Viability is not a tricky issue. Is is something that can be determined. It can be quantified. Either a fetus has reached a stage of development where it can sustain life on its own or it hasn't. In order to sustain life, certain developmental stages must be completed. If those stages have not been completed, it cannot sustain life, and therefore, is non-viable.
But see, this is where there's a lack of consistency to me. If a woman gave birth prematurely, and the baby wasn't fully developed, and the doctor just decided, "Actually, I don't think I'll put the baby in an incubator, I'll just leave it like it is", and the baby died, then that would be considered murdering that baby.
They are different because the removal of life support is simply allowing a person to follow the natural course of the disease process. The artificial component is the life support, not the death from the disease. If you stab someone, you have attempted to remove the life from them by your own choice and your own hand. You have not allowed the disease to take its natural course. One is allowing a natural death to occur, the other is taking alife, or murder.
First of all, that was specifically why I said if someone was in a coma that they could recover from. It would be considered a form of murder for a doctor not to keep that person on life-support until they got better. Also, if the argument is things taking their natural course, then abortion stops the natural course of life.
And a person in a coma has reached the point of viability, have been alive, and have sustained life. Therefore, there is a life to loose when death occurs. A product of conception, and embryo, or a first trimester feuts has not achieved life according to legal and medical standards.
Again, I just think this becomes an issue of consistency. If the judge is the current state of life, then why would it also be negligent not to attempt to resuscitate someone. If someone flatlined in a hospital, and the doctors just decided not to get a crash cart because the person was already dead, they would be held legally responsible for their decision.