Definition
ATS is a Latin-derived legal abbreviation standing for "at the suit of." It appears in case captions and legal documents to identify the party at whose initiative a suit is brought — that is, the plaintiff or moving party — from the perspective of the named defendant. Functionally equivalent to the abbreviation "ads." (ad sectam), ATS signals that the named party before it is the respondent or defendant, not the initiating party.
In historical case reporting and court records, a case styled "Smith ATS Jones" reads as "Smith, at the suit of Jones" — meaning Jones is the plaintiff and Smith is the defendant. The caption is written from the defendant's vantage point, which was a common convention in older English and early American practice.
Common Language
Modern common usage (Wiktionary): Plural of "at."
Historical common usage (Webster's 1913): No relevant entry; "at" functions as a preposition of location or time.
The legal abbreviation ATS has no meaningful connection to the common English word "at" or its plural. Researchers encountering "ATS" in historical legal records should not parse it as an ordinary English word — it is a compressed Latin formula, at suit of, functioning as a structural label within a case caption.
Common Confusion
ATS is frequently confused with ads. (ad sectam) because the two abbreviations are functionally identical. Both signal that the named party is the defendant and that the suit was brought by another. Anderson's Dictionary treats them as direct equivalents. Neither abbreviation indicates anything about the merits of the case or the nature of the claim. Researchers should also be alert to a separate modern usage: in contemporary federal litigation scholarship and practice, "ATS" commonly refers to the Alien Tort Statute (28 U.S.C. § 1350), an entirely distinct term. Context — historical versus modern, caption versus text — is the reliable disambiguator.
Why It Matters in Research
The primary research trap with ATS is the collision between its historical meaning (at the suit of, a caption abbreviation) and its modern shorthand meaning (Alien Tort Statute). A researcher working in nineteenth-century case reporters who encounters "ATS" is reading a defendant-perspective caption convention. A researcher working in modern human rights litigation or federal jurisdiction scholarship who encounters "ATS" is almost certainly reading a reference to the Alien Tort Statute. Treating these as the same term will produce significant confusion.
Within the Law Mind historical corpus, ATS in caption position should be read as a structural marker, not as substantive content. It tells you who is the defendant but nothing about the cause of action, the court, or the procedural posture. When indexing or searching historical records, researchers should treat ATS and ads. as interchangeable and search both.
The abbreviation also reflects an older convention of writing case captions from the defendant's perspective — a practice that largely disappeared from American reporting by the twentieth century as plaintiff-first captioning became standard. Researchers comparing pre- and post-convention records may find the same dispute captioned in opposite order depending on the era and the source.
Historical Dictionary Support
Anderson's Dictionary of Law (1889) gives a spare but accurate entry: "At suit of; equivalent to ads ad sectam." This captures everything the abbreviation does. No significant divergence exists across historical sources on this point — ATS is a narrow, stable abbreviation with a single historical legal meaning. What historical dictionaries collectively miss is the modern secondary usage as a shorthand for the Alien Tort Statute, which postdates them entirely and has become the dominant meaning of "ATS" in contemporary legal discourse.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Case Captions and Party Designation; Alien Tort Statute (for the modern ATS usage).