What about Judith Jarvis Thomson's famous defense of abortion? She argued that even if we fully accept that a fetus is a person, it doesn't necessarily follow that this person has a right to use a woman's body as a life support system.
"Suppose you wake up one morning and find that a famous violinist's circulatory system has been plugged into yours, so that your kidneys can be used to extract poisons from her blood as well as from your own. She needs to remain plugged into you for nine months. If you unplug her, she will die because there is no other person who has the right blood type. Here is a clear situation in which the violinist's right to life comes into conflict with your right to control what happens to your own body."
It's not at all self-evident, in Thomson's example, that declining to be someone else's life support system is identical to murder.
Barry