When doing research for American law information, after finding the statutes and cases you are looking for you need to make sure that this primary law is still "good law".
What does it mean?
Since you have started doing research, the law you are relying on may have been overruled, reversed, or invalidated by other cases or statutes. You can also verify if there are other cases or legal resources that cite your case or statute, giving you the possibility to expand your research even further.
This is the process of validating legal sources and it involves the use of the so called citators, lists of opinions and law journal articles that cite back to a specified case and tell you anything that has happened since publication, and if your case or statute remains good law.
Citators include references to subsequent legal materials that have cited a particular case.
One of the most famous and used citations was developed by Frank Shepard in the early 1870s, and the process of validating the law has become commonly known as "Shepardizing."
Here you can find a recap of the signals you can find in the Shepard's Citation Service:
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