Definition
The killing of one's brother or sister. As a legal term, fratricide functions both as a label for the act itself and as a designation for the person who commits it — that is, the killer of a sibling. The term appears in criminal law primarily as a descriptive category of homicide distinguished by its familial relationship, not as a separate offense. No modern common law jurisdiction treats fratricide as a distinct statutory crime; the act is prosecuted under general homicide statutes, with the familial relationship potentially affecting sentencing, motive analysis, or — in some civil law traditions — inheritance consequences.
Common Language
Modern common usage (Wiktionary): The killing of one's brother or sister; also the unintentional killing of a comrade in arms (military usage); also a technical term in weapons systems for interference between MIRV warheads.
Historical common usage (Webster's 1913): The act of one who murders or kills his own brother; also, the person who commits such an act. Webster's 1913 confined the term to the killing of a brother only, excluding sisters.
The legal dictionaries corrected Webster's gender limitation early: Black's, Rapalje & Lawrence, and Bouvier's all explicitly extended the definition to cover the killing of a brother or sister. A researcher reading Webster's 1913 in isolation would find a narrower term than the one operative in legal sources from the same period. The military and weapons-systems senses carried by modern common usage have no legal significance in the criminal or civil law contexts where fratricide appears in historical sources.
Common Confusion
Fratricide is one of a family of relationship-specific homicide terms — alongside parricide (killing of a parent or close relative), matricide (killing of a mother), patricide (killing of a father), and uxoricide (killing of a wife) — that researchers sometimes conflate or use interchangeably. These are descriptive categories, not separate offenses at common law. The broader term parricide is occasionally used in historical sources to encompass fratricide and other intrafamilial killings, which can cause indexing confusion in older treatises and digests. Anderson's Dictionary of Law handles fratricide by simple cross-reference to HOMICIDE, signaling that the legal operative category is always the genus, not the species.
Why It Matters in Research
Fratricide is taxonomic, not operative. A researcher searching for fratricide in statutes, indictments, or case law will find very little, because the act is charged as murder or manslaughter, full stop. The term's legal utility is primarily in treatises, legal encyclopedias, and civil law materials where relationship-specific homicide categories carry independent weight — particularly in succession law, where killing a sibling may affect inheritance rights under slayer rules or civil law forfeiture doctrines.
Historical sources indexed under HOMICIDE rather than FRATRICIDE: Anderson's cross-reference practice reflects a broader indexing pattern. Nineteenth-century digests and encyclopedias frequently subsumed fratricide within homicide entries. Researchers working in older corpus materials should not treat absence of a standalone fratricide entry as evidence the issue was unaddressed.
Civil law relevance: In civil law jurisdictions and in the Roman law tradition from which many of these terms derive, fratricide carried specific legal consequences beyond criminal punishment — including forfeiture of inheritance and, in some systems, aggravated penalties. English common law did not adopt aggravated penalties for intrafamilial homicide, but researchers working in Louisiana, Quebec, or comparative law contexts will find the term doing more legal work than it does in common law sources.
Gender of the victim in historical sources: Webster's 1913 limited fratricide to the killing of a brother. Legal dictionaries of the same era were more inclusive. This divergence matters when interpreting non-legal historical documents — a newspaper account or coroner's report using "fratricide" in the Webster's sense may not intend to describe the killing of a sister, even if the legal definition would cover it.
Historical Dictionary Support
The five source dictionaries are in near-complete agreement, which is itself informative: fratricide attracted no doctrinal controversy and generated no competing definitions. Black's (both editions) and Bouvier's offer identical formulations covering both the act and the actor, and both extend the definition to sisters. Rapalje & Lawrence is slightly narrower in phrasing — defining only the act, not the actor — but consistent in substance. Anderson's dispensed with a standalone definition entirely, treating fratricide as a subtype of homicide not requiring separate elaboration.
What the historical dictionaries do not address: none of the source dictionaries discuss inheritance consequences, aggravated criminal penalties, or the civil law tradition underlying the term. They also do not note the absence of fratricide as a distinct statutory offense. For researchers, this silence is meaningful — the dictionaries confirm the term's definitional content while leaving its legal consequences entirely to the homicide and succession entries.
Jurisdictional Note
In common law jurisdictions, fratricide has no independent statutory existence and is prosecuted under general homicide law. In civil law systems, particularly those derived from Roman law or the Napoleonic tradition, the familial relationship in an intrafamilial killing may trigger specific succession consequences under slayer or forfeiture rules. Louisiana researchers should consult both civil and criminal law sources.