Definition
Non prosequitur (abbreviated "non pros.") is a Latin phrase meaning "he does not prosecute." It refers to a judgment entered against a plaintiff who fails to take required procedural steps within the time prescribed by court rules or practice. When a plaintiff neglects to advance the case as required — failing to appear, file necessary papers, or otherwise pursue the action on schedule — the defendant may move for entry of a non prosequitur judgment. The effect is a judgment against the plaintiff, treating the failure to prosecute as a forfeiture of the action.
Non prosequitur is a procedural sanction, not a ruling on the merits. It reflects the court's insistence that plaintiffs who initiate litigation must actively continue it.
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Common Language
Modern common usage (Wiktionary): "A judgement entered against the plaintiff in a suit where he/she fails to appear to prosecute."
Historical common usage (Webster's 1913): "A judgment entered against the plaintiff in a suit where he does not appear to prosecute. See Nolle prosequi."
The common definitions capture the basic concept accurately, but Webster's cross-reference to nolle prosequi is a navigational trap. Non prosequitur and nolle prosequi are distinct procedures with opposite parties and different contexts. Conflating the two — as even Webster's 1913 invites — is one of the more persistent errors researchers encounter in older materials.
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Common Confusion
Non prosequitur is frequently confused with nolle prosequi. The confusion is understandable: both are Latin dismissal-related terms, both result in a case not proceeding, and older sources sometimes use them loosely. The distinctions are fundamental. Non prosequitur is entered against a plaintiff in a civil action who fails to prosecute; it is a sanction imposed by the defendant's motion or court action for plaintiff's neglect. Nolle prosequi is a voluntary entry by a prosecutor in a criminal matter (or plaintiff in some civil proceedings) indicating willingness to drop the case — it is an affirmative choice, not a penalty for inaction. Additionally, non prosequitur leaves the matter potentially revivable depending on court rules, while nolle prosequi carries its own distinct revival implications. Researchers working in historical civil procedure records should treat any source that blurs this distinction with caution.
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Why It Matters in Research
Non prosequitur belongs to the procedural vocabulary of common-law pleading and is primarily a historical term. Its practical importance peaked in the era of formal common-law practice — roughly through the nineteenth century — before modern codes of civil procedure, particularly those modeled on the Field Code and later the Federal Rules of Civil Procedure, largely replaced it with dismissal for failure to prosecute (now Rule 41(b) in federal practice and equivalent provisions in state codes).
Researchers working in pre-twentieth-century case law, equity practice records, or historical court documents will encounter non pros. entries regularly. In those materials, the abbreviation "non pros." appears in docket books, writs, and court minutes without expansion; knowing the full term and its procedural context is essential to accurate interpretation.
A key research trap: because modern courts and codes replaced non prosequitur with statutory dismissal mechanisms, the term largely disappears from twentieth-century sources. A researcher finding no modern hits for "non prosequitur" should not conclude it was rare — it was simply renamed and absorbed. The functional successor in federal practice is involuntary dismissal under Rule 41(b) for failure to prosecute.
Both editions of Black's Law Dictionary reproduce nearly identical definitions, suggesting the term was already being treated as settled historical material rather than evolving doctrine by the time of the second edition. Neither edition addresses the transition to code pleading or flags the modern successor rule, which limits their usefulness for tracing the term forward in time.
The encyclopedia entries flagged as matches — covering non-solicitation, non-disclosure, and non-compete agreements — share only the prefix "non" and are not substantively related to non prosequitur. Researchers should not follow those cross-references.
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Historical Dictionary Support
Both Black's editions offer consistent, brief definitions that correctly identify the essential mechanism: plaintiff's neglect to take required steps within court-prescribed time, defendant's right to move for the judgment, and the Latin meaning ("does not follow up his suit"). The entries are in agreement and neither adds to the other in any meaningful way.
What the historical dictionaries do not address: the distinction between non prosequitur and dismissal for want of prosecution under code pleading; the effect of the judgment (whether it bars a new action or merely the current one); and procedural variations across jurisdictions in the common-law era. They also do not flag the nolle prosequi confusion, which Webster's 1913 actively compounds.
The phrase "does not follow up his suit as he ought to do" in both Black's editions captures the equitable logic well — the court treats the plaintiff's inaction as an implicit concession that the suit should not continue.
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Jurisdictional Note
Non prosequitur as a formal judgment is largely obsolete in modern American practice, having been displaced by statutory and rule-based dismissal mechanisms. Some states with older procedural codes or strong common-law traditions retained non pros. terminology longer than others. Researchers working in English common-law sources will encounter it in its original procedural context, where it operated as a well-defined common-law judgment form.
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