeals. The thumb-rule of appeal is that the prevailing party cannot appeal.
Unlike in civil law countries, in our common law system, the facts are not contested on appeal. No additional testimony is taken, nor is new evidence submitted.
The opinions of the appellate courts rest on the trial record and the memoranda of law that the lawyers submit when asking for the appeal (or defending themselves against the appeal). The two basic functions of appellate courts are to review the trial court record and establish whether a reversible error occurred at the trial level.
Harmless errors are not grounds for appeal. Thus, “When the plaintiff has been granted all available relief, any error that the plaintiff complains of is harmless.”
The court of appeals’ opinions are written by the assigned judge, but are filed as the opinion of the court. Usually they end the controversy (as very few reach the court of last resort, especially at the federal level) and establish the precedent for following cases. Thus, judge-made law, also known as decisional law, or case law, does not mean the totality of our court opinions. It rarely means decisions found in trial court opinions. In other words, judge-made law covers all final court decisions and is built on previous decisions through the principle of stare decisis, which requires courts in subsequent decisions to follow the holding in previous cases.
By now you know that case law is decisions that come from intermediary courts and the courts of last resort. Because these decisions cannot be challenged any further, they have the authority to resolve the dispute that caused them once and for all. In addition, they have the authority to regulate the future in similar circumstances. That authority rests on policies of security and certainty that are translated in law under the doctrine of stare decisis. Regulating the future through court decisions is a unique feature of the common law system due to its cornerstone principle—stare decisis.
For all these reasons, these decisions are made public in print and digital reporters and since 2002, on the courts' web sites.