There are a variety of ways to find cases. In order to find all the relevant cases on your topic, it is a good idea to try all or most of the different case finding methods. Finding cases is a circular process so you will find many of the same cases through different methods.
As Mr. West developed his National Reporter System, thousands of cases from all jurisdictions were available for the first time. He realized that he needed to develop a method to allow users to find cases on a specific legal topic.
One of the topics is Aliens, Immigration and Citizenship.
The point of this huge and elaborate classification system is to allow a researcher to find cases on a specific topic.
Finding a Relevant Key Number
You would like to find a relevant Key Number to use to find cases about knowledge asylum and force abortion/sterilization.
Aliens, Immigration, and Citizenship is one is one of the 414+ topics in the West Key Number System. You can click through the outline to look at increasingly specific key numbers. The most specific one on the is 541 - Forced abortion or coerced sterilization.
Once you find a relevant Key Number, you can click on it to find cases on the same narrow topic in your desired jurisdiction.
Once you find ONE GOOD CASE, you can use it to find additional cases on your specific legal issue.
You have found one good Ninth Circuit case about asylum and force abortion and you want to use it to find more cases.