The party taking an appeal from a lower court decision is required to specify the "errors" which they allege that the lower court made in deciding the case. Those errors can involve questions of law and questions of fact. The court of appeal requires that the party who takes the appeal must prove that the lower court was wrong using certain standards.
Generally, if the alleged error involves a question of fact or a credibility call between witnesses, the court of appeal places a heavier burden on the appealing party to demonstrate that the lower court was wrong. Usually, an appellate court may reverse a lower court's factual findings when the record reflects that a reasonable factual basis does not exist for the finding of the trial court or, the record reflects that the finding is clearly wrong.
In such instances, the court of appeal gives great deference to findings of fact by the trial court. Even if the court of appeal disagrees with the factual findings of the lower court or, would have decided the case differently under the same facts, the court of appeal is not allowed to substitute its own judgment for the judgment of the lower court. It must uphold the lower court's decision.
The reason for this deference is that the trial court actually sat and heard the witnesses and could more readily evaluate their credibility. Remember, the court of appeal reviews only the type written transcript of the trial and the exhibits admitted into evidence. It does not hear from live witnesses. The transcript and exhibits are referred to as the "record." This record is the only item reviewed by the court of appeal. If evidence or argument is not in the record, it does not get considered.
If the alleged error of the trial court is an error in the application of the law, the court of appeal generally does not have to give deference to the lower court's decision. The court of appeal can decide for itself whether the correct law was used in deciding the case.
If the court of appeal finds that the party appealing (the appellant), has met its burden of demonstrating that the lower court was wrong, it has several options. It can reverse the lower court's decision and order that the case be retried applying the correct law. It can reverse the lower court's decision and render its own decision based upon a review of the evidence. It can remand (return) the case to the lower court with instructions to do something differently or to reconsider an issue in light of its findings.
If the issue on appeal relates to damages, the court of appeal can decrease, increase or affirm the damages awarded by the lower court. In considering this issue, the court reviews previous awards for similar injuries or claims and then determines whether the award of the lower court falls within an acceptable range of verdicts previously rendered on the subject. Generally, if the lower court verdict falls within that range, even if it is on the high side or low side of the range, the court of appeal will affirm the decision of the lower court.
In terms of procedure, the person appealing the case has the burden of asking the lower court to transcribe the testimony taken by the court reporter at trial and preparing the record to be "lodged" (sent) to the court of appeal for review. The appellant's brief is due first. The appellee (the person who won in the lower court), gets a period to review that brief and file his own brief in response. The court then may or may not want the parties to appear before it to hear the lawyers argue their positions or to question them on specific issues.
The court then makes a decision and usually designates one of the appeal justices to write the opinion of the court. Judges who do not agree with the decision can write a dissent, which is basically their reasons for disagreeing with the majority of the other deciding justices.