Nisi prius

Nisi prius (/ˈnaɪsaɪ ˈpraɪəs/) is a historical term in English law. In the nineteenth century, it came to be used to denote generally all legal actions tried before judges of the King's Bench Division and in the early twentieth century for actions tried at assize by a judge given a commission. Used in that way, the term has had no currency since the abolition of assizes in 1971.

Before the reforms of the Judicature Act 1873, civil cases at common law were begun in one of the three courts that sat in Westminster Hall: the Court of Common Pleas, Court of Exchequer and King's Bench. Because of their historical origins, these courts were to some extent in competition, especially as their respective judges and officers lived off the fees deriving from them. Given that travel to London was an onerous burden during the medieval period, however, the Statute of Westminster II provided in 1285 for trial of fact in civil cases at the local assizes. Nisi prius translates as "if not sooner" or "if not before" in addition to "unless first": when the action was started in London, the sheriff was ordered to have the jurors there for trial on a certain day "unless before" (nisi prius) that day the case was heard at assize in the claimant's county. After trial at the assizes, the case could be referred back to the original court, from where there was a possibility of further appeal to the Court of Exchequer Chamber.

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