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LRAW Research Spring 2025

Purpose of Secondary Sources

The main goal of legal research is to efficiently find primary, mandatory authority on your legal issue.  

Secondary sources are often the best place to begin your research, because secondary sources can provide:

  1. citations to primary authorities, quickly taking you to the top statutes or cases.
  2. context and commentary on primary authorities, helping you understand which cases are most relevant, and how to extract rules from those cases and apply them in your legal analysis.

Compare benefits of starting with secondary sources to starting with keyword searches:

1. Citations to Primary Authorities

A keyword search may help us find cases with one click, but whether those are the most relevant cases or not depends on how we constructed our search and whether the search algorithm was built to understand such a search. Running more searches using more keywords doesn't provide a reliable doublecheck on our search results when we don't know what we don't know

The source that leads us fastest and most reliably to what human experts agree are the leading authorities on an issue is most often a secondary source.

Example 1: An attorney asked a clerk for case law on an issue. The clerk did keyword searches of case law, and found tons of cases addressing that topic. However, for some reason the lawyer said those cases were not relevant. It turned out, there was a statute on point that the lawyer forgot to mention. The cases the clerk found used the same terms the lawyer mentioned, but those cases didn't interpret the statute the lawyer had in mind.
If you start with a secondary source, it will mention any relevant statutes because secondary sources contain citations to primary authorities. You know from our units on statutes that if you first look up a statute, then you can use Annotations / Notes of Decisions as well as Citing Decisions / Citing References to find cases interpreting the statute.

2. Context and Commentary on Primary Authorities

A keyword search may help us find cases with one click, but it may be time-consuming to read these cases and extract applicable rules

Efficiency increases if we can read the rules from significant cases first, and read in plain language how courts interpret the relevant statutes and cases: this is what secondary sources provide. Then when we read the full text of the cases, we are reading with increased understanding, and can more quickly and accurately determine which cases are helpful and how to use them.

Example 2: An attorney asked a clerk to find a case precedent for the rule that if a majority of shareholders in a company vote a certain way, then what they voted on must take place. The clerk found many, many, endless cases mentioning all these terms, but only as dicta. The attorney mentioned that there might not be a case on point. The only way there would be a case on point would be if parties had sued and appealed over that issue, rather than settle. It wouldn't make financial sense for anyone to sue and appeal based on a position so obviously incorrect that one is sure to lose. How long should the clerk continue searching through search results for a case that probably does not exist, but might?
If you start with a secondary source, it will explain legal concepts from first principles. If there is a case on point, that case will be referenced in a footnote. If there is no reference to a primary source in any secondary source that states the rule, then a secondary source may well be the best available source to cite for the obvious statement.

Secondary sources can also help you narrow, expand, or redirect your research as needed.

Example 3: A clerk starts time-sensitive research by doing a keyword search for case law. The clerk finds far too many cases to sift through in the time available, so the clerk tries totally different keywords and now sees only one case that appears relevant to the issue. The clerk once again changes keyword search strategy, runs a new search, and now there are no case law results, and the clerk doesn't know why.
If you start with a secondary source, you can handle all of these scenarios. See below.


  • Too many case law results, that all appear relevant? Look first at the cases that are cited by secondary sources. These are probably the most important cases on the topic.
  • Too few, or no relevant case law results? Skim secondary sources, looking for:
  1. other terminology that may be used in court opinions, to help you include more relevant terms in your search,
  2. tables of contents to expand your search to include a broader topic area than the narrow focus you might have started with, or
  3. explanations that may help you understand why there actually aren't many cases on your topic.

Limitations of Secondary Sources

Secondary sources are a beginning, not an end point, because secondary sources have limitations.


When the law changes, a secondary source can become outdated. This includes online versions. Always check the publication date of the secondary source you are consulting. Update the primary sources it cites, to ensure they are still good law. 

A secondary source may not include everything necessary for your analysis. You must not rely solely on the commentary found in a secondary source, but carefully read the primary sources it cites to determine if they are on point for your precise legal issue.

Also, remember that secondary sources are always persuasive and never binding on courts. Secondary sources are most often used for background, context, and help locating the strongest primary authorities. Secondary sources should not be cited when trying to persuade a court, if binding authority (such as a relevant case decided by a higher court) is available.

Types of Secondary Sources

In this Secondary Sources Unit, we will look at how each of these types of secondary sources can be helpful starting points to shed light on a research question:

  • Legal dictionaries
  • Legal encyclopedias
  • Legal treatises
  • Law review & journal articles
  • American Law Reports (ALRs)
  • Restatements
Research Question: A client presents you with the following facts. 

A young boy trespassed into a national park to get to a hill well-known for sledding. On his first pass down the hill, he was severely injured by a tree support wire that was strung from a tree to the ground. He later died of his injuries.

Your client, a relative of the boy, wants to bring a wrongful death action in federal court against the National Park Service.

The National Park Service claims that the attractive nuisance doctrine cannot apply to allow recovery because it was the sledding hill, not the wire, that attracted the child onto the property.

You need to learn more about the attractive nuisance doctrine.