Definition
Ex rel. is an abbreviation of the Latin phrase ex relatione, meaning "on the relation of" or "upon the information of." It appears in the formal title of a legal proceeding to identify the real party in interest — the relator — on whose information or complaint the action is brought, even though the nominal plaintiff is a government entity or public officer.
The construction follows this pattern: the government or official party is named first, followed by "ex rel.," followed by the private individual whose grievance drives the suit. For example: State ex rel. Smith v. Jones. Here, the State is the nominal plaintiff, but Smith is the relator — the person whose complaint prompted the action and whose interests the suit is meant to vindicate.
Ex rel. proceedings arise most commonly in three contexts:
1. Quo warranto and mandamus actions, where a private party seeks to compel or challenge government action through a state attorney general or other official who nominally brings the suit.
2. False Claims Act litigation (federal), where a private whistleblower (the relator) files suit on behalf of the United States government against parties alleged to have defrauded the federal government.
3. Equity proceedings to abate public nuisances, historically brought by the attorney general on the information of affected private parties.
Common Confusion
Ex rel. is sometimes confused with ex parte, another Latin phrase appearing in case titles. They signal opposite things. Ex parte means the proceeding involves only one side — no opposing party has been named or notified. Ex rel. means a named private party stands behind the nominal government plaintiff. A case titled "In re Smith" or "Ex parte Smith" involves Smith as the sole or primary party; a case titled "State ex rel. Smith v. Jones" involves the state as nominal plaintiff, Smith as the real movant behind it, and Jones as the defendant. Conflating these in historical research will send a researcher to entirely the wrong procedural framework.
Why It Matters in Research
The abbreviation is deceptively small but carries significant procedural weight. Researchers must understand that the nominal plaintiff in an ex rel. case is not the party whose rights are ultimately at stake. When searching historical case law or digests, the relator's name may or may not be indexed — older reporters and digest systems varied in whether they indexed under the government entity's name, the relator's name, or both. A researcher who searches only for "State v. Jones" may miss "State ex rel. Smith v. Jones" as the operative case.
In federal False Claims Act qui tam litigation — the most common modern context for ex rel. — the case is filed under seal initially, and the United States decides whether to intervene. The relator proceeds in the government's name but may have independent rights to a portion of any recovery. Understanding ex rel. in this context means understanding the entire qui tam procedural structure, not just the caption.
Historically, ex rel. was the standard mechanism for private enforcement of public rights before modern standing doctrine and public-interest litigation developed. Many significant equity cases from the 19th century addressing public nuisance, corporate charters, and public officer misconduct are captioned this way. Researchers analyzing pre-20th century public law disputes should expect this framing routinely.
Jurisdictional variation matters here: some states require the attorney general's name in the caption; others permit or require the relevant public officer; still others have moved to modern procedural formats that drop the ex rel. construction in favor of direct private standing. When working with state court records across time periods, the absence of ex rel. does not mean the underlying relator structure has disappeared — it may simply have been renamed or restructured.
Historical Dictionary Support
Both Bouvier's and Burrill's treat ex rel. as an abbreviation only, directing readers to the full entry for ex relatione. This is instructive: in the 19th-century legal world, ex rel. was treated as a caption convention rather than a substantive legal concept in its own right, and the real analytical work lived under the procedural doctrine of the relator.
Bouvier's illustrative example — equity suits to restrain public nuisances brought on the information of affected private parties — captures the core historical use well. Burrill's adds the clearest structural explanation: the people or state prosecutes, but the aggrieved party is the relator behind the action. Neither source anticipates the False Claims Act qui tam context, which emerged from federal statutory development and represents the term's most significant modern expansion.
What neither historical dictionary fully addresses is the theoretical tension ex rel. always carried: the government holds the nominal cause of action, but the relator holds the practical interest. Modern courts and commentators have had to work out questions of relator standing, settlement rights, and control over litigation that 19th-century sources left unresolved precisely because the procedural device had not yet been stress-tested in its current statutory form.
Jurisdictional Note
Federal and state practice diverge substantially. The federal False Claims Act qui tam mechanism is purely statutory and governed by federal procedural rules. State ex rel. practice for mandamus and quo warranto varies by state constitution and statute — in some states the attorney general has discretion whether to bring the action; in others the relator may compel it. Researchers should not assume federal ex rel. procedure maps onto state practice or vice versa.
Encyclopedia Cross-Reference
family_171: Domestic Violence — Emergency / Ex Parte Orders of Protection (The Law Mind Family Law Encyclopedia) — relevant for distinguishing ex rel. from ex parte in the context of emergency judicial relief.