A reformatio in peius (Latin: "change for the worse") occurs in law when as the result of an appeal, the appellant is put in a worse position than if there had been no appeal. For example, an appellant in a criminal case might receive a more severe sentence on appeal than in their original trial.
Whether or not reformationes in peius are allowed depends on the jurisdiction and the applicable procedural law. In civil law jurisdictions, reformationes in peius are generally not allowed in appeals in administrative law cases and in criminal and civil appeals if the “other” party, i.e. the state in a criminal case, appeals the decision.[citation needed] Thus, a defendant needs never fear appeal an unjust conviction, such as a guilty verdict; a negative shift, such as a more severe penalty, can only result from the prosecution appealing it (as well).