Case Law Research

Headnotes & Key Numbers

In Part 1- Anatomy of a Case, we learned that a case has many components in addition to the actual text of the opinion. Headnotes and Key Numbers are editorial enhancements that you can use to find additional cases addressing similar issues.

  • Headnote: A brief summary of a legal rule or significant facts in a case.
  • Key Number: It is an indexing system devised for American case law, developed by West (now Thomson Reuters). The key number is a permanent number given to a specific point of a case law.
    • The key number system is available on Westlaw, but not on Lexis Advance and Bloomberg Law. 
  • As stated above, headnotes and key numbers are NOT part of actual text of a judicial opinion. So please do NOT cite them in your writing assignment.

Westlaw

Westlaw headnote and key number. Once you find a relevant headnote, click the key number to find more cases. If you don't see key numbers, click Change View.

  • (If you do not see key numbers, click "Change View")
  • Headnote 2 provides a summary of legal rule (elements of defamation under Maryland law)
  • Libel and Slander is the topic. 237 is the number assigned to the topic.
  • The topic Libel and Slander has many sub-topics.
    • 237k1 Nature and elements of defamation is the relevant sub-topic assigned to Headnote 2.
  • Click on 237k1 to find additional cases discussing the elements of defamation.

Lexis

Lexis does not have a key number system. However, it provides headnotes for case. You can find additional cases on the topic by clicking on a headnote and selecting "Get Documents" 

Lexis Advance headnotes. to find additional cases discussing the same topic, click on a headnote and select "get documents"