Key Number System Law and Legal Definition

A key number system is a legal research indexing system introduced by West Publishing Company to catalogue American case law with head notes. In this system, a number designates a point of law and helps a researcher to find all reported cases addressing a particular issue by referring to its number. Key number system is an index to find opinions relevant to the legal problem that one is working on. This system also helps to identify the issues one needs to consider in the first place while working on a legal problem. It is the most comprehensive and widely used indexing system for case law materials.