Definition
To forswear is to swear falsely — to take an oath to something the swearer knows to be untrue. The term carries a broader reach than perjury: forswearing covers any false oath, whether made before a competent legal tribunal or not. A person may be forsworn by lying under oath before an officer without authority to administer it, or on a matter not material to any legal proceeding. Perjury, by contrast, requires a lawful oath before a competent court or officer on a material issue.
The word also carries a second, older sense: to renounce or abjure something by oath — to swear off a thing, a place, or a person. This renunciatory meaning appears in historical property and exile contexts (see forisjurare) and in literary usage, but is largely obsolete in modern American law.
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Common Language
Modern common usage (Wiktionary): To renounce or deny something, especially under oath; also, to commit perjury or break an oath.
Historical common usage (Webster's 1913): To reject or renounce upon oath; hence, to renounce earnestly or determinedly. Also, to deny upon oath; and reflexively (to forswear oneself), to swear falsely.
The gap matters for researchers. In ordinary English, forswear most naturally means to renounce or give something up — "he forswore alcohol." In legal usage, the operative meaning is the opposite emphasis: false swearing, not virtuous abstention. A historical source using forswear in a legal context almost certainly means false oath, not renunciation, unless the document is discussing abjuration of the realm or similar archaic proceedings.
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Common Confusion
FORSWEAR vs. PERJURY: These terms are frequently treated as synonyms in older sources, but they are not interchangeable. Perjury is the narrower, technical offense: a willful false statement made under a lawful oath, before a competent tribunal, on a matter material to the proceeding. Forswearing requires none of those limiting conditions — a false oath before an incompetent officer, or on an immaterial point, may constitute forswearing without amounting to perjury. Bouvier and Burrill both flag this distinction explicitly. Researchers encountering forsworn or forswear in historical pleadings, defamation cases, or criminal indictments should not assume perjury is alleged.
FORSWEAR vs. ABJURE: In medieval and early modern English law, forswear and abjure overlapped considerably, both being used for formal renunciations under oath (abjuration of the realm, for instance). By the eighteenth century, legal dictionaries were treating the renunciatory sense as secondary or archaic. Modern usage has abandoned it almost entirely in legal contexts.
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Why It Matters in Research
The forswear/perjury distinction is a practical trap in historical sources. Nineteenth-century defamation cases frequently turned on whether calling someone "forsworn" was actionable slander per se. Bouvier notes explicitly that saying a man is forsworn may or may not be slander, depending on context — because forswearing, unlike perjury, does not necessarily impute a crime punishable by law (since the false oath may have been made before an incompetent tribunal). Researchers tracing slander doctrine in early American and English cases need to track which term is used and what tribunal is implied.
In criminal law research, indictments and charge sheets from the eighteenth and early nineteenth centuries may use forswear where modern drafters would say perjury or false swearing. The distinction mattered for pleading: an indictment charging perjury required specific averments of competent tribunal, lawful oath, and materiality. An allegation of forswearing carried no such formal requirements but also may not have stated a cognizable statutory offense.
The abjuration sense of forswear will appear in property law sources dealing with outlawry and abjuration of the realm — contexts where a person forswore (renounced) England or a particular jurisdiction by oath as a condition of avoiding execution. Burrill cross-references forisjurare for this meaning. Researchers should consult that entry when the term appears in medieval or early modern land title chains or exile proceedings.
Corpus researchers should also note that forswear appears in equity proceedings related to oath-based discovery. The distinction between forswearing and technical perjury was sometimes invoked to argue that a false answer in equity (before a master or commissioner whose authority was disputed) was not perjury — a defense that courts treated with varying degrees of patience.
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Historical Dictionary Support
The historical dictionaries converge on the core distinction from forswear to perjury with unusual consistency. Burrill (citing Cro. Jac. 190 and 2 Johns. R. 10) and Bouvier both note that forswearing does not ex vi termini — by the force of the term itself — import perjury. Anderson is concise: "Does not necessarily import perjury. One may swear to what is not true before an officer not qualified to administer an oath." Black's (both editions) states the distinction cleanly: forswear is wider in scope because perjury requires a competent tribunal and a material issue.
Where the sources diverge slightly is in emphasis. Burrill gives the abjuration/renunciation meaning first, reflecting an older organizing principle that takes the Latin forisjurare as the root concept. Black's leads with the false-swearing meaning, reflecting the more practically relevant modern usage. Bouvier develops the defamation angle most fully, gesturing toward the slander cases without resolving them definitively — appropriate for a law dictionary entry but a reminder that the case law must be consulted independently.
None of the historical dictionaries fully addresses the statutory dimension: most American jurisdictions eventually codified false swearing as a distinct offense, partially collapsing the common law distinction between forswearing and perjury. Modern penal codes rarely use the word forswear at all.
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Jurisdictional Note
The practical significance of the forswear/perjury distinction varied across American jurisdictions depending on how broadly state courts defined perjury and whether false swearing before incompetent officers was separately criminalized. English common law sources (Cro. Jac., Barn. & A.) inform the doctrine but should not be assumed to control in any American jurisdiction without independent verification. Modern American statutes have largely displaced the common law framework.
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Encyclopedia Cross-Reference
See Law Mind Encyclopedia — Perjury (for the technical elements distinguishing perjury from broader false swearing); Oath (for the competency requirements that determine when false swearing may rise to perjury).
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