If motive is not required to prove a crime why is cui bono important?

Full Question:

Several legal references online state that motive is not necessary to prove that a crime has been committed. How do I reconcile this with several legal references that state that "Cui bono" is useful in finding the guilty?
04/08/2017   |   Category: Criminal   |   State: Texas   |   #35362

Answer:

Cui bono means what did the person have to gain by committing the crime. It is similar to motive but there are crimes where there was nothing to gain and no motive.