Definition
A Latin phrase meaning "in the passage over" or "on the voyage over." Used in admiralty and maritime law to describe goods, persons, or vessels that are in the course of a sea voyage — specifically, in transit across a body of water. The phrase identifies a temporal and spatial status: the subject is neither at the port of departure nor at the port of destination, but actively mid-crossing.
Why It Matters in Research
This term appears almost exclusively in admiralty law contexts, particularly in prize law and the law of contraband, where the status of cargo or persons at the precise moment of seizure or capture could determine legal rights and obligations. A vessel or cargo "in trajectu" occupied a legally significant moment — rights of capture, salvage, insurance claims, and duties of neutral parties could all turn on whether a voyage was still in progress.
Researchers working in admiralty sources from the late 18th and early 19th centuries will encounter this phrase in the context of British prize court decisions, where Sir William Scott (Lord Stowell) deployed it with precision. The canonical reference across all four source dictionaries is The Daifjee (also spelled with minor variations across editions), decided in the High Court of Admiralty, reported at 3 C. Rob. Adm. Note that Black's 1st edition cites "3 C. Rob. Adm. 141" while Black's 2nd edition gives "8 C. Rob. Adm. 141" — a discrepancy likely attributable to a typographical error in one edition. Burrill's citation of "3 Rob. Adm. R. 141" aligns with the first edition of Black's and is the more reliable reference. Researchers should verify against the Reports of Cases Argued and Determined in the High Court of Admiralty (Christopher Robinson's Reports) directly.
The phrase should not be confused with the closely related in transitu (during transit, or during removal from one place to another), which Bouvier's treats as a separate entry and links explicitly to the doctrine of stoppage in transitu in commercial and mercantile law. The two phrases overlap conceptually — both describe a subject in motion between two points — but in trajectu carries a specifically maritime and voyage-based meaning, while in transitu has broader application across land and sea carriage. Researchers navigating 19th-century commercial law sources may encounter in transitu where admiralty sources would use in trajectu.
Historical Dictionary Support
All four source dictionaries are in substantial agreement on the core definition: "in the passage over; on the voyage over." The consistency across Black's (both editions), Burrill's, and Bouvier's reflects that this was a settled term of art with an uncontested meaning, not a phrase subject to doctrinal dispute.
Burrill's is the most complete of the four, citing the case and judge by name (Sir William Scott, The Daifjee, 3 Rob. Adm. R. 141), which is useful for identifying the authoritative source. Bouvier's is notable for immediately cross-referencing in transitu and directing the reader to stoppage in transitu — a practical acknowledgment that researchers looking up one phrase may need the other.
The discrepancy in volume number between the two Black's editions (3 versus 8) is a textual artifact that should prompt caution. Neither edition provides explanatory commentary beyond the definition and citation, suggesting the compilers treated the phrase as sufficiently clear to need no elaboration.
Historical sources do not address the phrase's use outside prize law or its application in insurance contexts, where the question of whether cargo was in trajectu at the moment of loss could affect underwriting liability. Researchers working on marine insurance history will need to supplement these dictionary sources with treatise literature.
Jurisdictional Note
The term derives primarily from British admiralty practice and appears most frequently in English prize court reports. American admiralty courts, drawing on the same body of maritime law, would have recognized the concept, but the phrase itself is rarely a term of art in American judicial opinions. Researchers in U.S. admiralty sources are more likely to encounter in transitu or plain-English equivalents.