Definition
Latin: "wrong in itself." An act that is inherently and essentially evil — immoral in its nature and injurious in its consequences — independent of any statute or positive law declaring it so. An act is malum in se not because a legislature has prohibited it, but because it violates natural law, moral principles, or universal standards of human conduct. Murder, rape, robbery, and arson are classic examples: their wrongfulness exists prior to and apart from any legal prohibition.
The concept operates as the traditional counterpart to malum prohibitum — wrongs that are illegal only because a governing authority has declared them so, not because the act is inherently wicked.
Common Language
Wiktionary: "A wrong in itself; that which is injurious in its consequence. The Latin phrase used in law to refer to crimes that are illegal from the nature of crime, that is, inherently evil without any fact of being noticed or punished, as opposed to malum prohibitum."
The Wiktionary definition is accurate as far as it goes, but researchers should note that the common gloss — "wrong in itself" — understates the doctrinal freight the phrase carries. In legal usage, the malum in se / malum prohibitum distinction is not merely descriptive; it determines substantive outcomes across criminal law, tort law, and agency doctrine. Whether an act falls into one category or the other can affect the degree of criminal intent required, the availability of certain defenses, and whether a statutory violation automatically generates civil liability.
Common Confusion
Malum in se is frequently set against malum prohibitum without sufficient attention to how contested and unstable the boundary between them is. The distinction sounds categorical but has always been contested in application. Courts and scholars have disagreed about where drug offenses, regulatory crimes, and public welfare offenses belong. A researcher encountering either phrase in historical sources should not assume a fixed or shared taxonomy — the line has shifted with moral consensus, legislative expansion, and judicial temperament. The distinction is also sometimes confused with the mens rea / strict liability axis, which overlaps it but is not identical: a malum prohibitum offense can still require intent, and the categorization does not automatically determine the mental state required for conviction.
Why It Matters in Research
The malum in se / malum prohibitum distinction appears across at least four major doctrinal contexts in the Law Mind corpus, and researchers moving between them risk applying context-specific reasoning where it does not belong.
In criminal law, the distinction historically tracked the common law baseline: malum in se offenses were punishable without statutory authorization; malum prohibitum offenses required positive enactment. This matters for reading pre-codification cases and treatises, where the category determined whether courts would recognize the offense at all.
In tort law, the distinction is load-bearing in negligence per se analysis. Some courts hold that violation of a statute constitutes negligence per se only when the underlying act is malum in se; others apply per se treatment to any statutory violation meeting the proximate-cause and class-of-persons tests. Researchers should not assume uniformity.
In agency and contract law — where Story's Ag. § 346 appears in both Black's and Burrill's — the distinction determines whether an agent's unauthorized act binds the principal or voids the transaction entirely. Contracts involving acts malum in se are void, not merely voidable. This is a recurring trap in historical commercial law cases.
In defamation law, the concept of defamation "per se" (statements actionable without proof of special damages) is sometimes discussed in terms derived from malum in se reasoning — that certain statements are so inherently damaging that injury is presumed. Researchers should be alert to the terminological overlap between "per se" in defamation doctrine and the malum in se category, which are related in intellectual genealogy but distinct in operation.
Historical sources frequently treat the category as self-evident — listing examples rather than supplying criteria. This obscures real difficulty in classifying edge cases and means that nineteenth-century authority should be read with attention to the specific doctrinal context in which the phrase appears.
Historical Dictionary Support
Black's and Burrill's are in close agreement, with Burrill's adding the alternate form malum per se (citing Vaughan 332) — a synonym that appears in older common law materials and may cause retrieval difficulties in corpus searches if only one form is indexed. Both cite Story on Agency § 346, anchoring the term's formal legal use in the agency context specifically.
The Bouvier's excerpt provided does not contain a direct entry for malum in se; the text appears to relate to malicious prosecution, suggesting either a scanning artifact or an indexing issue in the source material. Researchers relying on Bouvier's for this term should verify the entry independently.
What the historical dictionaries do not supply is any workable test for classifying an act. They define by example and by reference to "natural, moral, and public law" — a standard that imports the moral consensus of the era without acknowledging that consensus as contingent. This is significant: the historical entries were written when common law crimes were still recognized in many American jurisdictions, and the malum in se category carried real operative weight that it has largely lost under modern statutory codes.
Jurisdictional Note
The practical significance of the malum in se / malum prohibitum distinction varies substantially by jurisdiction and by the doctrine at issue. In states that have abolished common law crimes entirely, the distinction survives mainly in tort and contract analysis. In jurisdictions retaining common law criminal authority, it may still affect whether an uncharged act can ground civil liability or a lesser-included-offense instruction.
Encyclopedia Cross-Reference
The Law Mind Torts & Personal Injury Encyclopedia: Negligence — Negligence Per Se (Violation of Statute as Negligence) [torts_8]
The Law Mind Torts & Personal Injury Encyclopedia: Defamation and Privacy Torts — Defamation Per Se Categories [torts_123]