Finding cases to support your arguments

When an appellate court decides a case they will often write an opinion, called case law, that says what they decided and how they interpreted and applied the law to the case. You can use these opinions to support how a judge should apply the law in your situation.

Case law

Case law is the previous decision by judges forming principles for interpreting the law

These opinions help courts decide what to do in new cases. This is called legal precedent. Whether or if a court must follow case law depends on many factors, like if the case has the same type of facts as yours, which court decided the case, and when it was decided. 

If you find a case you want to use to support your legal arguments, you will want to figure out if the case is still valid (called good law) and if it is a case that the court must follow. Even if a court is not required to follow it, it may find it persuasive. Other legal research guides will have more information about how to do this. A law librarian may also be able to help explain. Finding cases that best support your legal arguments is one of the harder parts of legal research.

You look up case law by its citation, which has its name and where to find it

Often legal guides and other legal texts will include references to case law. These references are called citations. A citation tells you the name of the case, where to find it in a book, and the year it was decided. 

Example case citation:

  • Hutcherson v. Alexander, 264 Cal. App. 2d 126, 70 Cal. Rptr. 366 (1968).
  • United States v. Dionisio, 410 U.S. 1 (1973).

Different citation formats can be used, but they all provide the same information. Once you have this information, you can look up the case online or in a reporter

How to find case law

Most of the legal issues in state courts relate to state law. So, you will be researching California state court cases. In some cases, like a civil rights case, you may need to research federal case law. If you do use federal case law, you will need to know whether and how the state courts will apply these laws. Ask a law librarian for help. You may need to talk to a lawyer. 



You can find California case law online or at a law library

Law libraries have cases in print or available online through a legal database. Most libraries offer access to legal databases you can use at the library. Some offer remote access to these databases so you can use them anywhere. These databses can be very helpful as they will also include links to other relevnt cases and other legal resources. Find out your options on their website or by going to the library.

You can also find California Court of Appeals and Supreme Court cases online for free. This can be helpful if you already know what case you are looking for.


Federal court opinions can be found online from different types of federal courts.

The federal court system includes the Supreme Court of the United States, U.S. Courts of Appeals, U.S. District Courts, the U.S. Court of Federal Claims, U.S. Court of International Trade, U.S. Court of Appeals for the Armed Forces, and U.S. Bankruptcy Courts.

U.S. Supreme Court opinions.

The U.S. Courts of Appeals consist of 11 circuit courts in addition to the District of Columbia Circuit and the Federal Circuit. California is in the Ninth Circuit along with Alaska, Arizona, Hawaii, Idaho, Montana, Nevada, Oregon, and Washington. Click for information about and opinions issued by the Ninth Circuit Court of Appeals. For information about the other circuits, you can go to your local public law library or use the Ask a Law Librarian service.


California is divided into four U.S. District Court jurisdictions: the Northern District, Eastern District, Central District, and Southern District. Click for opinions and other information from the Central District,  Eastern DistrictNorthern District, and Southern District.  You can also access opinions in federal courts using the Villanova University School of Law federal case locator.


The U.S. Bankruptcy Courts in California are also divided into the Northern District, Eastern District, Central District, and Southern District. Each district has information online including opinions for the bankruptcy courts. Click on the district for which you want the information.