The logical organization of legal materials is essential to the maintenance of a legal system based on precedent. For more than 100 years, the legal community has relied on the Topic and Key Number System's organization of case law to locate that precedent.

But what is the Key Number System... and why do I need to know about it? West's Key Number System is, simply put, the most comprehensive and widely used indexing system for case law issues. Understanding the Key Number System is an indispensable part of learning how to do effective legal research.

How the Topic and Key Number System Works

The Topic and Key Number System is a big outline or index that works like this:

  1. The American system of law is broken down into Major Topics -- there are more than 400 topics, such as Civil Rights, Pretrial Procedure, and Treaties.
  2. Each of those topics is divided, in greater and greater detail, into individual units that represent a specific legal concept -- like steps in an outline. There can be up to eight steps in the hierarchy to reach the narrowest concept.
  3. Each of the narrowest concepts (and there are approximately 100,000 of them!) has a unique number that allows you to find it on the outline. This number is called a specific Key Number.

Why the Key Number System is Important to Legal Research

The Key Number System makes legal research easier, more accurate, and more relevant. The Key Number System is both an index you use to find opinions relevant to whatever legal problem you are working on and an outline of issues important in the law. This means that it will not only help you find the cases you want, but it will also help you identify the issues you need to consider in the first place!

How Do I Find the Cases I Need?

Let's back up for a moment, starting with case law and working our way back to the Key Numbers. A court issues an opinion in a case. A copy of the case is obtained by West, where highly trained attorney editors read the case and pick out the points of law addressed in the case. Written as a short, concise paragraph, these are called headnotes. You've seen the headnotes before the opinion of a West reported case, both in the print reporters and online.

The headnotes are then passed along to attorney editors who are experts in figuring out where points of law belong in the huge Key Number System "outline." These "Classifiers" find the correct location on the outline, and assign at least one Key Number to the headnote. Here is the great part: all headnotes in any jurisdiction dealing with a particular point of law will have the same Key Number!

Then the West Digests take over. Digests are arranged alphabetically by Topic and then numerically by Key Number. There are regional, federal, state, chronological and topical digests. All cases dealing with a legal concept in the jurisdiction, time period, or topical area covered by a Digest are grouped together. Talk about a great research tool!! On Westlaw, all Key Numbers are hyperlinked to cases addressing the same issue in any jurisdiction.

All you have to do is know which Key Number describes the problem or point of law on which you would like to find cases. The rest has all been done for you!