To trigger the felony murder rule, a felony must be independent from the death caused.
This is often assessed by asking if the felony would merge into a murder charge because it is a lesser-included charge. If so, it is not independent.
As an example, an assault that results in a death is not independent. A defendant cannot be convicted of both assault and murder for the same act. In contrast, rape never merges into murder, so the independent felony rule would never apply in such cases.