A system devised by West Group involving the classification of legal subjects that are organized within their publications according to specific topics and subtopics. Each topic and subtopic is given a key number which consists of one or more digits preceded by the symbol of a key assigned to each individual classification.
A particular point of law can be traced through different law books by following the cases listed under a Key Number in each series. West Group, formerly the West Publishing Company, developed the Key Number System of Classification during the decade spanning 1897–1906. The system is a valuable research tool because once the topic and Key Number have been located, a researcher has ready access to all American cases that have litigated that issue provided those cases have been reported. More than 425 Key Numbers in the system are arranged by subject matter under seven main headings—persons, property, contracts, torts, crimes, remedies, and government—and 32 subdivisions of the system.
Key Numbers are also a vital component of Westlaw™, an online resource for conducting Computer-Assisted Legal Research. The Key Numbers employed on Westlaw are identical to those used in the print counterparts to the on-line system.
Kunz, Christina L., et al. 2000. The Process of Legal Research. 5th ed. Gaithersburg, Md.: Aspen Law & Business.