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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

Searching Databases

The searching method for case law topics differs between the major case law databases of Westlaw, Lexis+, and Bloomberg Law. It is helpful to search more than one database, since the results will vary slightly. Searching multiple databases ensures that you are gathering the best case law for your topic.

Before searching in any database, you'll need to know:

  • your topic and any relevant keywords
  • which jurisdiction applies to your legal problem
  • which types of primary law apply to your topic, including federal and state statutes or regulations (see the Find Case Law from Statutes or Regulations page for more ideas)

Below, we'll talk about some techniques: constructing a search string and filtering.

Natural Language v. Terms and Connectors

Natural language searching is similar to how one searches on search engines like Google: you enter a string of keywords and rely on the search engine's algorithm to predict the relationship between terms. While you may use natural language searching in any of the legal databases, searching by terms and connectors yields more specific results based on your terms' relationship with each other - such as if you'd like the terms to appear in the same sentence or paragraph.

These operators differ slightly in each database, so please see "Boolean Searching in BLaw, Lexis, and Westlaw"  for more information about how to use terms and connectors.

Filter by Jurisdiction

To filter results by a particular jurisdiction, you may either (a) select the court(s) of interest by choosing them in the "Search:" dropdown box, or, (b) by running a search and then filtering the results. 

(a) To add filters before searching, follow these steps:

1. Click the "All Jurisdictions" dropdown box, located on the main search bar.

Lexis+ home page with the "All Jurisdictions" drop down menu in the search bar circled in orange.

2. Choose the jurisdiction(s) you would like to limit your results to.

Lexis+ jurisdiction selection screenshot

3. Once you've selected the jurisdiction(s) you are interested in, if you want to only search for case law, click on the "All Content" dropdown box and select "Cases."

(b) to apply filters after running a search, follow these steps:

1. Run your search.

2. Choose your court(s) using the left sidebar. If you need more than one jurisdiction.

Lexis+ select court post filter.

Searching By Topic on Westlaw -- West Key Number System

Westlaw includes a particularly useful tool for finding case law about a certain topic, called the West Key Number System. The West Key Number System was developed in the 19th Century by John B. West, and it is essentially an index to American Law: it uses both topics and a number system to form a classification system for legal topics. The key numbers are categorized topically in a hierarchical structure: with legal principles first categorized by broad categories followed by a narrower topic, and a Key Number is assigned to the most narrow topic. The image below is an example of this topic hierarchy:  

The West Key Number System for Abandoned and Lost Property, which shows that Key Numbers 21 - 28 are under the topic "In General."

When Thomson Reuters receives a court opinion to add to Westlaw, the attorney editors at Westlaw first review the case. They then identify what they consider to be the important legal issues, which are then summarized and categorized by Key Number. 

The document below goes over how to use the Key Number System to find cases. It is an incredibly powerful tool that has allowed researchers to find cases by subject for over 100 years. 

Searching by Topic on Lexis+ -- Headnotes

Lexis+ also has a headnote system that allows researchers to find cases by topic. The "Topics" tab (see the screenshot below) takes you to the index of main topics. Click on one of the main topics to see the subtopics. You can also search for your topic by using the "Search Topics" box. Note: you can either do a natural language search or a terms and connectors search in the "Search Topics" box.

Lexis+ Topics page captured May 2024  

If you click on a main topic, you will be taken to a page with subtopics, where you can browse to find the subtopic you want. The screenshot below is an example of this.

Lexis+ Business and Corporate Law subtopic list and hierarchy

Once you find the subtopic you are interested in, click on the subtopic link to retrieve all documents for the topic. You can then use filters to narrow your results. The below screenshot shows the results if you click on the subtopic "Management Duties and Liabilities"

Lexis+ results page when you select the subtopic "Management Duties and Liabilities." The results page is only showing cases.

Searching by Topic on Bloomberg Law -- Points of Law

Points of Law on Bloomberg Law is different from the Westlaw and Lexis+ headnotes in a couple of key ways. The headnotes in both Westlaw and Lexis+ rely on an existing classification system of topics (i.e., an index). When attorney editors at both Westlaw and Lexis+ review a case, they identify important legal points in the case, summarize them as a headnote, and assign the headnote to a topic in the index. These headnotes are located at the top of the case. 

Conversely, Points of Law uses machine learning to identify legal principles, standards, and elements in court opinions. The tool then identifies and matches the legal statements by language similarity and frequency of that legal statement (at least 5 times). The Points of Law are highlighted in the text of the court opinion itself, and you can access a list of all the Points of Law found in the opinion. The below video tutorial goes over how to use Points of Law.