Definition
A French phrase meaning, literally, a fortuitous event or inevitable accident. In legal usage, cas fortuit denotes an occurrence so beyond the ordinary course of events and so entirely outside a party's control that it excuses performance of an obligation or negates liability for resulting harm. The term appears most frequently in the law of insurance, where it describes an event that is accidental in the strict sense — not merely unexpected, but genuinely unforeseeable and unavoidable — such that it falls outside the scope of risk a party could be held to have assumed or guarded against.
Cas fortuit is the French-law counterpart to the Latin casus fortuitus and the common-law concept of act of God or force majeure. In civil-law jurisdictions and in insurance contexts with civilian influence, the phrase is sometimes used interchangeably with force majeure, though the two concepts carry distinct technical weight in their original frameworks.
Common Confusion
Cas fortuit, casus fortuitus, force majeure, and act of God are frequently treated as synonyms, but they are not identical. Cas fortuit and casus fortuitus are the same concept in French and Latin dress, respectively — both emphasize pure accident and the absence of human fault. Force majeure (superior force) focuses on external compulsion: a force so overwhelming that performance is rendered impossible regardless of the party's diligence. Act of God is the common-law analogue, typically limited to natural phenomena entirely beyond human intervention. In research, conflating these terms risks misreading the scope of an excuse or defense: a cas fortuit need not be a natural event, while an act of God usually must be. In civilian-influenced jurisdictions such as Louisiana, the distinctions retain practical legal weight.
Why It Matters in Research
Researchers will encounter cas fortuit most often in three contexts: (1) historical insurance law materials, particularly those drawing on French and continental European sources; (2) Louisiana law and other American jurisdictions with civilian heritage, where the French term appears in primary sources and commentary; and (3) comparative law scholarship analyzing the common-law/civil-law divide on excused nonperformance.
The key navigational trap is terminological layering. A single nineteenth-century treatise or case may use cas fortuit, casus fortuitus, act of God, and force majeure within adjacent paragraphs, sometimes interchangeably and sometimes with intended distinctions. Burrill cites Emerigon's Traité des Assurances and Kent's Commentaries — both standard reference points for the era — signaling that the term entered American legal vocabulary primarily through insurance doctrine influenced by French maritime law. Researchers working in early American insurance cases should check whether the court is drawing on civilian or common-law principles, as this affects which doctrine governs the scope of the excuse.
In modern research databases, cas fortuit may be indexed under force majeure, act of God, or impossibility of performance rather than by the French phrase itself. Searching only the French term will produce incomplete results; cross-searching casus fortuitus and force majeure is essential for comprehensive retrieval.
Historical Dictionary Support
The historical dictionaries are notably sparse on this term. Black's (both editions) and Burrill agree on a one-line definition: a fortuitous event; an inevitable accident, situated in the law of insurance. Burrill adds the only substantive citation trail, pointing to Emerigon and Kent — two sources that would have been authoritative for American lawyers working with marine insurance in the nineteenth century. Rapalje & Lawrence redirect entirely to casus fortuitus, which is the more common entry point in Latin-form dictionaries.
What the historical dictionaries do not capture is the conceptual tension between cas fortuit (pure accident, no fault) and force majeure (irresistible external force). That distinction is addressed in French civil-law sources and in comparative treatises but is absent from the American legal dictionary tradition, which treated the terms as functional equivalents. Modern scholarship has sharpened the distinction considerably.
Jurisdictional Note
Louisiana courts and practitioners are most likely to use cas fortuit as a live term of art, given the state's civilian heritage. In other American jurisdictions, the concept survives in the doctrines of act of God, impossibility, and force majeure, but the French phrase itself is unlikely to appear in modern primary sources outside of quotation or historical analysis.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Force Majeure; Act of God; Impossibility of Performance; Insurance Law — Excused Loss.