Definition
A Latin phrase meaning "of infirmity." In medieval English legal procedure, de infirmitate was the principal essoin — a formal excuse for non-appearance in court — grounded on the claim that the absent party was too ill or physically incapacitated to attend. It was the standard excuse recognized in the period of Glanville (late twelfth century) for a party who could not present themselves before the court on the appointed day. The essoin de infirmitate effectively suspended proceedings and gave the absent party additional time, subject to procedural rules governing how the excuse was to be vouched and verified. The term was later superseded in common usage by the phrase de malo (specifically de malo lecti or de malo veniendi), which carried forward the same essential concept of illness-based excuse under a different label.
Common Confusion
De infirmitate and de malo are not competing doctrines — they are successive names for the same procedural device. Researchers encountering de malo in later medieval sources should understand it as the functional continuation of de infirmitate, not a distinct or broader category. The shift in terminology reflects evolving common law pleading conventions rather than any substantive change in the underlying rule. Confusing the two as separate essoins would distort any account of the chronological development of the essoin system.
Why It Matters in Research
This term appears almost exclusively in sources dealing with early English common law procedure, concentrated in the period before and immediately following Glanville's Tractatus de Legibus (c. 1187–1189). Researchers working in medieval legal history, the history of civil procedure, or the development of excused absence doctrines will encounter de infirmitate as a landmark term in tracing how the common law managed non-appearance.
Two navigational points deserve attention. First, because the term was displaced by de malo relatively early, primary sources from the thirteenth century onward will rarely use de infirmitate directly. A researcher following the doctrine forward must pivot to de malo and its subcategories. Second, Reeves' History of the English Law (the source cited in all three dictionary entries) is the key secondary reference — the citation to "1 Reeve, Eng. Law, 115" (or "Hist. 115" in Burrill) points to John Reeves's treatment of essoins, which remains the standard historical account in the secondary literature for this procedural period. Glanville's own treatise is the primary source of record.
Burrill's entry is notable for embedding a cross-reference to de ingressu (writ of entry) immediately following the de infirmitate entry, which reflects Burrill's alphabetical organization rather than any substantive connection between the two terms. Researchers should not infer a doctrinal link.
Historical Dictionary Support
All three historical dictionaries reproduce essentially identical language, tracing de infirmitate to Glanville and directing readers to de malo and essoin. This uniformity signals that the term was already archaic legal history by the time these dictionaries were compiled — Black's and Burrill's are reporting on a medieval concept, not a living doctrine. None of the dictionaries elaborate on the procedural mechanics of how the essoin was formally lodged, how infirmity was verified, or the consequences of a fraudulent excuse. For that level of detail, the dictionaries point implicitly to Reeves and to Glanville. Researchers needing procedural depth should go directly to those sources rather than relying on dictionary summaries.