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Legal Research at Princeton: U.S. Law: Case Law

Finding U.S. Case Law

The most effective way to conduct case law research in at Princeton is to use Westlaw Campus* (available from the Library's Articles & Databases page). However, the best way to use Westlaw Campus, is TO HAVE A RELEVANT CASE CITATION, BEFORE USING WESTLAW CAMPUS.

So, go to Westlaw Campus "armed" with the citation of a relevant case!  Where do you find a relevant case law citation?  Secondary sources! For example, law journal articles, treatises, even a Google search.  By starting out in Westlaw Campus with a citation, it will be much easier to find more cases on your topic than it is to start Westlaw Campus without a citation.  See the "Getting Started -- Secondary Resources" tab for more information about secondary legal sources.  See below to learn how to find cases on a topic in Westlaw Campus when you start out with relevant citation.

Once you have your citation, enter the Westlaw Campus database and pull up your case by entering its citation in the "Find a Document by citation" search box on the left hand side of the "Law" tab.  See below to learn how to understand a case law citation.

*Note: If Westlaw Campus asks for a password, please click the refresh button on your browser. This should allow access to the database without putting in a password.


Understanding a Case Citation

In order to go to Westlaw Campus "armed" with a relevant citation, it's important to understand how to read a case law citation.  While you can pull up a case by its name ("Brown v. Board of Education"), it is easier to use a citation because a name search will almost always result in multiple cases with the same name.  By using a citation, you will retrieve your exact case on your first try!

Cases are published chronologically in case law reporters.  There are different reporters for different courts and jurisdictions.  See below ("Detailed Information on Case Law") for more detailed information about case law reporters.

The structure of a case citation is “volume# / reporter abbreviation / first page of case”:


Reporter Abbreviation

First Page of Case





Sample Citations:
U.S. Supreme Court (official):      120 U.S. 354
U.S. Supreme Court (West):       189 S. Ct. 698
Federal Reporter:                       1 F.3d 67
Federal Supplement:                  33 F.Supp.2d 87
Atlantic Reporter:                       608 A.2d 1341  

A full case citation includes the case name, all reporters where the case appears, court information (except for the U.S. Supreme Court) and year:

Brown v. Board. of Ed., 347 U.S. 483, 74 S.Ct. 686, 98 L.Ed. 873 (1954).
National Abortion Federation v. Gonzales, 437 F.3d 278 (2d Cir. 2006).
Hollenbaugh v. Carnegie Free Library, 436 F.Supp.1328 (W.D. Pa. 1977).
Hummel v. Reiss, 608 A.2d 1341, 129 N.J. 118 (N.J. 1992).

Finding Cases on a Topic After You Have a Case Citation

Once you have a relevant case citation, and have pulled the case up on  Westlaw Campus* there are 3 main ways to find more cases on a similar topic: (1) look at the cases cited by the court in your case; (2) find the cases that cite your case; (3) use the case "headnotes" to find more cases on your topic.

(1) Look at the cases cite by your case

This is quite simple, as you read your case on Westlaw Campus, every case that the court cites will by hyperlinked.  By clicking the link, a window will pop up (leaving your case on the main screen) to reveal the case being cited, at the page within the case where the court is citing it.  You can begin to collect cases on your topic by starting with the cases cited by the court in your case.

(2) Find the cases that cite your case

To pull up all the cases that have cited your case, access your case, and then click the "Citing References" link on the left hand side of the screen.  This will retrieve all the cases, and other documents, that have cited your case.  First on the list will be citing references called "negative history."  Negative history citing references are the cases that do not follow the reasoning of your case exactly.  The are NOT overruling or overturning your case, but are not following its logic completely.  If your case has any of these negative citing references, it will receive a yellow flag at the top of the screen (more on these flags below in the section on discovering whether your case has been overruled).  After the negative history will be the positive history.  The positive history are all the cases that cite your case, and follow the reasoning of your case.  This are listed from the cases that spend a lot of time analyzing your case ("Four-Star Cases") to the cases that just mention your case ("One-Star Cases").

After all the cases are listed, other types of documents (law review articles, court documents, etc.) will be listed.  Because this list of document can be very long, you can use the "Limit Key Cite" display button toward the bottom of the screen to cut the list of citing references to documents in which you are more likely to be interested.

(3) Use the case "headnotes" to find more cases on your topic

In Westlaw Campus the text of each case is preceded by little paragraphs called "headnotes."  Each headnote is a summary of a legal point made in that case.  In turn, each headnote is assigned a code that corresponds to the topic of that headnote.  By clicking on the hyperlinked codes preceding each headnote, you can find headnotes from other cases that have headnotes with the same topic code.  Once you click the link a new search screen will appear.  You can add search terms, or choose your jurisdiction and then run the search to find headnotes from other cases with the same topic code as the headnote in your case.

In sum, if your case has a headnote that is just you topic, follow the headnote to other cases on that same topic!

Has Your Case Been Overruled?


Cases are frequently reversed or overturned.  Therefore, if you want to verify that a case’s ruling is still good law you must use a citator.  There are two different case law citators: Shepard’s (on Lexis) and KeyCite (on Westlaw and Westlaw Campus).  The process of updating case law is often called “shepardizing” or “keyciting.” 

Shepard’s and KeyCite are powerful research tools that tell the researcher much more than whether a case is still good law.  Shepard’s and KeyCite are “windows into the future” of a case.  In other words, when you shepardize or keycite a case, you will learn happened to that case and to the legal rule from that case, after it was decided. 

When learning how to shepardize and keycite, it’s helpful to think of the following scenario:  you’ve found a case and before using it you want to find out information about that case that is not available just from reading it. The three major types of information Shepard’s and KeyCite provides about “your case” are:

  • History: other court opinions from the same litigation handed down before “your case” was handed down.
  • “Subsequent History”: court opinions from the same litigation that were handed down after “your case” was handed down or court opinions from other litigations that affect the validity of the ruling in “your case.”  From this information you will learn:
    • If the case was reversed on appeal (and your case is “bad law”)
    • If the case was affirmed on appeal
    • If the case was modified on appeal
    • If the case was overturned by a ruling in another litigation (and your case is “bad law”)
  • “Citing References”: all cases, law review articles and other resources that have cited “your case.”  From this information you can find other cases on the same subject (since cases that cite each other are usually about the same subject) both those that agree and disagree with the court in “your case.” 

Citing references are designated according to how they treat the case you are shepardizing/keyciting (“your case”) as positive (meaning citing reference agrees with “your case”) or negative (the citing reference disagrees with “your case”).  KeyCite breaks down the negative treatment into more subcategories, such as “Called into Doubt” or “Declined to Extend” or “Distinguished.”

How to Use Shepard’s / KeyCite

Shepard’s (online) and KeyCite are quite simple to use.  First, pull up the case you are interested in shepardizing/keyciting. You can do this by entering the citation or by doing a full-text or digest search.

Once you have the case on the screen:

  • On Westlaw: keycite the case by clicking a link (full history, direct/graphical history, or citing references) in the white KeyCite box to the left of the case.
  • On Lexis: click the Shepard’s link.  This will bring up both the history (prior and subsequent) and all citing references.  You can limit the list of citing references to negative or positive treatment of “your case.”

Full-Text Searching to Find Relevant Cases

What about full-text searching?

Of course, searching case law full text is a very powerful tool for finding cases on your topic.  For most projects at Princeton, however, it is recommended that you only turn to full-text searching after you've used all the strategies discussed above and on the secondary source page.

There are 2 ways to search case-law full text on Westlaw Campus.  NOTE: Lexis Academic is very similar to Westlaw Campus for full-text searching.

The first is Basic Searching

Basic searching is similar to Google searching.  Just enter in your terms and click search!  The drawback is that Westlaw Campus will always retrieve 100 cases, even if only 3 are actually relevant, or even if there are 1000 relevant cases.  So, while easy to use, it is always likely to be either over-inclusive or under-inclusive.  Basic searching is a great way to get started, to find that first relevant case, and then use the tools described above in the text box titled, "Finding Cases on a Topic After You Have a Case Citation," to find more relevant cases.

The second is Advanced Searching

Advanced searching is the classic and most powerful way to search cases full-text in Westlaw Campus (note that searching case law in Lexis Academic works on very similar principles as Westlaw Campus).  For the novice, it can be a bit tricky.  The search technology used is very different from the key word searching you may be used to from other databases and Google.  As a result, it takes some practice to become an effective full-text searcher on Westlaw (or Lexis).

IMPORTANT NOTE:  The advanced search screen on Westlaw Campus looks deceptively like the key word search screens that are common in many databases.  It's appearance is such that you may think to enter in one search term, choose "and" or "or" from the drop down menu, and then enter another search term.  In most databases this would be a decent way to do a key word search.  However, because Westlaw Campus is doing a word proximity search, it will find all cases that contain those words, not the cases that are about those words as key terms.  Therefore a simple "and" or "or" search is usually not helpful.  To get around this, enter in your entire search phrase in the first searching field according to the descriptions and examples below.

Rather than searching key words, Westlaw Campus will do a "word-proximity" search.  This means that you must tell the system exactly which words you want your case to contain, and in what proximity to each other.  See the (oversimplified) sample searches below:

RED or BLUE or GREEN or "SEA FOAM":  This will retrieve cases that have any of these words in them.  Note that quotation marks around phrases are required.

RED! BLUE GREEN "SEA FOAM":  Westlaw Campus interprets a space as an "or".  Note the "!" after the term RED.  This will tell the system to retrieve RED, REDDISH, REDDER, etc.

RED & BLUE & GREEN & "SEA FOAM":  This will retrieve cases that have all of these search terms.

(RED or BLUE) & (GREEN or "SEA FOAM"):  This will retrieve cases that have RED and GREEN, RED and "SEA FOAM", BLUE and GREEN, or BLUE and "SEA FOAM".

RED /s BLUE:  This will retrieve cases that have the word RED in the same sentence as the word BLUE.

GREEN /p "SEA FOAM":  This will retrieve cases that have the word GREEN in the same paragraph as the phrase "SEA FOAM".

GR*Y /10 "NAVY BLUE": This will retrieve cases that have the word GRAY (or GREY -- because of the *) within 10 words of the phrase "NAVY BLUE".

JU("JOHN PAUL STEVENS"): This will retrieve all cases in which Justice John Paul Stevens was the judge.

TI(BROWN and "BOARD OF EDUCATION"):  This will retrieve all cases with parties named Brown and Board of Education.

AU(KIM /3 SCHEPPELE): The AU (author) function is best used when searching for law journal articles on Westlaw Campus.  This search will retrieve articles written by an author whose contains the word Kim within 3 words of the word Scheppele.  It is often better to use the /3 connector rather than quotation marks ("KIM SCHEPPELE") in case the the author is listed with a middle initial or a middle name.  "KIM /3 SCHEPPELE" will return articles where the author is Kim L. Scheppele.  A search for "KIM SCHEPPELE" will not.

DA(BEF 1/1/1998): Retrieves cases dated before 1/1/1998.

DA(AFT 1/1/1998): Retrieves cases dated after 1/1/1998.

Note that these connectors can be combined to conduct very specific and powerful searches:  

(GREEN /p "SEA FOAM") and (GR*Y /10 "NAVY BLUE") and DA(BEF 1/1/2005) and DA(AFT 1/1/2000) and JU(JENNIFER /3 SMITH).

These examples are only some of the options.  For more detailed information CLICK HERE for a lesson in Advanced Searching (also called Terms & Connectors searching).

Alternative Databases to Find Cases


This research guide is geared to the use of Westlaw Campus, which is available available to the Princeton University community through the Articles & Databases link on the Library’s web page.  However there are other databases that contain U.S. case law:

Lexis Academic: Discussed only briefly in this guide, Lexis Academic has very similar coverage of legal materials as Westlaw Campus. It is available available to the Princeton University community through the Articles & Databases link on the Library’s web page.

Westlaw Commercial & Lexis Commercial: Westlaw Campus and Lexis Academic will serve most research needs of the Princeton community.  The Princeton University Library maintains a very limited number of passwords to Lexis and Westlaw’s commercial versions.  If you find that Westlaw Campus and Lexis Academic are not meeting your research needs, please contact the Law Librarian, who will help you with the research and/or provide access to the commercial Westlaw and Lexis (David Hollander,, (609) 258-5316).

Detailed Background Information on Case Law



Why would a legal researcher care what a judge decided in some legal dispute between two private parties?  Central to the U.S. legal system is the idea of binding authority and precedent

When a higher court publishes a decision on a point of law, that decision is binding on all lower courts in the same jurisdiction.  The lower courts in that jurisdiction must follow earlier judicial decisions when the same points of law arise again in litigation.  A court opinion that has this power has binding authority or precedent. This concept is formally called stare decisis (Latin – “to stand by things decided”).

Because this power extends only to lower courts in same jurisdiction as the higher court, often legal research will require a basic understanding of jurisdiction and court system structures.  The federal court system and most state court systems maintain a three-tiered structure.  The table below illustrates this typical structure in the federal system, New Jersey and New York.


Court System Structure*


Typical Court
System Structure

State Courts (vary by state)
(New Jersey)
(New York)


Federal Courts

High Court

State Supreme Court
(Supreme Court of NJ)
(NY Court of Appeals)

United States Supreme Court


Appellate Court

State Appellate Court(s)
(Appellate Division)
(Appellate Division)

United States Circuit Courts of Appeals


Trial court

State Trial Courts
(Superior Court of NJ)
(Supreme Court of NY)

United States District Courts


*Note that in NY, the trial court (the lowest court) is called the “Supreme Court.”  Also many jurisdictions maintain several types of trial level courts in addition to the main trial court.  These can include family courts, traffic courts, criminal courts, municipal courts, county courts and many others.

The U.S. Supreme Court’s opinions are binding on all courts in the U.S. In the federal system, the country is divided up into 13 circuits, each having a Circuit Court of Appeals, whose opinions are binding on all trial courts (District Courts) in that Circuit.  New Jersey is part of the Third Circuit.  The Third Circuit Court of Appeals sits in Philadelphia.  New York is part of the Second Circuit and its Court of Appeals sits in New York City.  A map of all the circuits is posted at

Each state has its own system for carving up the state and assigning jurisdictions.  If your research requires knowledge of these jurisdictional divisions, many states post this information on the state court system’s web site.  Another helpful resources is the National Center for State Court’s web site:


 Case Law Reporters

Court opinions are published more or less chronologically in case law reporters.  Cases from different jurisdictions are published in different reporters.  Some courts, but not nearly all, still publish official reporters. The major publisher of unofficial case law reporters is West.  When possible, it’s helpful to use the West reporters when researching case law in print.  West has designed an indexing system that makes finding cases by subject rather easy.  This will be discussed in the section below on digests. 

The table below outlines the federal case law reporters.  Only the Supreme Court maintains an official reporter.





U.S. Supreme Court

United States Reports (official)
Supreme Court Reporter (West)
Lawyers’ Edition  (Lexis)

S. Ct.
L. Ed.

Federal Circuit Courts of Appeal

Federal Reporter (West)
Federal Reporter 2nd Series
Federal Reporter 3rd Series

F. 3d

Federal District Courts

Federal Supplement (West)
Federal Supplement 2nd Series

F. Supp.
F. Supp.2d


For state case law, the West Regional Reporters publish opinions from the high courts and some intermediate appellate court of the 50 states.  The table below lists all the states and the regional reporter where the case law from that state is printed.






Atlantic Reporter
Atlantic Reporter 2nd Series



Northeastern Reporter
Northeastern Reporter 2nd Series



Northwestern Reporter
Northwestern Reporter 2nd Series



Pacific Reporter
Pacific Reporter 2nd Series
Pacific Reporter 3rd Series



Southeastern Reporter
Southeastern Reporter 2nd Series



Southwestern Reporter
Southwestern Reporter 2nd Series



Southern Reporter
Southern Reporter 2nd Series



New York Supplement
New York Supplement 2nd Series



California Reporter
California Reporter 2nd Series
California Reporter 3rd Series

Cal. Rptr.
Cal. Rptr.2d
Cal. Rptr.3d


All of the regional reporters are full-text searchable on Westlaw Campus, Lexis Academic, Westlaw Commercial, and Lexis Commercial.  However, only the West products allow access to West’s digest system for finding cases by subject.  For more information, see the sections below on digests and Westlaw.



West is the major private print publisher of case law reporters.  In addition to the text of the court opinions, West includes several features that help the researcher quickly understand the case and find cases on a similar topic.  The following research features appear in West case law reporters, after the court name, case parties, docket number, and date, but before the actual court opinion begins:

West Summary: a small paragraph briefly summarizing the entire case.  This paragraph is written by editors at West Publishing, not the court, and therefore may not be cited as law.

Opinions Included: a listing of the of the court opinions, any concurring dissenting opinions, the authors or each opinion, and if applicable, who joined in each opinion.

West Headnotes and Key Numbers: one or more small paragraphs with a heading (consisting of a number, topical heading, and an icon that looks like a key with another number).  These paragraphs summarize the each legal point and is assigned a “Topic” and a “Key Number” that represents a subtopic.  The number at the left of the heading is the number of the headnote and will correspond to a number in the text of the court opinion where the court makes the legal point summarized in the headnote.  In the example headnote below, the headnote is headnote 1.  A number 1 will appear in the text of the court opinion where the legal point summarized in the headnote is made.  The Topic is Negligence and the Key Number is 210.  The headnotes are a good way to quickly learn what legal rulings the court made before reading the text of the case (which can sometimes be difficult to read).  The topic and key number are used to find other cases that address that same topic.  This is addressed in the section below on digests.

[1] Negligence 210
272k210 Most Cited Cases
(Formerly 272k2)
In every instance before negligence can be predicated of a given act, back of the act must be sought and found a duty to the individual complaining, the observance of which would have averted or avoided the injury.

Court Syllabus:  a summary of the court’s opinion, written by the court, but not part of the actual decision.  Most opinions do not have a syllabus.  Usually it is only U.S. Supreme Court decisions.  The court’s syllabus is longer than the West summary.  This syllabus may not be cited as law.    

Attorneys: following the syllabus (or, in the absence of a syllabus, following the headnotes) is a listing of the attorneys involved in the court case.

The Opinion: only after the listing of the attorneys does the court’s opinion begin.

Contact the Law Librarian

Law and Legal Studies Librarian
Firestone Library - SSRC