The Latin expression mala in se literally means “bad in themselves.” It is a term used in criminal law to distinguish a type of crime that is morally wrong by its nature and by society's moral judgment and need not be proven or legislated to be wrong. Most often, these crimes lead to serious harm of people and/or property. Examples of mala in se crimes include murder, robbery, burglary, and rape.
In the past, mala in se crimes were often punished by death, but today's law codes often take into consideration other factors besides this classification when determining punishments.
Mala in se crimes are distinguished from mala prohibita, “bad because prohibited,” crimes. The latter are crimes because their actions violate a statute or law that prohibits such acts. For instance, if you park in a no-parking zone, even for a few minutes, you are guilty of a mala prohibita crime. You aren't necessarily causing harm to anyone, and society does not judge your act to be a serious moral wrong, but you have violated a state or city law. Other mala prohibita crimes include cheating on taxes, traffic violations, and illegal gambling. Note that because laws can be changed, mala prohibita crimes can vary over time and from place to place.