Definition
In legal usage, "intervals" appears almost exclusively as a component of the compound term LUCID INTERVALS — periods of mental clarity experienced by a person otherwise suffering from insanity, dementia, or other mental incapacity. Standing alone, the word carries no independent legal definition of significance. Its legal weight derives entirely from the doctrine governing what a person may lawfully do during such intervals: executing a will, entering a contract, or otherwise performing legal acts that require mental competence.
Common Confusion
Do not conflate "intervals" in the mental capacity sense with "intervals" as used in time-computation provisions of statutes and rules (e.g., filing deadlines computed at specified intervals). Context will distinguish these uses, but the distinction matters when running corpus searches.
Why It Matters in Research
Researchers encountering "intervals" in older legal sources — particularly in cases involving testamentary capacity, contract validity, or guardianship — should treat the term as a flag directing attention to the lucid intervals doctrine. The standalone use of "intervals" in a legal text almost always presupposes the full phrase; abbreviation was common in older legal writing and in index entries. Bouvier's, for example, uses "intervals" as a compressed cross-reference pointing the reader toward LUCID INTERVALS and its associated doctrines.
The practical research trap: searching corpus materials for "intervals" without the modifier "lucid" will surface a large volume of irrelevant hits — scheduling provisions, time computation statutes, periodic payment clauses — before reaching the mental capacity doctrine that likely prompted the search. Narrow early.
Jurisdictional variation in the lucid intervals doctrine itself is substantial. The threshold of clarity required to establish a lucid interval sufficient for testamentary capacity differs from that required for contractual capacity, and historical courts were not uniform on what evidence sufficed to prove one had occurred. Medical jurisprudence treatises from the nineteenth century are often the most useful bridge between legal holdings and clinical language in older corpus materials.
Historical Dictionary Support
Bouvier's does not define "intervals" as a freestanding legal term. The entry functions purely as an index node, directing the reader to LUCID INTERVALS and to a cluster of related medical-legal topics: INSANITY, MANIA, DEMENTIA, IMBECILITY, IDIOCY, DELIRIUM FEBRILE, DELIRIUM TREMENS, HYPNOTISM, KLEPTOMANIA, SOMNAMBULISM, APOPLEXY, and ILLUSION. This architecture reflects nineteenth-century legal practice, in which capacity questions were highly granular — the cause of mental impairment was considered legally relevant, not merely the fact of impairment. A researcher in historical sources must therefore follow Bouvier's implicit instruction: the doctrine of intervals cannot be understood without also understanding the specific condition producing the incapacity.
Bouvier's cross-reference to Jones's Index to Law Periodicals and the St. Louis Law Library Catalogue signals that interval-related capacity questions generated substantial periodical literature, much of it now accessible only through specialized historical collections.
Encyclopedia Cross-Reference
See: LUCID INTERVALS