Definition
A Latin term meaning "of double tongue" or "able to speak two languages." In English legal history, bilinguis describes a jury composed partly of native Englishmen and partly of foreigners, empaneled in cases where one of the parties was an alien. This was the jury's defining characteristic: its mixed national composition was designed to ensure that a foreign litigant received judgment from peers who shared his language and circumstances. The device is more formally known as the jury de medietate linguae — literally, a jury of the half-tongue — of which bilinguis is the adjectival descriptor.
Common Language
Modern common usage (Wiktionary): Double-tongued, deceiving; also, a jury made up partly of natives and partly of foreigners.
Historical common usage (Webster's 1913): Not separately defined; the Latin root bilinguis carried the classical sense of "double-tongued" with a strong connotation of duplicity or deceit — a person who speaks from both sides of the mouth.
The gap here is instructive. In classical Latin, bilinguис carried a moral charge: the double-tongued person was a liar or a dissembler. English law stripped that pejorative sense entirely and repurposed the term as a neutral procedural descriptor — one who can speak two languages, and therefore a jury that speaks, collectively, in two languages. A researcher encountering the word in a non-legal Latin source should not carry the classical meaning into a legal context.
Common Confusion
Bilinguis is frequently used interchangeably with jury de medietate linguae, but the terms are not identical. Bilinguis is the adjectival label for the jury's character; de medietate linguae is the formal name of the procedural institution. Sources may also conflate bilinguis juries with the separate (though related) concept of alien juries or mixed juries in a broader sense. The medietate linguae jury had specific eligibility rules, procedural triggers, and a distinct historical trajectory; bilinguis alone tells you what the jury was, not how it was constituted or when it could be demanded.
Why It Matters in Research
Bilinguis is a gateway term. Researchers who encounter it in older English reports or treatises are almost always looking at a question about the rights of alien parties in litigation — specifically, whether a foreign litigant could demand a half-foreign jury. That right had a long English history stretching from the medieval period through at least the eighteenth century, and the procedural mechanism it describes was abolished in England by statute in the nineteenth century.
Several research traps exist. First, the term appears almost exclusively in older sources; modern legal materials rarely use it, and researchers searching for it in contemporary databases will find little. The productive search is on jury de medietate linguae, which connects to a richer body of case law and commentary. Second, the classical Latin meaning of "double-tongued" as deceitful can mislead researchers scanning Latin-language sources without legal context. Third, Blackstone's treatment at 3 Bl. Comm. 360 is the standard anchor citation used by nearly every source on this term — researchers should go there first for the doctrinal baseline, then trace forward through Stephen's Commentaries (4 Steph. Comm. 422) for the later evolution.
For American researchers: the medietate linguae jury was carried into some early American practice but fell into disuse without the same formal statutory abolition England undertook. Its presence in American sources is sparse and jurisdiction-specific.
Historical Dictionary Support
The historical dictionaries surveyed are in close agreement on the core definition and show little meaningful divergence. Black's (both editions), Bouvier, Rapalje & Lawrence, and Burrill all define bilinguis as "of double language or tongue" and all connect it to the mixed jury for alien parties. The agreement is nearly verbatim across sources, which reflects that these dictionaries were drawing from the same narrow pool of authority — primarily Blackstone and Jacob's Law Dictionary.
Bouvier adds the citation to Plowden (Plowd. 2), giving the term an earlier anchor in the reports. Rapalje & Lawrence is notable for explicitly distinguishing bilinguis from the jury de medietate linguae while acknowledging that the latter is the more precise term — a distinction the other dictionaries make implicitly but do not state as directly.
What the historical dictionaries do not provide: any treatment of the term's procedural mechanics, the conditions under which the right could be invoked, or the term's eventual obsolescence. For that substance, researchers must move from the dictionary entry to the substantive sources those entries cite.
Jurisdictional Note
The bilinguis jury and the underlying de medietate linguae right were English common law institutions. England abolished the right by statute in the nineteenth century. In the United States, the practice was recognized in some early jurisdictions but never uniformly adopted, and it disappeared from American procedure without formal abolition in most states. Researchers should not assume the right existed in any particular American jurisdiction without affirmative evidence.