Definition
Latin. Evil; wrong; an offense. In legal usage, malum functions primarily as a prefix or standalone term denoting that something is wrongful in character. It appears most frequently as part of the compound phrases malum in se and malum prohibitum, which classify the nature of a legal wrong. As a standalone term, malum means an evil act or wrong, and carries the sense that the act is inherently bad or injurious rather than merely irregular.
In older English common law procedure, malum was also used in the law of essoins to mean a misfortune or sudden infirmity preventing a party from appearing in court when summoned — a usage entirely unconnected to its moral or criminal sense.
Common Language
Modern common usage (Wiktionary): An evil or wrongdoing.
Historical common usage (Webster's 1913): An evil. See Mala.
The common and legal meanings align closely, but the legal term carries structural weight that the common usage does not. In law, malum rarely travels alone; it is the root of a taxonomy that divides wrongs by their origin — whether in nature or in statute. A researcher who encounters malum in isolation should treat it as a signal to look for the completing phrase.
Common Confusion
Malum is most often confused with its two derivative phrases, malum in se and malum prohibitum, which are the terms doing real work in legal argument. Malum alone does not specify which category of wrong is meant. Additionally, Black's Law Dictionary records a separate Latin term spelled identically — malum meaning the mast of a ship in Roman law — which is a wholly unrelated term from Roman commercial and maritime law. A researcher working in Roman law sources or Digest materials should be alert to this homonym.
Recognized Forms
/SUBTYPES
The term generates two major legal compounds that carry the practical doctrinal content:
MALUM IN SE — An act wrong in itself; wrongful by its nature, independent of any prohibition by positive law. Acts universally recognized as immoral or harmful regardless of statute.
MALUM PROHIBITUM — An act wrong because it is prohibited by law; not inherently immoral, but made unlawful by legislative command.
These are the operative legal forms. Malum standing alone is essentially the root from which these distinctions grow.
Why It Matters in Research
Researchers will almost never need malum as a standalone entry — its significance is navigational. Encountering malum in a historical source is a cue to locate the full phrase. Pre-twentieth-century legal writing, especially in criminal law treatises and common law opinions, uses malum in se and malum prohibitum as load-bearing distinctions affecting mens rea requirements, accessory liability, and the permissibility of certain defenses. These distinctions have eroded in modern statutory criminal law, so older sources and modern sources use the terms with different stakes attached.
The essoin usage — malum as infirmity or misfortune excusing court appearance — belongs to a procedural world that has not survived. Researchers in medieval English legal records or early common law pleading materials may encounter this usage; it should not be read back into criminal or moral contexts.
The Roman law meaning (mast of a ship) appears in the Digest and will surface in any corpus containing Roman law source materials. It is a false cognate for purposes of legal philosophy or criminal law research.
Historical Dictionary Support
The three source dictionaries present strikingly different pictures of the same word, which itself reflects the term's ambiguity.
Black's records only the Roman law maritime meaning — the mast of a ship — citing Digest 50.17.242, and nothing else. This is an unusual editorial choice and suggests Black's treated the standalone term as adequately handled by its compound descendants (malum in se, malum prohibitum), which receive their own entries.
Anderson's Dictionary of Law defers entirely, redirecting to MALUS, its adjectival form.
Burrill's is the most useful of the three for legal research purposes, offering the moral and procedural senses: evil, wickedness, offense or wrong, as well as the essoin usage. Burrill also preserves two Latin maxims: Malum non praesuminur (wickedness is not presumed) — a presumption of good faith or innocence traceable to Coke and Broom's legal maxims — and Malum quo communius eo pejus (the more common an evil, the worse it is), a rhetorical and moral principle sometimes cited in arguments about public wrongs.
No source adequately synthesizes the term's full range or flags the homonym problem. Researchers should treat the historical dictionaries as starting points requiring triangulation.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Malum in Se and Malum Prohibitum; Criminal Intent and Mens Rea; Essoins and Common Law Procedure.