Malum in se is a Latin phrase meaning wrong in itself. It is a term used to describe something that is inherently immoral, regardless of whether it is defined by law as illegal. Crimes such as larceny, rape and murder are considered malum in se. This concept was used to develop the various common-law crimes. It is distinguished from malum prohibitum or wrongs that are only wrong by statute, such as parking violations.
For example murder of human beings is universally agreed to be a wrong regardless of whether a law exists making it a crime. Therefore it is Malum in se. On the other hand violation of driving laws are malum prohibitum law because the act is not inherently bad, but is forbidden by policy, set forth by the policy-makers of the jurisdiction.
Mala in se is the plural of Malum in se.