Definition
An unforeseeable event or accident beyond human anticipation or control, and the loss resulting from it. In law, the term operates primarily in two registers:
1. General legal usage: A casualty is an inevitable accident — an event that could not reasonably have been foreseen or guarded against. The term describes both the event itself and the loss it produces. Fire, shipwreck, and lightning strike the standard examples in historical authorities. In this sense, casualty overlaps substantially with act of God and force majeure, though the terms are not perfectly synonymous.
2. Tax law: A casualty is a sudden, unexpected, or unusual event that causes damage to or destruction of property. Under federal tax law, qualified casualty losses may be deductible, subject to significant statutory limitations. The tax definition has been refined legislatively and administratively to distinguish casual and sudden events from gradual deterioration. After 2017, personal casualty loss deductions are largely limited to federally declared disasters.
Common Language
Modern common usage (Wiktionary): An unfortunate accident or disaster; a person killed or injured in an accident or conflict; in military contexts, any person rendered unavailable for duty by death, wounds, illness, or capture.
Historical common usage (Webster's 1913): That which comes without design or without being foreseen; a contingency. Also, any injury of the body from accident, or a death occasioned by accident. In military usage, numerical loss caused by death, wounds, discharge, or desertion.
The common meaning has drifted significantly toward the human victim — a casualty is now commonly understood as a person harmed or killed, not the event causing the harm. Legal usage, especially in older authorities and insurance and bailment law, emphasizes the event or the resulting loss to property, not the injured person. A researcher reading historical legal sources should not import the modern common assumption that casualty refers to a person.
Recognized Forms
/SUBTYPES
Casualty Insurance: A broad category of insurance covering loss or liability arising from accidents, as distinguished from life or property insurance in its traditional sense. The term appears in Bouvier with a cross-reference, and casualty insurance has since developed into a distinct and sprawling commercial field.
Casualty Loss (Tax): The specific statutory and regulatory concept governing deductibility of losses from sudden, unexpected events. Distinguished from the general common-law meaning by detailed administrative requirements around suddenness, taxpayer causation, and, post-2017, federal disaster declarations.
Why It Matters in Research
The term carries different weights depending on the legal context in which it appears, and researchers must be alert to context before treating it as a fixed concept.
In insurance and bailment materials: Casualty means the precipitating event, not the victim. When older insurance treatises or bailment authorities discuss casualty, they are asking whether a loss arose from an unforeseeable, unavoidable event — not whether a person was harmed. Liability-shifting turns on that classification, and the doctrinal overlap with act of God and vis major is dense enough to require consulting those entries in parallel.
In tax materials: The evolution of the casualty loss deduction is a significant research trap. Pre-1986 authorities may discuss deductions under rules that no longer apply. The Tax Cuts and Jobs Act of 2017 imposed the federal disaster declaration requirement for personal casualty losses, drastically narrowing deductibility. Research using materials from before that date will overstate the availability of the deduction for individual taxpayers.
In military and administrative law: Casualty appears in its ordinary modern sense (person unavailable for duty), which diverges sharply from the property-loss-event meaning in civil law. Cross-context confusion is easy when documents from different legal fields are read together.
In historical sources generally: The term's migration from event to victim has been gradual and is not complete in legal usage. A nineteenth-century judicial opinion using "casualty" almost certainly means the unforeseeable event or resulting property loss, not a human victim.
Historical Dictionary Support
The historical dictionaries are in close agreement on the core definition. Black's (both editions), Bouvier, and Burrill all track Story on Bailments § 240, defining casualty as inevitable accident — an event not to be foreseen or guarded against — and specifically including the loss resulting from such an event. The examples given (fire, shipwreck, lightning) are consistent across sources and reflect the bailment and insurance contexts in which the term was most actively litigated.
Bouvier adds a Kentucky citation (129 Ky. 477) for the proposition that casualty also encompasses "that which happens without design or without being foreseen," a formulation that slightly expands the definition beyond strict inevitability toward simple unforeseeability. This nuance matters: strict inevitability sets a higher bar than mere unforeseeability, and courts have not always used the terms consistently.
Rapalje & Lawrence is the most spare, equating casualty simply with accident and cross-referencing that entry. This reflects a common-law tradition of treating the terms as interchangeable, which they are not always. Accident often implies a degree of human involvement or negligence; casualty in its strongest historical sense implies none.
What the historical dictionaries largely omit: the tax law dimension entirely. The casualty loss deduction, now one of the most practically significant legal contexts in which the term appears for non-commercial research, postdates these authorities. Researchers should not expect guidance on the tax meaning from these sources.
Jurisdictional Note
Federal tax law governs the casualty loss deduction for federal income tax purposes, and post-2017 limitations are uniform nationally. State income tax treatment of casualty losses varies; some states conform to the federal limitations and others do not, making state tax research essential when the question is state deductibility. In insurance law, casualty is defined by policy language and state insurance regulation, with meaningful variation across jurisdictions.
Encyclopedia Cross-Reference
Itemized Deductions — Casualty and Theft Losses (The Law Mind Tax Encyclopedia)