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Finding Case Law

Sources and strategies for finding case law about a topic.


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Scott Vanderlin
Instruction and Outreach Librarian
D'Angelo Law Library
Subjects: Law

What is a Citator?

Legal citators are valuable tools that list primary and secondary sources that have cited a particular document, e.g., a judicial opinion. Citators help you determine the status of a law, e.g., whether a case is still “good law” (that it has not been overruled by another decision), or whether a statute has been found unconstitutional. Before you submit any work product, such as a memorandum or a brief, your last step should always be to update your research by using a citator to check that the sources you cited are still good law.

Citators are also helpful for telling you what happened procedurally in a particular case, e.g., that the case was appealed. Citators can also help you find additional research resources that cite the source you’ve located. See the “One Good Case” Method page of this guide.

Citators categorize the citing references in various ways, including by treatment (whether the citing opinion was positive, negative, etc.), jurisdiction, and depth of treatment. These filters allow you to locate citing references that are directly relevant to the issue you are researching.

Each of the major legal research platforms has its own citator, and each one uses its own unique methodology. You will find that they rarely produce the exact same results. See the subsequent boxes for more information on each citator.

Westlaw - KeyCite

Within a case, KeyCite provides three main features for checking a case's history:

Westlaw screenshot: using KeyCite tabs


  1. Negative Treatment: lists only the citing cases from the Citing References tab that negatively referenced this case
  2. History: explains the evolution of this case by providing links to previous and subsequent opinions
  3. Citing References: lists all the sources (including secondary sources and so on) that cite to this case

For a detailed explanation on using KeyCite, also see this guide:

Lexis Advance - Shepard's

View this short video to learn how to use Shepard's in your research.