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Lehigh University Libraries - Library Guides

JOUR 122: Media Law and Ethics

Case Law Explained

Case law -- also known as common law or precedent -- is law developed through the judicial system, or court decisions, rather than through the legislative or executive branches. 

With legal research, case refers to the written decision/opinion of a judge or group of judges. These written decisions serve as precedent-- that is, they will be important to subsequent decisions. 

Courts whose decisions are published are almost always appellate courts.   Many cases' decisions will only be available at the courthouse where the legal proceedings were held.

This LibGuide will help you locate electronic case law resources. 

Image source: Wikimedia Commons, CC-BY-SA-3.0

Sources of Case Law

To find case law, you'll need to know the court from which the opinion originated.  U.S. Supreme Court opinions are very easy to locate.  Lower federal and state courts can be a bit more difficult.

Information on which court heard your case can often be can be gleaned from the citation of the case or from a quick Google search. 

After you know the court your case was argued in, use the sub-tabs to the left to locate case law resources from: the U.S. Supreme Court, State Courts, Pennsylvania Courts.


In order to locate case law, it's crucial to understand the structure of the U.S. court system.

Basically, both federal and state courts have the same hierarchical structure.

All cases begin in the trial courts.  If the trial court decision is appealed, the case will move to an intermediate appellate court.  If appealed again, the case moves to the final appellate court, which is often, but not always, known as the Supreme Court.

In the U.S. court system, only intermediate appellate court and Supreme Court cases are published.  Most trial court decisions are not published.

Use the tabs to the left to locate case law.

Image source:  Wikimedia Commons.  CC-BY-SA-3.0

Background Information