Definition
In Roman and civil law, an answer or response. The term denotes a formal reply in a legal proceeding — most commonly the response of a witness or party to a question put before a tribunal. As a standalone term, *responsio* simply means "answer," but it appears most frequently in legal literature as part of the maxim *responsio unius non omnino audiatur* — "the answer of one witness shall not be heard at all" — which encodes the Roman law rule requiring corroboration of testimony before a fact can be established.
Why It Matters in Research
*Responsio* is not a term of art in common law systems and will not appear in American or English statutes or case reporters under that label. Researchers encounter it almost exclusively in two contexts: (1) treatises on the Roman or civil law tradition, where it appears in discussions of testimonial evidence and witness corroboration; and (2) early American evidence scholarship that drew on civilian sources to articulate evidentiary principles.
The maxim *responsio unius non omnino audiatur* is the practically significant phrase. Greenleaf's *Treatise on the Law of Evidence* (§ 260) invokes it when discussing the weight of a single uncorroborated witness — a live issue in 19th-century American evidence law. Researchers working in that period should understand that citation to this maxim signals engagement with civil law roots of the corroboration requirement, not a direct application of Roman procedure.
A trap for historical researchers: the corroboration principle the maxim expresses does not translate cleanly into common law doctrine. Common law generally allowed conviction or judgment on the testimony of a single credible witness (with exceptions, such as perjury and treason). When 19th-century writers cite *responsio unius*, they are often arguing by analogy from civilian sources rather than stating binding common law rule. The citation signals a rhetorical or comparative move, not a controlling authority.
Researchers interested in how Roman evidentiary principles entered American legal discourse should trace the chain from Justinian's *Codex* (C. 4.20.9, the source of the one-witness rule) through continental commentators, through Scottish and English equity practice, and finally into treatise writers like Greenleaf and Starkie. *Responsio* as a term marks the entry point of that civilian strand.
Historical Dictionary Support
Burrill's *Law Dictionary* treats *responsio* briefly, defining it as "an answer" and immediately pivoting to the maxim *responsio unius non omnino audiatur*. This is characteristic of how 19th-century common law dictionaries handled Latin civilian terms — acknowledging their existence and doctrinal weight while locating their significance in a particular maxim or rule rather than as freestanding concepts.
Burrill's entry is minimal but accurate. What it omits is context: *responsio* in Roman practice had broader usage than just witness answers and could encompass the responses of legal advisors (*responsa prudentium*), a category of enormous importance in classical Roman law. The *responsa* of jurists like Papinian and Ulpian constituted a recognized source of Roman law under Justinian's *Law of Citations*. Burrill's entry, focused narrowly on the evidentiary maxim, does not gesture toward this larger tradition — a gap that matters if a researcher is trying to understand how the term operates across different periods of Roman legal history.
No other shelf sources cover this term directly. The entry stands as a single-source snapshot, and researchers should supplement it with civilian law references for any substantive Roman law research.
Jurisdictional Note
*Responsio* as a term of art has no independent operation in American common law jurisdictions. Its relevance in U.S. legal research is historical and comparative. Louisiana, with its civil law heritage, is the jurisdiction most likely to surface civilian terminology in operative legal texts, but even there *responsio* does not appear as a term of art in modern practice.