One of the major differences between the American (and British) systems of justice – the adversarial system – and the system used in countries that have adopted the Roman civil law system is the way appeals operate.
In North Carolina, for instance, after the trier of fact – usually a jury – renders a general verdict in a case, that case is (usually) final with respect to the facts, so long as the there were facts in the record that could’ve supported the verdict and the verdict was not irrational or unreasoanble.
In addition, upon review, a court of appeals in North Carolina or the federal system views the facts in the light most favorable to the prosecution.
Courts of appeals will conduct a de novo review of questions of law. For instance, whether evidence was admissible in the first place is a question of law, and therefore the reviewing court will conduct a new review of that decision to decide whether or not the evidence should’ve been admitted.
But, because courts of appeals in the United States and North Carolina do not generally review the facts of the case, decisions which may be erroneous, because juries have made mistakes or misjudged evidence, will stand unless the jury’s decision was clearly irrational.
Contrast this situation with the Amanda Knox case in Italy. Knox was accused of killing a British student Meredith Kercher. The lower level Italian court found Knox guilty based on faulty DNA analysis performed by the prosecution’s witness. But the appeals court in Italy hears the evidence again, and when they did they found that Knox and her former boyfriend were not guilty of the crime.