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Case Law - What It Is & Where to Find It: Case Law

What is Case Law & Why is it Important?

  • Case Law is a primary source of law.
  • Primary sources of law include: case law, statutes, constitutions, rules and regulations.
  • Case Law is created by the Judicial Branch. Statutes and Constitutions are created by the Legislative Branch. Rules and Regulations are created by the Executive Branch.
  • Case law, also known as common law, is the body of law created by judicial decisions.

The United States' common law judicial system adheres to the doctrine of stare decisis, which requires judges to follow the legal precedent established in previous cases. Therefore, in order to determine what the law is regarding a particular point of law, it is crucial to be able to locate previous controlling and relevant case decisions. 

Key Numbers

Key Numbers are unique to products published by West. They represent a specific subtopic within an area of law. They are uniform throughout all West Publications, and are therefore very useful in finding primary and secondary resources on the point of law you are researching.

Click the Key Numbers tab for more information.

Locating a Case by Citation

A case citation is a reference to the location of a case in a reporter (a multi-volume set of books).

A case citation consists of the case name (plaintiff v. defendant), volume number, name of the reporter (abbreviated), page number and year the case was decided:

Muscarello v. United States, 524 U.S. 125 (1998).

The case above  (Muscarello v. United States) can be found in Volume 524 of United States Reports on Page 125. This case was decided in 1998.

A parallel citation references the location of the same case in more than one reporter:

 Muscarello v. United States, 524 U.S. 125, 118 S.Ct. 1911,  141 L. Ed. 2d 111 (1998).

  • Volume 524, United States Reports, Page 125
  • Volume 118, Supreme Court Reporter, Page 1911
  • Volume 141, Lawyers Edition 2nd Edition, Page 111


Once you've found a case on point, citators (which can be found on Westlaw's, Lexis' and  Bloomberg's legal research databases) can help you answer the following questions:

  • Is the case still good law?
  • What is the case's judicial history?
  • Can I find additional cases that support my position?
  • Can I find other primary & secondary materials that cite to my case? 

Click the Citators tab for more information.


The full text of case opinions can be found in multi-volume sets of books called reporters. Lexis and West publish unofficial reporters. These reporters contain editorial enhancements, however, the case opinions are the same as the ones published in the official reporters. In some jurisdictions, there is no official reporter (e.g., Federal Supplement & Federal Reporter).

The Reporter page details: which cases are reported in each reporter; which reporters are official; and the reporters' abbreviations.

Reporters are organized:

  • Jurisdictionally (Federal or State)
  • Hierarchically (trial court, intermediate appellate court, highest appellate court)
  • Geographically (State or Region)
  • Chronologically

Legal Research Databases

For decades, the two major legal research databases have been Lexis (now Lexis Advance) & Westlaw . Recently Bloomberg, a long-time business research database, launched its own legal research database. Other lower cost legal research databases include Fast Case, Casemaker and Lois Law. Google Scholar is a free legal research resource, however it does not currently include a citator. Click here for more information on the major databases.