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Case Law: Headnotes and Key Numbers


Legal publishers add a number of editorial enhancements to case decisions they publish. Headnotes are one of the most important editorial enhancements to cases because each highlights a specific legal issue found in the case and can lead researchers to other cases addressing that same issue. Headnotes are available in Westlaw and Lexis platforms.

In Westlaw, headnotes are drafted by human editors and summarize the language of the case. Lexis uses computer algorithims to search cases for potential headnotes, and the headnote language comes directly from the cases.

Both Westlaw and Lexis assign topics and subtopics to each headnote. West further assigns each topic and subtopic a "Key Number" that is used across all West publications; it is essentially an index, and can be used as such in Westlaw and in print (see next box). In Lexis Advance, researchers can click on links stating "Narrow by this Headnote" to identify cases on similar issues. Lexis does NOT use the Key Number system.

Key Numbers

West's publishers created a hierarchical subject index of the law found in West's Analysis of American Law. The index is divided into 450 topics. Within those topics are subtopics and each of the subtopics has been assigned a Key Number. As cases are sent to the reporter's, West editors review the cases and write head-notes for each major point of law. The headnotes are assigned one of these Key Numbers and then reprinted in the digest according to their Key Number.

To learn more review Westlaw's Topic and Key Number Quick Reference Guide. 
Thomson Reuters has also created a video explaining the editorial process.

West Digest Key Numbers