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Essential Legal Research Skills for Law Students: Case Law

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Case Law

From the Federal Judiciary website:

"The Judicial Branch has two court systems: federal and state. While each hears certain types of cases, neither is completely independent of the other. The two systems often interact and share the goal of fairly handling legal issues.

The U.S. Constitution created a governmental structure known as federalism that calls for the sharing of powers between the national and state governments. The Constitution gives certain powers to the federal government and reserves the rest for the states.

The federal court system deals with legal issues expressly or implicitly granted to it by the U.S. Constitution. The state court systems deal with their respective state constitutions and the legal issues that the U.S. Constitution did not give to the federal government or explicitly deny to the states.

For example, because the Constitution gives Congress sole authority to make uniform laws concerning bankruptcies, a state court would lack jurisdiction. Likewise, since the Constitution does not give the federal government authority in most family law matters, a federal court would lack jurisdiction in a divorce case."

As in the federal court system, New York's court system is three tier, consisting of trial courts, intermediate appellate courts, and the highest court. In New York the trial court is called the Supreme Court, the intermediate court is called Appellate Division, and New York's highest court is the Court of Appeals.

There are 62 trial courts - one for each county. There are four Appellate Division departments - Appellate Division 1st Department located in New York County, Appellate Division 2d Department located in Brooklyn, Appellate Division 3d Department located in Albany, and Appellate Division 4th Department located in Rochester. There is one Court of Appeals in New York, located in Albany. 

Reported decisions from the trial courts are published in an official reporter called the Miscellaneous Reports (Misc.), currently in its third series. 

Reported decisions from the intermediate courts, New York Appellate Divisions, are published in an official reporter called the Appellate Division Reports (A.D.), currently in its third series. 

Reported decisions from the highest court of New York, the New York Court of Appeals, are published in an official reporter called the New York Reports (N.Y.), currently in its third series. New York Court of Appeals reported decisions are also published in a regional reporter, the North Eastern Reporter (N.E.), currently in its third series and published by Thomson Reuters. 

Reported decisions from all three New York court levels are published in an unofficial reporter called the New York Supplement (N.Y.S.), currently in its third series and published by Thomson Reuters.

To locate applicable case law, try:

  • Starting with a secondary source
    • Secondary sources include cross-references to primary sources, such as case law
    • Consult footnotes, tables of authorities, endnotes, references, and in-text citations
  • ‚ÄčKeyword search in legal databases
    • Westlaw, Lexis, Google Scholar, and Fastcase are all examples of legal databases where you can search for case law. Some are free, some are low cost, and some charge per hour or transaction
  • Digest research
    • West topics and key numbers, a proprietary system created by West, provides subject access to case law. It is used to expand your research when you use the "one good case method" of legal research
  • Citators
    • KeyCite on Westlaw and Shepard's on Lexis are examples of citators. Citators are used to validate (determine whether a particular case is still good law) and expand legal research 

The One Good Case Method of legal research starts with finding one good case - a case that is on point.

  • By using that case's applicable headnotes you can expand your research. Understanding the headnote system and knowing how to use it can be a powerful tool for legal research. West headnotes are consistent across all U.S. jurisdictions. Thus, you may identify a point of law summarized in headnote from a case in one jurisdiction and use that headnote to find similar cases in a different jurisdiction. Headnotes allow for cross-jurisdictional research
  • Use KeyCite, Shepard's, or BCite to find cases that have cited your one good case.
  • West headnotes consist of four parts:
    • Number - indicates the number of a headnote assigned to a case. These numbers are assigned consecutively, so a case can have one headnote or many headnotes.
    • Topic - indicates the broader topical category to which a particular point of law belongs. Click here (log into Westlaw) to see the full list of 450 West topics
    • Key Number - indicates the subtopics of the broader topic
    • Summary of the point of law - a summary written by the West editors
  • West editors create one headnote for each point of law discussed in a case. This allows you to go right to the part of a case discussing that point of law
  • A case can have anywhere from few to a number of headnotes, depending its length and intricacy. For example, Bell Atl. Corp. v. Twombly, 550 U.S. 544 (2007) has 18 headnotes, where People v. Green, 529 N.Y.S.2d 852 (App. Div. 1988) has only one headnote.
  • West headnotes describe the abstract principles of law in a case and facilitate searching for cases addressing the same principles of law
  • N.B. West headnotes are not part of the opinion of the court and should never be cited!



citator is a tool that helps you determine what happened to your case, statute, or regulation after it was released: appeals of cases, amendment or repeal of statutes and regulations. The major online citators are Shepard's (available on Lexis) andKeyCite (available on Westlaw).




  • To verify authority - Is your case or statute still good law?
  • To expand research - Find cases and other sources that have cited your case or statute. 
  • To find direct history 
    • Cases include prior and subsequent history
    • Statutes include reversal, amendment, or pending legislation

The development of online citators has improved and decreased the amount of time researchers need to verify the law. Before online citators, researchers used Shepard's Citators in Print, published by Lexis. If you are interested, click here to learn more about Shepardizing in print