Is she guilty? (details inside.)

A book that I am reading brought up an interesting question… here is the scenario:

A woman wanting to poison her husband puts arsenic in his apple, but he throws it away. A homeless person fishes it out of the trash, eats it, and ultimately dies. Has the woman murdered him?
What if a man goes to the house of a depressed woman carrying a rope and a box. He ties one end of the rope to the rafter, the other end into a noose and places the box below. Suppose he convinces her to put her head in the noose and kick the box out from under herself. Has he murdered her?

I found both of these very difficult to answer for myself… curious to hear from my jellies.