A miscarriage of justice primarily is the conviction and punishment of a person for a crime they did not commit. The term can also apply to errors in the other direction—"errors of impunity", and to civil cases. Most criminal justice systems have some means to overturn, or "quash", a wrongful conviction, but this is often difficult to achieve. In some instances a wrongful conviction is not overturned for several years, or until after the innocent person has been executed, released from custody, or has died.