Definition
Jus jurandi forma is a Latin maxim from Roman law meaning, in substance: the form of an oath differs in words but agrees in meaning. The full expression — *jus jurandi forma verbis differt, re convenit* — holds that while oaths may vary in their precise verbal formulation, they share a common essential character: an invocation of divine witness to the truth of a statement or the sincerity of a promise. The maxim recognizes that the binding force of an oath resides not in any particular formula of words but in the underlying act of swearing itself.
In practical legal application, the principle stands for the proposition that minor variations in the language used to administer or take an oath do not vitiate the oath, provided the substance — the solemn appeal to a higher power or to conscience — remains intact.
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Common Confusion
This maxim should not be confused with substantive doctrines governing the *validity* of oaths as a matter of competency or evidence. The maxim addresses formal variation in oath language, not the legal consequences of false swearing (perjury) or the rules governing who may be sworn. Researchers encountering the phrase in older sources sometimes misread it as a general statement about oath-taking procedure, when it is more precisely a canon of construction: differences in verbal form do not create differences in legal effect.
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Why It Matters in Research
This term appears almost exclusively in the Latin-maxim literature and in sources treating Roman law foundations of oath doctrine. Researchers are unlikely to encounter it as a freestanding legal concept in modern common law materials; its practical significance is as a canon of construction invoked when courts or commentators address whether a departure from a prescribed oath formula is fatal to the oath's validity.
The fragment preserved in Black's 2nd edition is truncated — the entry as it appears in the source material breaks off mid-maxim — which is a hazard for any researcher relying on that edition alone. The full maxim, traceable to Roman juristic writing, completes the thought by specifying that the oath must carry the sense that God (or the invoked power) is called as witness. Researchers working in early American or colonial legal materials will find oath-form disputes arising frequently in ecclesiastical, probate, and equity proceedings, where this maxim was occasionally cited to excuse deviations from statutory oath language.
The maxim also appears in the background of debates over affirmations as substitutes for oaths — a recurring issue in Quaker jurisprudence and in constitutional provisions separating oath from affirmation. While the maxim itself does not directly address affirmations, its logic (substance over form) informed arguments that a sincere affirmation satisfied the underlying purpose of an oath.
For corpus researchers: the term indexes poorly in digitized sources because it appears almost always as part of a Latin string rather than as a standalone headword. Search strategies should include variant spellings (*jurandi*, *jurando*) and should look for the fuller phrase *verbis differt, re convenit* to locate the maxim in context.
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Historical Dictionary Support
Black's Law Dictionary (2nd Ed.) is the sole dictionary source available for this entry, and the text as preserved is fragmentary — the entry appears to have been physically cut off, leaving only the opening clause of the maxim and the beginning of its explanatory gloss. What survives confirms the maxim's content and its Roman law provenance, but the truncation means Black's cannot be relied upon here for a complete doctrinal account.
The surrounding entry in Black's 2nd Ed. — which treats *jus Italicum* and Roman provincial law just before pivoting to this maxim — reflects the editorial habit of 19th-century legal dictionaries to collect Latin maxims in sequence under the *jus* headword without extended commentary. This is characteristic of Bouvier and similar contemporaries as well: the maxims are recorded, their Latin text given, but application in common law courts is left largely implicit.
What the historical dictionaries collectively miss is any sustained treatment of how Anglo-American courts actually applied or declined to apply this maxim. The gap between the Roman-law theoretical statement and common law practice is not addressed in the dictionary literature and must be pursued in treatise and case materials directly.
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