what are those riddles called where you ask yes or no questions to find out how...

[Brookewilson]

...someone died? my teacher used to do those in class for us.. they have a certain name. what are they called?

 

[Ookami no Eichi]

If you are referring to riddles such as "A man is found lying dead in an open field with nothing but an unopened package beside him. How did he die?", then what you're looking for is called a "Lateral Thinking Puzzle."