Definition
A Latin phrase meaning "giving the reason of his knowledge." In Scots law practice, *reddens causam scientiæ* is a formal phrase that historically appeared in witness depositions to introduce the witness's explanation of *how* they came to know what they claim to know — that is, the basis or foundation for their knowledge. The phrase precedes the witness's statement of the grounds upon which their testimony rests.
In practical terms, when a witness in Scottish legal proceedings stated a fact, they were expected to follow with a *reddens causam scientiæ* — a formal declaration explaining the source of their knowledge: whether by personal observation, report from another, inference from documents, and so forth. The phrase thus served as a structural marker in the recorded deposition, signaling the transition from the statement of fact to its evidentiary foundation.
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Why It Matters in Research
Researchers working in pre-modern Scots law sources — particularly printed trial records, state trials, and ecclesiastical court depositions — will encounter this phrase as a standard formulaic marker. It is not a legal doctrine in the modern sense but a procedural formula embedded in the conventions of Scots written deposition practice.
The key navigational point: when this phrase appears in a historical source, everything that follows it (until the next substantive question or topic) is the witness's account of *why they know*, not what they know. Misreading the structure of these depositions — treating the *reddens* passage as the substantive testimony rather than its foundation — can lead to serious mischaracterization of what a witness actually claimed to have witnessed directly versus what they knew by report or inference.
The phrase appears in 2 Howell's *State Trials* (cited by Black's), a key printed source in the Law Mind corpus for early modern English and Scottish criminal procedure. Researchers using Howell should watch for this formula throughout Scottish-origin proceedings reproduced in that collection.
There is no meaningful modern counterpart in common-law jurisdictions. Contemporary evidence law addresses the same underlying concern — the basis of witness knowledge — through the requirement that lay witnesses testify only to matters within their personal knowledge, and through the *foundation* requirements for expert testimony, but neither employs this formula.
Researchers working in comparative legal history connecting Scots civil law procedural traditions to Continental (Roman-canon) notarial and deposition practice will find the *reddens causam scientiæ* useful as a marker of that inheritance. The formula reflects the civilian requirement that depositions be not merely assertions but rationalized accounts — a structural expectation foreign to common-law oral examination practice.
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Historical Dictionary Support
Black's Law Dictionary (2nd Ed.) gives the definition concisely: "Giving the reason of his knowledge. In Scotch practice. A formal phrase used in depositions, preceding the statement of the reason of the witness' knowledge." Black's cites 2 Howell's *State Trials* 715 as authority.
Notably, Black's appends to this entry an unrelated Latin maxim — *Reddere, nil aliud est quam acceptum restituere* ("To render is nothing more than to restore that which has been received"), drawn from Coke on Littleton — which appears to have been placed in sequence due to the shared root word *reddere*, not because it bears on *reddens causam scientiæ* itself. Researchers should not conflate these two entries; the Coke maxim concerns the legal meaning of "render" in property conveyancing contexts and has no bearing on Scots deposition procedure.
The historical dictionaries do not elaborate on the procedural mechanics of how the formula was employed, how it was distinguished from the substantive testimony, or how Scottish courts treated defective or missing *reddens* passages. For deeper treatment, researchers would need to consult Scots institutional writers or the records themselves.
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Jurisdictional Note
This term is specific to historical Scots law procedure and has no operative role in modern Scottish, English, or American legal practice. It surfaces exclusively in primary sources from pre-modern Scottish court proceedings and in collections of historical trials such as Howell's *State Trials*. Researchers encountering it outside a Scots procedural context should treat it as a formulaic borrowing or an archaic citation convention.
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