Our federal legal system is based on two things: The Constitution and the United States Code, the “official compilation and codification of general and permanent federal statutory law.”

But our courts have roots dating back to England and before that, to ancient Rome. In fact, some of our current laws have roots in old Roman law. This is why Latin is still used in our courts.

While there are numerous- perhaps hundreds- of legal terms that are Latin or have Latin roots, here are three that are most relevant to criminal defense.

  • Mens rea: This means “guilty mind”.  In order for someone to commit a crime, he or she must have criminal intent. The second part of this is actus reus, the guilt act. Children  and those with severely limited mental capabilities cannot knowingly commit a crime and therefore cannot be criminally responsible.
  • Modus operandi: A person’s way of acting in committing the charged offense. This can be applied to behavioral analysis in the investigation of a crime. It is often referred to as “M.O.”
  • Malum in se: Defined as evil in itself or wrong in itself. We consider rape, murder and robbery to be wrong, not because there are laws against these acts, but because they cause grave harm. A related term is malum prohibitum, which means that something is not immoral or evil in itself, but is wrong because there is a law against it. A 1995 Washington University Law Review article goes into great detail about the difference. An example of malum prohibitum may be drinking alcohol on the street. It’s only wrong because there is a law against it.

Malum prohibitum laws can extend to the extreme or absurd. Until 1986, for example, it was illegal to eat ice cream on the streets of Carmel, California. While not entirely practical, knowing the root and meaning of Latin words can enhance not only your mental cache of trivia, but also your legal vocabulary.