Definition
A Latin maxim meaning "in double." Used in legal contexts to express the concept of doubling — most commonly in the phrase *damna in duplo*, meaning double damages. The term signals that a penalty, award, or liability is to be measured at twice the standard amount, either by statutory mandate or judicial decree.
Why It Matters in Research
*In duplo* is a phrase researchers are most likely to encounter in historical sources discussing double damages — a remedy with deep roots in Roman and English law that carries forward into modern statutory contexts (treble damages under antitrust law, double damages under certain employment statutes, etc.). When reading older treatises or pleadings that use *in duplo* without elaboration, the surrounding context almost always concerns punitive or statutory multiplication of a damages award.
The phrase itself rarely appears in modern American case law or statutes, which have replaced Latin shorthand with plain-English formulations ("double damages," "twice the amount"). Researchers working in pre-twentieth-century English or American sources, however, may encounter *in duplo* as a standard term of art in discussions of statutory penalties, forfeitures, and punitive multipliers.
The canonical citation in all four source dictionaries — Fleta, lib. 4, c. 10, § 1 — points to *Fleta*, a late thirteenth-century English legal treatise (c. 1290) written in Latin and modeled on Bracton. The Fleta reference anchors *in duplo* firmly in the medieval common law tradition of translating Roman law penalty concepts into English judicial practice. Researchers pursuing the doctrinal history of double damages through to modern statutory multipliers will find *Fleta* a useful starting point for understanding the phrase's pedigree, though the treatise requires specialist access and Latin facility.
Note that *in duplo* is a descriptor of remedy, not of liability. Finding the phrase in a source tells you *how much* was awarded or forfeited, not *why* the underlying obligation arose. Researchers should look separately at the substantive cause of action to understand the basis for triggering the doubled penalty.
Historical Dictionary Support
All four source dictionaries — Black's (both first and second editions), Burrill's, and Bouvier's — give virtually identical entries: the Latin gloss "in double," the illustrative phrase *damna in duplo* (double damages), and the citation to Fleta. There is no meaningful divergence among the sources on meaning or application.
The uniformity is itself informative: *in duplo* was a settled, uncontested term of art by the time these dictionaries were compiled. None of the sources elaborate on when double damages were available, what procedural vehicle triggered them, or how courts calculated the baseline against which doubling applied. Researchers should not expect the dictionary entries themselves to resolve those questions — they function as glosses, not doctrinal guides.
Black's first and second editions reproduce the same content with only minor typographic differences (the second edition corrects "du-plo" from the first edition's hyphenated line-break form, and tidies "dtplo" — an apparent typesetting error — back to "duplo"). Burrill's entry is the most formally structured of the four, explicitly labeling the language as Latin ("Lat."). Bouvier's is the most compressed, dropping the section symbol and abbreviating the Fleta citation.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Damages — Punitive and Statutory Multipliers; Fleta (Treatise)