Definition
Concussio (Latin; also rendered in English as concussion) is a term from Roman civil law denoting the act of extorting money or property from a person by threats of violence. The wrongdoer compels the victim to surrender something of value not by actual force but by the fear of force — a coercive demand backed by threatened harm rather than completed assault. In classical Roman law, concussio was treated as a distinct delict, distinguishable from outright robbery (rapina) by its reliance on intimidation rather than physical taking, and from simple theft (furtum) by the element of open menace.
The term entered the vocabulary of civil-law jurisdictions and legal scholarship primarily through Roman law sources, including the Digest of Justinian, which treated concussio as actionable conduct giving rise to a private remedy as well as potential public prosecution. In its narrowest sense it describes the conduct of a private actor; in some usages it extended to the misconduct of officials who leveraged their public authority to extort compliance — a concept that bleeds into what later legal systems would call extortion or official oppression.
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Common Language
Modern common usage (Wiktionary): "Concussion" in everyday English refers almost exclusively to a traumatic brain injury caused by a blow or jolt to the head, producing temporary neurological impairment.
Historical common usage (Webster's 1913): Webster's 1913 gives "concussion" two senses: (1) a violent shock or agitation; (2) a condition of the brain resulting from a violent blow or jar.
The gap between common and legal meaning here is nearly total. In legal — specifically civil-law — usage, concussio/concussion has nothing to do with physical injury to the body. It describes a form of coercive extortion. A researcher encountering "concussion" in a legal text drawn from Roman law or a civil-law jurisdiction should not assume any medical or physical-injury meaning. The term belongs to the law of obligations and wrongs, not personal injury.
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Common Confusion
Concussio is sometimes loosely equated with extortio (extortion) or metus (duress/fear), but these are technically distinct concepts in Roman law. Extortio implied wringing out by force; metus was the mental state of fear that could vitiate consent in contracts. Concussio occupied a middle position — it was the wrongful act of inducing that fear for personal gain, closer to what modern law calls extortion or criminal coercion. Researchers should not treat these terms as interchangeable when reading Roman law sources carefully.
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Why It Matters in Research
This term is a navigational trap for researchers trained in common-law systems. The word "concussion" appearing in any text touching Roman law, civil-law commentary, or early modern legal scholarship almost certainly carries the extortion meaning, not the medical one. The risk of misreading is high because modern readers instinctively supply the medical definition.
In the Law Mind corpus, concussio is most likely to surface in: (1) Roman law treatises and Digest commentary; (2) historical works on civil-law obligations and delicts; (3) comparative law discussions of extortion, coercion, and duress; and (4) early American and English legal dictionaries that preserved civil-law vocabulary as part of the general legal lexicon, as Rapalje & Lawrence does here.
The term has no continuing operational life in modern American common law. It does not appear in statutes, jury instructions, or contemporary case law in its legal sense. Its value in research is therefore historical and comparative — understanding what Roman and civil-law sources mean when they use the word, and tracing how modern concepts of extortion, duress, and coercion descend from or diverge from the Roman framework.
Researchers pursuing the history of extortion law, coercion as a defense to contract, or official misconduct in civil-law systems will encounter concussio as a foundational reference point.
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Historical Dictionary Support
Rapalje & Lawrence give a terse but accurate entry: "In the civil law, extortion by threats of violence." This is consistent with the classical Roman law understanding. The brevity is characteristic of their treatment of pure civil-law terms — they flag the concept for identification but do not elaborate the doctrinal detail.
What Rapalje & Lawrence do not provide — and what the entry's placement immediately before CONDEMN quietly signals — is any discussion of the delict's structure, its relationship to the actio quod metus causa (the action based on fear-induced conduct), or its distinction from metus in contract law. Researchers needing doctrinal depth beyond identification will need to move from Rapalje & Lawrence to Roman law sources directly.
Historical dictionaries in the common-law tradition generally treat concussio as a term of art requiring identification rather than sustained analysis, reflecting its status as a borrowed civil-law concept rather than a living common-law doctrine.
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Jurisdictional Note
Concussio as a legal term of art is a civil-law concept with no direct common-law counterpart. Modern civil-law jurisdictions do not use the Roman term operationally but descended from it in their criminal and delictual treatment of extortion and coercion. Louisiana, as the primary American civil-law jurisdiction, may surface this term in historical legal scholarship, but it does not appear in contemporary Louisiana statutory or case law by this name.
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