Definition
Latin: "moved or excited by anger or passion." A pleading term of historical English common law, used in the context of the plea of son assault demesne to characterize the defendant's state of mind at the time of an alleged assault. The phrase indicated that the defendant acted under the provocation of anger or passion, forming part of the defensive narrative that the plaintiff had initiated the confrontation and the defendant's response was heated rather than calculated.
Common Confusion
The abbreviation "IRA" in modern legal and tax contexts refers almost exclusively to an Individual Retirement Account — a creature of federal tax law with no connection to this Latin phrase. Researchers encountering "IRA" in modern materials are virtually never looking at this term. The Latin phrase ira motus appears only in historical common law pleading sources and is entirely unrelated to retirement account law. Any search involving "IRA" in a modern corpus will return tax and financial materials, not pleading doctrine.
Why It Matters in Research
This term has essentially no practical presence in modern legal research. Its significance is purely historical and confined to a narrow slice of common law pleading doctrine — specifically the formal structure of the plea of son assault demesne in English practice.
Researchers should be aware of two traps. First, keyword searching for "IRA" in any Law Mind corpus will surface retirement account materials overwhelmingly; isolating ira motus requires full Latin phrase searching. Second, even within historical sources, the term appears rarely — all three dictionary sources point to the same single citation (Tidd's Practice), suggesting the phrase had limited circulation even in its own era and was more a technical ornament of pleading than a substantive legal standard.
The connection between ira motus and the broader doctrine of provocation is worth noting for researchers tracing the historical roots of heat-of-passion defenses. The phrase captures an early common law acknowledgment that emotional state was legally relevant to characterizing violent conduct — a thread that runs forward into criminal law doctrines of voluntary manslaughter and provocation, though ira motus itself belongs to civil pleading, not criminal law.
Researchers working in historical tort materials, early American pleading practice, or the history of the assault and battery cause of action may encounter this term in treatises and practice guides predating the nineteenth-century shift away from formal common law pleading forms.
Historical Dictionary Support
Black's Law Dictionary (both editions) and Burrill's Law Dictionary are in complete agreement: all three define ira motus identically as "moved or excited by anger or passion" and identify its use as a term "sometimes formerly used" in the plea of son assault demesne. All three cite the same authority: Tidd's Practice (1 Tidd, Pr. 645).
The uniformity across sources, combined with the word "formerly" appearing in all three entries, signals that even at the time these dictionaries were compiled, ira motus was already archaic — a term preserved in the dictionaries as a record of superseded pleading practice rather than as a living term of art. No dictionary offers a substantive doctrinal discussion; the entries are definitional placeholders pointing researchers back to a single treatise source.
What the historical dictionaries do not address is the broader doctrinal significance of anger or passion as a legal concept, nor do they connect ira motus to the developing law of provocation in either tort or criminal contexts. That connection must be pursued through other sources.
Jurisdictional Note
Ira motus is a term of English common law pleading with no recognized jurisdiction-specific American variant. Its appearance in American sources reflects the reception of English common law forms; it does not represent a living doctrine in any U.S. jurisdiction.