Definition
Latin: "description of a person." Designatio personae refers to the identification or description of a specific person — typically a party to a deed, contract, grant, or bequest — by some characteristic, title, office, or relationship rather than (or in addition to) by name. The phrase captures the principle that the identity of a person in a legal instrument is determined by the description used, not merely the name written.
The doctrine operates in two practical contexts:
1. Construction of instruments: When a person is described by role or characteristic (e.g., "my eldest son," "the vicar of St. Andrew's"), the description controls identity. If the name and the description conflict, courts must determine which governs — the named individual or the person who actually fits the description.
2. Exclusion by specification: The maxim attached to the term — designatio unius est exclusio alterius ("the specification of one is the exclusion of another") — extends the doctrine into interpretive canon. When a specific person is named or described, others not named or described are presumed excluded. This is the legal ancestor of the broader expressio unius canon of construction.
Common Confusion
Designatio personae is closely related to but distinct from the general canon expressio unius est exclusio alterius. Expressio unius applies broadly to the enumeration of things, classes, or conditions in a legal instrument or statute. Designatio personae is the narrower, person-specific application of the same logic: the identification of one person excludes others not identified. Researchers should not conflate the two when tracing the interpretive canon through historical sources, as older authorities may use designatio personae in contexts where modern courts would simply invoke expressio unius.
Why It Matters in Research
This term appears most frequently in older equity, property, and succession materials, particularly in cases involving wills, trusts, and grants where a beneficiary or grantee is described by relationship or office rather than name. Researchers working with historical deed and probate records will encounter disputes turning entirely on which aspect of the description — name or role — controls.
Two research traps are worth flagging:
First, the attached maxim (designatio unius est exclusio alterius) is a variant formulation of expressio unius. Historical sources, particularly pre-twentieth century treatises on statutory construction, sometimes cite the designatio form when discussing the exclusion canon. If your research involves tracing that canon's development, you must search both formulations.
Second, Bouvier's entry for this term is a dead reference — it appears to redirect without providing substantive content — and Rapalje & Lawrence similarly offers no independent definition. Black's provides the core working definition and the associated maxim. For historical depth beyond Black's, researchers should look to Coke upon Littleton (the source cited in Black's as Co. Litt. 210) and to early equity treatises on the construction of deeds and wills, where the doctrine was most actively developed.
In the context of gifts and bequests, the doctrine also matters where a testator names a person by office or title that may have changed hands by the time the instrument takes effect — raising the question of whether the gift follows the name or the office. This has generated a distinct line of probate and trust cases that may not surface under searches for the Latin phrase alone.
Historical Dictionary Support
Black's Law Dictionary provides the operative definition — the description of a person or party to a deed or contract — along with the associated maxim in full Latin with translation: "The specifying of one is the exclusion of another, and that which is expressed makes that which is understood to cease," citing Co. Litt. 210. This is the primary historical source for the term's legal usage.
Bouvier's entry redirects without content, offering no independent analysis. Rapalje & Lawrence similarly provides no definition. The absence of substantive entries in two of the three source dictionaries is itself informative: by the time these dictionaries were compiled, designatio personae had become a term of art whose content was considered self-evident or adequately covered elsewhere. Researchers should not interpret the thin dictionary record as evidence of a marginal concept — it was, rather, a well-established doctrine that did not require extended treatment.
The reliance on Coke's authority in Black's places the doctrine firmly in the classical common law tradition of deed construction, where the careful identification of parties was essential to the conveyance's validity and effect.