A criminal appeal is a formal request to rehear a case that has already been decided -- a request that a new court reconsider the decision of the first court. When one or both sides of a case that has already been decided think there was a mistake made at trial, they can file an appeal. An appeal is entirely different than a jury trial. There is no testimony taken. The court of appeals decides the case entirely upon the written briefs filed by your attorney and the offie of the Attorney General who represents the prosecution and asks that the conviction be upheld.