An ex post facto law (from the Latin for "from after the action" or "after the fact") or retroactive law is a law that retroactively changes the legal consequences (or status) of actions committed or relationships that existed prior to the enactment of the law. In reference to criminal law, it may criminalize actions that were legal when committed; or it may aggravate a crime by bringing it into a more severe category than it was in at the time it was committed; or it may change or increase the punishment prescribed for a crime, such as by adding new penalties or extending terms; or it may alter the rules of evidence in order to make conviction for a crime more likely than it would have been at the time of the action for which a defendant is prosecuted. Conversely, a form of ex post facto law commonly known as an amnesty law may decriminalize certain acts or alleviate possible punishments (for example by replacing the death sentence with lifelong imprisonment) retroactively. Such laws are also known by the Latin term In mitius.