Definition
A Latin term from medieval English legal practice meaning an escape from prison or custody. Evasio appears in writs and procedural forms as the technical designation for the act of a prisoner breaking free from lawful confinement, whether from a jail, gaol, or the custody of an officer. The term is not a substantive offense in itself but a descriptive label used in formal pleading and original writ practice to identify the fact of escape.
Common Confusion
Evasio should not be confused with the modern English "evasion" as used in criminal or tax law contexts (e.g., tax evasion, evading arrest). Those are substantive offenses carrying their own elements and penalties. Evasio is a procedural term of art from old writ practice, not a criminal charge or cause of action in its own right. Researchers working across historical and modern sources risk conflating the Latin procedural label with modern statutory offense language.
Why It Matters in Research
Evasio is a term of the writ system and will appear almost exclusively in pre-modern English legal materials — principally in Register of Writs (Registrum Omnium Brevium) sources, Fleta, and related treatises on old practice. Researchers should not expect to find the term operative in American case law or post-Judicature Acts English sources; it belongs to the era of original writs and their formulaic language.
The primary trap here is anachronism. A researcher encountering evasio in a historical record or treatise and assuming it maps onto a modern charge of escape or evasion will likely misread the procedural posture of the document. In old practice, the term appears as a description within the writ or pleading, not as the name of an indictable offense.
For corpus research, evasio connects directly to materials on gaol delivery, the writ of capias, and the law of escape more broadly. The related substantive law — governing liability of jailers for permitting escapes, and the distinction between voluntary and negligent escape — is developed in treatises separately from the writ terminology. Researchers following this thread should move from the Latin procedural label outward to those substantive doctrines.
Historical Dictionary Support
All three source dictionaries are in close agreement. Black's (both editions) and Burrill define evasio identically: a Latin term from old practice meaning escape from prison or custody, with shared citation to Reg. Orig. 312. Burrill adds a second citation to Fleta, lib. 1, c. 26, § 4, which provides modest additional historical grounding — Fleta being a late thirteenth-century treatise on English law that addresses prison-keeping and escape in a structured way.
None of the dictionaries elaborate on the substantive law surrounding escape; they treat evasio purely as a vocabulary entry for writ practice. This is appropriate given the term's function, but it means the dictionaries offer limited help to a researcher who needs to understand the legal consequences that followed from an evasio — for that, the sources themselves (Fleta, Bracton, the Register) must be consulted directly.
Jurisdictional Note
Evasio is a term of English common law writ practice with no direct American counterpart. American courts adopted the common law of escape in substance but did not carry over the Latin procedural vocabulary of the old writ system. The term will not appear in American primary sources.