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Legal Research: An Overview: Caselaw Searching

Caselaw Search Techniques

As discussed in the Secondary Sources section of this research guide, secondary source citations to the leading cases on your topic can be invaluable to jump start your research.  Some sources, such as ALR articles, will identify a great depth of cases, and other sources, such as jury instructions, may only identify a handful.  Most secondary sources fall somewhere in between in their range of case citations.  

Once you have located an on point case, you can use other techniques discussed on this page, particularly headnotes and citing references, to find other relevant cases.

Headnotes typically are included at the beginning of cases, before the court's actual opinion.  Each headnote is a short summary of a single legal principle discussed in the case.  Headnotes are written by editors, not the court.  While headnotes are not part of the actual opinion, they are a valuable research tool.

Each headnote is assigned a legal topic / subtopic.  In Westlaw, these topics / subtopics are referred to as Key Numbers.  In Lexis, they are referred to as legal topics.  In Bloomberg, they are considered topics but are assigned an alpha.numeric designation.  To see the topic that each designation represents, click on the "Show Topic Path" link that follows the designations.  

The topics / subtopics correspond to those in the online digests discussed at that tab on this page.

Using the following approach, you can use one relevant case that you have found to find other relevant cases:

  • Read the case.
  • Find the headnote the discusses the point at issue.
  • Identify the relevant Key Number (Westlaw)/Topic (Lexis & Bloomberg).
  • Click on the hyperlink for that Key Number (Westlaw)/Topic (Lexis & Bloomberg).
  • Select the jurisdiction and apply any other appropriate filters.
  • Review your search results.

Once you have identified a relevant case, you can use the available citator to find cases that discuss and cite to your case.  As discussed in the Validating Your Research section, Westlaw, Lexis, and Bloomberg all offer citator services identifying cases and secondary sources that reference your case.

One of the most effective way to use the citator is to start by identifing a relevant headnote.  Headnotes are discussed in more detail at the Headnotes/Topic & Key Number Systems tab on this page.  Both Westlaw and Lexis, include a feature that allows you to see what cases cite to your case for the legal proposition identified in the headnote.  If there are cases, that cite to the specific legal principle in the headnote:

  • Westlaw will include a link in that headnote to "Cases that cite this headnote" identifying how many cases cite to your case on the issue represented by that headnote.  

  • In Lexis, headnotes include a link to "Shepardize -- Narrow by this Headnote" which also identify how many cases cite to that headnote.  

Clicking on these links will take you to a list of cases that cite to your case for that legal proposition.  In both Westlaw and Lexis, there are filters at the left of the list that can be used to narrow your search results.

Another way to use the citator to find other relevant cases is to explore the other materials (cases, secondary sources, etc.) that cite to your case.  

  • When you are in a case in Westlaw, look at the tabs above the case name for "Citing References."  Explore the Citing References to see what cases and secondary sources have cited to your case.  When looking at cases that have cited to your case, you can use the filters at the left to narrow your search results by jurisdiction, depth of treatment (i.e. how detailed is the discussion of your case), by headnote topic, and by other factors.  In addition, there is a search feature at the left that allows you to keyword search within the search results.  

  • In Lexis, you can see a similar report of citing references, with similar features to narrow your search results, by clicking on the link to "Shepardize® this document" at the right of your case.  

  • In Bloomberg, the citing reference report is available by clicking on "BCITE ANALYSIS" at the right of your case and then selecting "Citing Documents."  You can also go directly into the citing cases in Bloomberg by selecting "Case Analysis."

When your topic involves a statute or a regulation, using annotated codes is a terrific starting point to identify relevant cases.  As discussed in the Statutes and Regulations sections of this research guide, annotated statutory and regulatory codes will identify cases that discuss and cite to the statute or regulation at issue.  

Each publisher of code annotations uses its own editors and algorithms to generate case references.  Accordingly, there will be some differences in the cases identified in the statutory annotations for each code publication.  

Moreover, the features for reviewing citing cases varies a bit between Westlaw, Lexis, and Bloomberg.  For example, as discussed in more detail below, Westlaw can be used to filter cases both by jurisdiction and topic, and Lexis can be used to view cases that cite to subsections of statutes.  

Once you pull up a relevant statute or regulation, to review case annotations:

  • In Westlaw -- You will see a number of tabs towards the top of your document, that look something like,

The case references are available at the "Notes of Decisions" and "Citing References" tabs.  While not including case law, the "Context & Analysis" tab provides references to secondary sources and other materials that discuss in-depth the statute/regulation at issue.  Accordingly, this tab should not be overlooked.

The "Notes of Decisions" provides a topical index to certain cases that discuss the statute or regulation.  Cases relating to each subtopic are linked to from the index.  It is a good starting point for finding cases relevant to a statute/regulation but does not include all citing references, as it tends to focus only on those with in-depth analysis relating to the identified subtopics. 

Select "Citing References" To see the full list of cases, secondary sources, and other materials that cite to the statute/regulation.  To just look at cases, select "Cases" from that list.  You will get the list of cases, and at the left, there will be options for filtering the results by jurisdiction, by publication status, and by whether or not the case was identified in the Notes of Decisions.

Citing References can be filtered by jurisdiction but Notes of Decision cannot.  However, within Citing References, there also are filters to select cases that are referenced in the Notes of Decision and to view the specific "Notes of Decision Topics" covered.  These filters can be used to hone in on cases within a particular jurisdiction covering a specific topic.  For example, if you were working with the above statute and wanted to see what topics within the Notes of Decisions were represented by cases from the 9th Circuit, you would go to the Citing References, and select "Cases."  From there you would go to the filter for "Jurisdiction," expand the menu for "Courts of Appeals," and select "Ninth Circuit Ct. App."  Then you would scroll down to the filter for "Referenced in Notes of Decisions," select "Yes", and click on the link to "Select NOD Topics."  That opens up a list of topics addressed by the cases from the 9th Circuit that were identified in the Notes of Decisions.  The filters and topics look like:

  • In Lexis -- The annotations are at the end of the document, after the statutory/regulatory language and history notes.  The annotations include "Case Notes," which is a topical index of certain cases that discuss the statute/regulation.  Following the case notes are "Research References & Practice Aids," which identifies related statutes, regulations and secondary sources that discuss the statute.  

Additionally, there is a link at the right of the document to "Shepardize® this document." Selecting that option will create a report of citing cases and other citing sources. Filters are available at the left of the reports to narrow your search results.  It is recommended that you look both to the "Case Notes" and to the Shepard's report to see all the case citations for a given statute/regulation.

Lexis also allows you to view citations to subsections of statutes and regulations.  This is very useful when you are working with a large statute/regulation and only portions of it are at issue.  To get to the case citations by subsection, first get into the Shepard's report for your statute/regulation.  From there, select "Citing Decisions," and you should see an option towards the top of the report for "Subsection reports by specific court citation."  This should look like:

Selecting subsections reports opens up a menu identifying the different ways courts have cited to your statute/regulation.  This includes references to specific subsections, when those subsections have been specifically cited.  Select the subsection that is most relevant for your research to open up a report of citing reference for that subsection. 

To see subsection references in secondary sources, follow the same process as detailed above but view "Other Citing Sources" (rather than "Citing Decisions" ) in the Shepard's report.

  • In Bloomberg -- To the right of the code/regulation section there is an icon to select "Smart Code™."  Selecting that opens up a link to "Launch Smart Code™." The Smart Code report will identify cases that cite to the statute/regulation and gives you options to filter the results.

Keyword searching is similar to the kind of searching you would do in Google -- just smarter.  When doing keyword searches for cases, it is not uncommon to get a large number of search results that are not particularly on point, especially if your search terms are quite broad or non-unique.  However, keyword searching is an important research skill and a good supplement to other research methods.

Some tips for effective keyword searching include:

  • Narrow your search to the relevant jurisdiction.

  • Generate a list of keywords relevant to your research question, including common synonyms for each of your keywords.

  • Use the keywords, including the synonyms, to craft your search.  Consider using the search builder techniques discussed in the Search Techniques section of this research guide.  That section identifies strategies for crafting effective searches and provides several sample searches to illustrate each technique.

  • Explore the advanced search features available in the search engine you are using to see if any of those features will assist in making your search more effective.

  • Some search engines give you overview type search results, almost as an introduction to the complete set of results.  It is useful to review the overview results, but be mindful also to look at the full listing of results.  See the Search Techniques section of this research guide for more information regarding working with search results, including evaluating overview search results.

  • Once you have run your search, use the filters available in the search engine to refine your search, particularly if your search gave you more results than are practical for you to review.  Commonly used filters for cases include published / unpublished, jurisdiction, and court.

  • When reviewing search results, be mindful of your options for sorting results.  You should have the option to sort results by relevance or by date (most to least recent and visa versa).  You may also have the option to sort cases by most cited.  If you have more results than are practical for you to review, you may want to consider sorting by relevance and reviewing the first fifty or so results and then resorting by date (newest first) and also by most cited (if available) and reviewing the first 50 or so hits for each sort.  This will allow you to hone in on the most relevant, most current, and most prominent results.  

  • If your first search was not spot on (and it rarely is), refine your search.  The search results from your prior search(es) should provide some good clues on how to make your searching more effective.  For example, maybe you need to make better use of boolean techniques, or perhaps you need to adjust your keywords.

For more information on crafting effective searches and working with search results, see the Search Techniques section of this research guide.

At its most basic, a digest organizes the universe of case law by topic.  The topics used in digests correspond to the topics used in headnotes, discussed in more detail in the Headnotes/Topic & Key Number Systems tab on this page.  In fact, digests typically are compilations of case headnotes.  

Within each broad digest topic, there usually are numerous subtopics, each with their own numerous subtopics.  For example, in the Westlaw digest, the topic "Constitutional Law" includes twenty eight broad subtopics, and each of these subtopics has anywhere from three to well over a hundred subtopics.  An on point digest topic / subtopic is a valuable research tool.  Digests were originally published in print.  Today, while print digests still exist, most researchers use them online.  Westlaw, Lexis, and Bloomberg all have online digests.

The most common way to identify a relevant digest topic / subtopic, is from the headnotes of cases.  Headnotes appear at the beginning of cases.  Each headnote is a short summary of a single legal principle discussed in the case, and each headnote is assigned a legal topic / subtopic.  A relevant headnote can be used to access the corresponding legal topic / subtopic in the online digest, which will identify other cases discussing that same legal principle.

Digests can also be searched and browsed to determine relevant topics / subtopics.  The following will assist you with working with the online digests in Westlaw, Lexis, and Bloomberg.

  • Westlaw
    • The online digest in Westlaw is referred to as "Key Numbers."  
    • The digest can be accessed by clicking on "Key Numbers" from the Westlaw home page (in the column at the far left on the "All Content" menu).
    • That takes you to a list of 414 broad topics, listed alphabetically.
    • You can browse the topics.  Once you find a relevant topic, click on it to see the subtopics for that topic, and keep expanding the subtopics to hone in on what is most relevant for your research.
    • As an alternative to browsing the topics, you can use the "Search for Key Numbers relevant to your issue" feature that appears above the list of topics, and/or you can use the "Title Search" feature that appears below the list of topics.  Using these search features will allow you to see the topics / subtopics specific to your search terms.  However, proceed with caution when using these search features.  The search engine for these features does not seem as robust or as reliable as with general Westlaw searches.
    • It is NOT recommended that you use the search box at the very top of the page (in the top blue bar above the page title "West Key Number System)."  That seems to take you directly into the cases, bypassing the topic / subtopic organization of the Key Numbers.  This search defeats the purpose of using the Key Number system.
    • Once you have determined the topic / subtopic(s) you would like to review, click on the subtopic to see a list of relevant cases.  You can use the filters on the left to narrow your results by jurisdiction and date.
  • Lexis
    • The online digest in Lexis is available from the "Browse" menu at the upper left of the home screen.  
    • From the Browse menu select "Topics" to get a list of more than forty broad topic areas.
    • Each topic has numerous subtopics, and the subtopics also tend to have subtopics.  After selecting the topic relevant for your research, explore the available subtopics to find the one most relevant.  
    • Once you have drilled down through the subtopics and selected one, you are given certain options, including "Get documents" and "Add topic as a search filter."
    • Selecting "Get documents" takes you to a list of relevant materials, including cases.  You can use the filters on the left to narrow you search results by jurisdiction, publication status, and other factors.
  • Bloomberg
    • The online digest in Bloomberg is called "BNA Classification Outlines" and is available from the "Litigation & Dockets" menu from the main "Browse" menu.
    • Bloomberg's Classification Outline is narrower in scope than Westlaw's Key Number system and Lexis' Topic.  There are fourteen broad topics in Bloomberg's Classification Outline, most of which relate to business law.  However, for the topics covered, the Classification Outline is a rich source of information.
    • From the Classification Outline, select the topic relevant to your research to be taken to a the complete topical listing for that broad topic.  
    • Find the subtopic relevant for your research, and click on the link next to that subtopic (which will be a letter.number designation) to be taken to a list of materials relating to that subtopic.
    • For cases, select "Court Opinions" from the "Content Type" menu at the left.  That will take you to a list of cases, and you can use the filters at the left to narrow the search by jurisdiction and other factors.