for the lawyers-when is a fetus a human? has that been decided? are there not legal protections for people who kill murderers in defense of helpless victims?
Careful getting the lawyers involved. There was a drunk driving case in Missouri a couple of years ago. The state legislature had passed a law saying life began at conception, and some lawyer tried to use that as a defense saying that if life began at conception then his client was 21 years and 5 months old when he was arrested for DWI, and therefore shouldn't be charged under the more strict underage drinking laws. I don't think he won.
I'm not an attorney, but I'll try to answer your question.
Among pro-choice people, only the idiots try to deny that the fetus is alive and that it is human. These are scientific facts and can't be effectively disputed.
In Roe and its followup decisions, the Supremes have decided that while the fetus is a living human, it is not a person under the law and has none of the rights of a person, not even the right to not be intentionally killed.
We thus are in the interesting position of having as a society decided that legally some living humans are persons and others are not.
We aren't even consistent in this, as fetuses can still be considered murder victims in some states and result in increased penalties for the killer of the pregnant woman. Fetuses can also inherit and sue for damages, after they're born, of course.
In practice, the only difference between a fetus that is a person and one that is not is the attitude of the pregnant woman. She wants the baby, it's a person. She doesn't want the baby, it's a blob of tissue that can be discarded at will with no legal consequences.
Oddly enough, despite the general liberal admiration for Europe, they ignore that, AFAIK, every European country has more restrictions on abortion than the USA.