The remaining part of the system of courts for criminal matters is concerned with criminal appeals. Before describing the courts which deal with these it is worth considering what the purpose of criminal appeal is supposed to be, and what functions we would expect courts of criminal appeal to perform in an ideal legal world. Broadly speaking, the main function of criminal appeal must surely be to see that the trial in the court of first instance reached the correct result, and to put the matter right if it did not. From the defendant's point of view, this means quashing the conviction and substituting an acquittal where he was innocent, and where he was guilty, reducing the sentence if it was unreasonably severe. From the prosecution's point of view it means the converse – substituting convictions for undeserved acquittals, and increasing sentences which are unreasonably light. But there is also a secondary purpose in a system of criminal appeals, and that is to safeguard the integrity of the system of criminal justice by making sure that criminal cases are tried according to due process of law. For example, every defendant, however manifestly guilty and no matter how vile, surely has a legitimate complaint if he was convicted on the basis of a confession extracted from him by torture, or by a jury consisting of a panel of his victims, presided over by a judge who was the brother of the policeman who investigated the case.