Definition
In a like case; in a similar case. A Latin phrase used in common law pleading and statutory interpretation to signal that a legal rule or remedy applicable in one set of circumstances should extend by analogy to a materially similar set of circumstances. The phrase is most closely associated with the Statute of Westminster II (1285), which authorized chancery clerks to issue new writs in cases similar to those already covered by existing writs — effectively permitting the common law to develop analogically rather than remaining frozen in its original forms.
The phrase functions as a doctrinal shorthand: where a prior rule, writ, or precedent governs a particular situation, in casu consimili signals that the same legal logic governs the analogous case now before the court.
Common Confusion
IN CASU CONSIMILI and IN CONSIMILI CASU should be treated as the same term. The transposition of casu and consimili reflects ordinary variation in medieval and early modern legal Latin and carries no substantive distinction. Researchers indexing or searching historical sources should query both forms.
Why It Matters in Research
This phrase is almost never used in isolation in primary sources. When researchers encounter it, they are almost certainly reading a passage about the extension of writs under the Statute of Westminster II or a commentary on that statute's effect on common law development. The phrase is a marker pointing toward a much larger doctrinal story about how equity and the common law writ system evolved in tandem.
The critical research trap: Burrill's entry is a bare cross-reference to IN CONSIMILI CASU, which is the operative form under which substantive doctrine is discussed. Researchers who stop at this entry will miss everything of substance. Follow the cross-reference.
Historical sources treat IN CASU CONSIMILI and IN CONSIMILI CASU as effectively interchangeable, with the latter being the standard form in legal discourse. Word-order variation in medieval Latin phrases is common and does not signal a difference in meaning. If you encounter one form in a source and the other in an index or digest, treat them as the same concept.
The phrase matters most in research on: (1) the history of the English writ system and the role of the Chancery in creating new writs; (2) the origins of equitable jurisdiction as a supplement to common law remedies; (3) early statutory interpretation and the analogical extension of statutes; and (4) the development of the forms of action before their abolition in the nineteenth century. Any of these research threads will require understanding this concept.
Historical Dictionary Support
Burrill's Law Dictionary provides only a one-line entry directing the reader to IN CONSIMILI CASU. This is consistent with the phrase's secondary status — it is a variant form, not the primary doctrinal term. The entry confirms equivalence but offers no independent analysis.
The absence of substantive treatment in Burrill reflects a broader pattern in historical legal dictionaries: Latin variant forms of established phrases are catalogued but not expounded upon, on the assumption that the researcher will follow the cross-reference to the canonical form. For a phrase like this one, the canonical form carries all the weight.
No meaningful divergence exists across historical sources on the meaning of this phrase. The variation is purely one of word order (in casu consimili vs. in consimili casu), not of substance.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Statute of Westminster II; Forms of Action; Development of Equity Jurisdiction.