Definition
Latin: "in defending himself." A term of the common law describing homicide committed in self-defense — specifically, the act of killing another person while defending one's own life or person from an imminent threat. Homicide se defendendo was historically classified as excusable homicide, distinguishing it from justifiable homicide on one side and felonious homicide on the other.
Under the traditional common law framework, se defendendo applied in a narrow factual situation: a person, without fault in provoking the encounter, retreated as far as possible and, finding no further means of escape, killed the attacker in order to preserve their own life. The excusable classification meant the killer was not wholly innocent — hence the older requirement of forfeiture of goods in some periods — but was nonetheless spared criminal punishment.
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Common Language
Modern common usage (Wiktionary): A plea of self-defense.
Historical common usage (Webster's 1913): No entry recorded.
The Wiktionary gloss is accurate as far as it goes but collapses an important distinction. In legal history, se defendendo was not simply synonymous with self-defense as a general defense concept. It was a specific category within the taxonomy of homicide — excusable rather than justifiable — with procedural and moral consequences that differed meaningfully from other forms of self-defense. Using the term as a loose synonym for "self-defense plea" obscures those distinctions, which matter considerably when reading older criminal law authorities.
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Common Confusion
Se defendendo is frequently conflated with justifiable homicide, but the two occupied distinct positions in the classical common law scheme. Justifiable homicide — such as killing in execution of a lawful sentence or in suppression of a riot — carried no legal stigma and historically required no forfeiture. Se defendendo was excusable, meaning the law treated the killing as wrongful in some technical sense even while declining to punish it. The actor was understood to have taken a life under necessity but was not fully absolved in the manner of one acting in the public interest. This distinction largely collapsed in modern American and English law, where self-defense is treated as a full justification rather than a mere excuse in most jurisdictions, but it remains significant when interpreting historical sources.
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Why It Matters in Research
Researchers working in pre-twentieth-century criminal law materials will encounter se defendendo frequently, particularly in treatises on homicide classification. The term signals a specific doctrinal location: excusable homicide, not justifiable homicide, and decidedly not felonious homicide. Reading it as a generic synonym for self-defense will cause misinterpretation of older authorities that carefully maintained these categorical distinctions.
The duty-to-retreat requirement is historically embedded in se defendendo in a way it is not in all forms of self-defense. Classical se defendendo required the defender to have retreated to the wall — that is, exhausted all avenues of escape — before killing. Modern stand-your-ground statutes and the erosion of the retreat requirement in many American jurisdictions mean that contemporary self-defense law has moved well beyond the se defendendo framework, even where courts and commentators still invoke the underlying concept. A researcher tracking the evolution of the retreat doctrine will find se defendendo at the historical root of that debate.
Burrill's cross-reference to Fleta is a useful signal: the term's doctrinal lineage runs deep into medieval English law, and researchers working on the history of the law of homicide should expect to find it in early treatise sources such as Bracton and Fleta before encountering it in later digests. Rapalje & Lawrence's terse cross-reference to "Homicide, 23" reflects the term's function in nineteenth-century practice: it was understood primarily as a sub-category of homicide doctrine rather than as a freestanding defense concept.
The forfeiture consequence attached to se defendendo in early English law — the killer's goods could be forfeited to the Crown even upon a finding of excusable homicide — had been largely abolished by statute by the time American law developed, but its ghost persists in older discussions of the moral distinction between excusable and justifiable killing. Researchers should not assume American sources track English sources on this point without verification.
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Historical Dictionary Support
The four source dictionaries converge on the core meaning without significant divergence: se defendendo means "in defending himself" and describes excusable homicide committed in self-defense. Black's first and second editions are nearly identical, suggesting the term's doctrinal content was stable and uncontested by the late nineteenth century.
Burrill is the most substantive of the four, citing Fleta and providing the Law French equivalent (soy defendaunt), which is useful for researchers working in medieval or early modern English legal records where the Latin and French forms appear interchangeably. The Law French form may appear in Year Book materials and early plea rolls where Burrill's gloss aids identification.
Rapalje & Lawrence's bare cross-reference reflects a common nineteenth-century dictionary practice of consolidating homicide sub-categories under a single main entry. Researchers using that dictionary should follow the cross-reference rather than relying on the se defendendo stub.
What the historical dictionaries collectively omit is any treatment of the doctrinal evolution away from the excusable/justifiable distinction, the abolition of forfeiture consequences, and the emergence of modern self-defense doctrine. For those developments, researchers must move beyond the dictionary shelf to criminal law treatises and statutory history.
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Jurisdictional Note
The excusable/justifiable homicide distinction that gives se defendendo its historical significance has been substantially flattened in modern American jurisdictions, most of which treat self-defense as a complete justification. The practical doctrinal freight the term carried — including the retreat requirement and the forfeiture consequence — varies considerably across modern state law and is largely absent from contemporary statutes that use the term "self-defense" without reference to the older taxonomy.
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