Definition
A complainant is a party who initiates a legal proceeding or formally asserts a grievance before a court or other legal body. The term carries different weight depending on context:
1. In equity practice: The party who files a bill of complaint and seeks equitable relief — the functional equivalent of a plaintiff at common law. This is the term's primary historical legal meaning.
2. In criminal proceedings: The alleged victim or aggrieved party who reports an offense, prompting prosecution. The complainant in this sense is not the prosecuting party (the state is), but the individual whose harm underlies the charge.
3. In administrative and quasi-judicial proceedings: The party who initiates a complaint before a regulatory body, tribunal, or agency.
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Common Language
Modern common usage (Wiktionary): One who makes complaint; the party bringing a civil lawsuit; an alleged victim in a criminal investigation or trial.
Historical common usage (Webster's 1913): One who makes complaint; the party suing in equity, answering to the plaintiff at common law.
The common meaning tracks the legal meaning more closely here than with many legal terms, but the gap is meaningful in one direction: ordinary usage treats complainant and plaintiff as interchangeable, and uses complainant loosely for any person who complains. Legal usage is more precise. In equity, complainant was the technically correct designation; plaintiff was a common-law term. In criminal proceedings, complainant identifies the alleged victim — not the prosecuting party — a distinction that matters significantly in criminal research.
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Common Confusion
Complainant vs. Plaintiff: These terms overlap but are not synonymous. Historically, complainant was the correct label in equity; plaintiff belonged to common law courts. The merger of law and equity in most American jurisdictions has blurred this line, and plaintiff now dominates both contexts. Researchers encountering complainant in pre-merger equity records should not assume it is simply an older word for plaintiff — it signals a specific procedural posture and body of equity doctrine.
Complainant vs. Petitioner: In some courts and administrative proceedings, petitioner performs a similar function to complainant. The choice of term often signals the nature of the proceeding: complaint-based actions vs. petition-based actions. Do not conflate them across jurisdictional or procedural boundaries.
Complainant vs. Victim: In criminal law, complainant is sometimes used as a more neutral, legally precise alternative to victim — particularly before conviction, when victim status is not yet established. Some jurisdictions and courts use the terms differently by rule or convention.
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Why It Matters in Research
The term's meaning shifts across three fault lines: time period, court type, and proceeding type.
Time period matters most. In sources predating the merger of law and equity (mid-19th century federally; varying by state), complainant almost always signals an equity proceeding. Finding complainant in a case caption or pleading heading is itself a clue about jurisdiction, procedure, and available remedies. Researchers working with colonial, early republic, or antebellum materials need to read complainant as an equity marker, not just a synonym for plaintiff.
Court-type variation persists into the modern era. Some states retained separate equity courts or chancery divisions well into the 20th century. Louisiana and Delaware are notable examples. In those jurisdictions, the equity-era usage of complainant survived longer in practice.
In criminal law research, the rise of complainant as a term for the alleged victim is a relatively modern development, accelerated by victim-rights movements and evidentiary reforms affecting how alleged victims are identified and treated in the record. Historical criminal records rarely used complainant in this sense; the term there would more often have been prosecutor, informant, or simply the name of the complaining witness.
Administrative law adds a third layer. Agencies, boards, and tribunals often define complainant by rule, and that definition may be narrower or broader than either the equity or criminal meaning. Always check the governing statute or procedural rules when researching agency complainants.
Corpus navigation tip: In Law Mind sources, complainant will cluster most heavily in equity practice materials, chancery procedure guides, and older form books. Criminal usage will appear in procedural treatises and victim-rights materials. Do not run a search on complainant expecting uniform results — filter by era and court type first.
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Historical Dictionary Support
The five source dictionaries agree on the core meaning: complainant is the equity-court equivalent of the common-law plaintiff. All five make this equation explicitly. Burrill adds the Latin querens — a useful link for researchers working in Latin-language records or early English sources, where the querens was the complaining party. Rapalje & Lawrence extend the term usefully to cover the initiation of a prosecution, suggesting the criminal-law sense was recognized even in 19th-century usage.
Where the historical dictionaries fall short: none of them address the modern criminal-law usage of complainant as alleged victim, nor do they anticipate administrative-law usage. Their framing is almost entirely equity-procedural. Researchers who rely solely on these definitions will miss how the term has evolved in criminal and regulatory contexts over the 20th century. The historical dictionaries are reliable guides to historical equity practice; they are not guides to how the term functions today in criminal courts or before agencies.
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Jurisdictional Note
States that retained separate equity courts or chancery divisions — including Delaware and historically New Jersey — continued using complainant in its strict equity sense well after federal merger. In states where law and equity merged earlier or more completely, plaintiff displaced complainant faster. Criminal-law usage of complainant for alleged victims varies by jurisdiction and is shaped in part by local victim-rights statutes and court rules.
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Encyclopedia Cross-Reference
Law Mind Encyclopedia — Civil Procedure (equity pleading and bill of complaint)
Law Mind Encyclopedia — Criminal Procedure (complaining witness; victim identification)
Law Mind Encyclopedia — Equity Practice (chancery parties and procedure)
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