Definition
A judge assigned or appointed by a Roman magistrate — specifically the praetor — to hear and decide a particular cause. In the classical Roman procedural system, the praetor did not himself conduct the full trial. Instead, after the parties appeared before him in the preliminary stage (the *in iure* phase) and the legal issues were framed, the praetor would appoint a private citizen — the *judex datus* — to receive the evidence, evaluate the facts, and render judgment. The *judex datus* was thus a delegated adjudicator rather than a permanent judicial officer: appointed for one case, bound by the formula issued by the praetor, and without independent authority to reshape the legal question he was given to resolve.
Common Confusion
*Judex datus* is occasionally conflated with *judex selectus* (a judge chosen from a panel) or with *arbiter* (a figure appointed with broader discretionary authority to decide according to equity rather than strict formula). The distinctions matter in historical research: an *arbiter* had wider latitude than a *judex datus*, who was bound to decide within the precise terms of the praetorian formula. Conflating them distorts both the constraining role of the formula and the comparative significance of equitable discretion in Roman procedure.
Why It Matters in Research
This is a term of Roman law that surfaces in historical legal literature primarily as explanatory background for understanding the structural separation, unique to Roman civil procedure, between the *in iure* (law-defining) phase before the magistrate and the *apud judicem* (fact-deciding) phase before the appointed judge. Researchers encounter *judex datus* most often in treatises on Roman law, in comparative legal history, and in early common law scholarship that drew on Roman procedure to theorize about the role of judges and juries.
The principal research trap is assuming that *judex datus* describes anything resembling a modern appointed judge. The *judex datus* had no general or continuing judicial authority. He was closer to what modern procedure might call a special master or referee — a person empowered to decide a specific dispute on specifically framed terms — than to an Article III judge or a professional magistrate. Sources that translate *judex datus* simply as "appointed judge" without this procedural context can mislead readers into importing modern assumptions about judicial independence and scope.
The term also appears in discussions of *judex* more broadly. Historical sources frequently treat *judex datus* as a subcategory within a family of Roman judicial roles, and researchers working through entries on *judex*, *arbiter*, or Roman civil procedure will encounter it in that comparative context. Note that Black's includes an appended maxim — *judex debet judicare secundum allegata et probata* (the judge ought to decide according to the allegations and the proofs) — in what appears to be a typographical conflation of adjacent entries. That maxim is a separate principle, not a qualification of *judex datus* specifically, and should be treated as an independent entry in research.
Historical Dictionary Support
Black's Law Dictionary and Burrill's Law Dictionary are in close agreement on this term, both defining it as a judge given, assigned, or appointed by the praetor to try a cause. Burrill adds the qualifier "in old Roman law," which is the more precise framing: the *judex datus* is a feature of the classical *formulary* system of Roman civil procedure, and it had been substantially displaced before Justinian's consolidations in the sixth century. Neither source elaborates on the procedural mechanics that give the term its meaning — the formula system, the distinction between the *in iure* and *apud judicem* phases, or the relationship between the *judex datus* and other Roman adjudicatory figures such as the *arbiter* or the *recuperatores*. Researchers seeking that depth must look beyond dictionary sources to Gaius's *Institutes* or Justinian's *Digest*, where the structural role of the delegated judge is treated at length.
Neither dictionary entry is wrong; both are simply incomplete in a way that reflects how Roman law terms were handled in nineteenth-century Anglo-American legal dictionaries — as glossary items rather than substantive explanations.
Jurisdictional Note
This is a term of Roman law with no direct counterpart in modern common law jurisdictions. It appears in American and English legal literature solely in historical, comparative, and theoretical contexts. It carries no operative legal meaning in any current jurisdiction.