Definition
AND NISI PRIUS (Latin: "and unless before") is a phrase designating a class of English circuit court sessions — more fully described as commissions of assize and nisi prius — in which royal commissioners, styled judges of assize, traveled the counties of England twice yearly to try disputed questions of fact before local juries. The sessions bore the "nisi prius" label because cases were originally directed to be tried at Westminster "unless before" (nisi prius) that date the justices arrived in the county where the facts arose, allowing trial closer to home. Over time the phrase contracted into a general term for the trial courts sitting on circuit, as distinguished from the superior courts at Westminster Hall where the same cases had been commenced.
The full expression "assize and nisi prius" captures the two-fold commission these judges carried: authority to hold formal assizes (including criminal business and the grand assize) and authority to try the civil issues sent down from Westminster. "And nisi prius" in practice often appears as a shorthand for the civil branch of that combined jurisdiction.
Common Confusion
AND NISI PRIUS is frequently encountered in older sources as a near-synonym for "assize" or simply for any circuit sitting, but the terms are not identical. An assize in the strict sense included criminal jurisdiction and certain real property proceedings; nisi prius jurisdiction was specifically the trial of civil issues of fact already framed in a superior court. A court described only as a "nisi prius court" had no general criminal commission. Researchers who treat assize, nisi prius, and circuit court as interchangeable will misread the scope of a historical tribunal's authority.
Why It Matters in Research
This term appears almost exclusively in English legal materials predating the Judicature Acts of 1873–75, which reorganized the English superior courts and effectively abolished the separate assize-and-nisi-prius machinery as a distinct constitutional structure. Researchers working with pre-1875 English pleading records, writs, or circuit reports will encounter the phrase in procedural headings and in treatise discussions of how cases moved from Westminster to county trial. Three research traps deserve attention.
First, the truncated Latin. Primary sources frequently print only "nisi prius" where the full phrase is "assize and nisi prius." A researcher seeing a bare "nisi prius" reference must determine from context whether it means the circuit commission, the venue rule embedded in a writ, or — in American usage — any trial court of general jurisdiction. American courts and treatise writers adopted "nisi prius" as a general label for trial-level courts well into the nineteenth century, a usage with no English counterpart.
Second, the commissioners' dual authority. Because the same judges held both assize and nisi prius commissions, a single circuit volume may contain criminal assize business and civil nisi prius business side by side. Burrill's entry signals this by noting the commissioners were called "judges of assise, (or of assise and nisi prius)," reflecting that contemporaries used both formulations. Cataloging errors in older reports sometimes fold criminal assize proceedings under "nisi prius" headings and vice versa.
Third, frequency of sitting. Burrill notes the judges were sent "twice in every year." This semi-annual rhythm governed when cases could actually be tried, which matters for understanding continuances, delay, and the costs of litigation in the period. Procedural arguments in pre-1875 English cases often turn on which circuit sitting a case was or was not reached at.
Historical Dictionary Support
Burrill draws on Stephens's Commentaries (3 Steph. Com. 421–422) for the structural description of the commission, characterizing the commissioners as royal agents sent "on circuits all round the kingdom." The entry is reliable as far as it goes but is cut short in the surviving text. Blackstone's Commentaries (Book III, Chapter 21) provides the more complete contemporary account, explaining both the historical derivation of the nisi prius clause from a writ of venire facias and the practical consolidation of assize and nisi prius authority in the same judges. Historical dictionaries uniformly treat this as a term of English procedural art; none of the standard American legal dictionaries (Bouvier, Black) gives AND NISI PRIUS as a standalone headword, confirming its status as an English term of practice that American sources absorbed under the simpler "nisi prius" heading. Researchers relying only on American historical dictionaries will not find this compound phrase directly defined.
Jurisdictional Note
The commission of assize and nisi prius was an English institution without a direct American structural equivalent. American jurisdictions adopted the term "nisi prius" as a descriptor for trial courts generally, but never the assize-commission framework. Scottish, Irish, and Welsh circuit arrangements differed from the English model in important respects; care is needed when comparing circuit materials across the British Isles.