非常上訴係針對刑事判決確定後，原確定判決所適用法律有所違誤，由最高檢察署檢察總長向最高法院提起之特別救濟程序。亦即：非常上訴之目的，旨在統一法令之解釋與適用為原則，只有在例外之原判決不利於被告，為了救濟被告起見，於撤銷原判決，另行改判時，效力始及於被告；故原判決有無不利於被告，乃涉及撤銷改判之問題，對被告權益之影響甚鉅。因此，本系爭法律問題，雖然原判決適用法令有違誤，但有無必要撤銷改判，涉及二個重要爭點：一、「不利益變更禁止原則」之法理；二、「原判決利或不利於被告」之判斷標準為何，均為本文之焦點。

The Extraordinary Appeal is the special relief filed by Prosecutor-General of Supreme Court Prosecutors' Office to Supreme Court when a final criminal judgment was found to be erroneous on the operation of law, namely the purpose of Extraordinary Appeal is, in principle, to unify the interpretation and application of laws and regulations with an exception when the decision of the first instance is adverse to the Defendant and the alternation of such a decision may be subject to some limitation in favor of the Defendant's relief. Therefore whether or not the decision of the first instance is adverse to the Defendant may concern the alteration of subsequent instances and will have a major impact to the Defendant's legal rights. In sum, the underlying legal question to the necessity of relief alteration towards the decision found erroneous on the operation of law will be twofold, the legal theory of the principle of adverse alternation prohibition and the criteria of decision adversity against the Defendant. Both of the aforementioned twofold are the subjects of this study.