The science as you said is clear, the embryo is a living human being.
Where we disagree is that you think courts have the constitutional power to define when life begins. They don't, they never have and they never will.
That kind of power was never given to unelected judges. "The people" knew better.
No one is "defin[ing] when life begins. "
All they're doing is defining what is legal and illegal wrt abortion.
A verdict of "justifiable homicide" hardly means that the victim wasn't alive; it just means that no penalty attaches to killing him (because he was attacking you, or threatened to kill your neighbor, ...).
I don't like Roe v Wade, criminal statutes should be up to the states unless they're in conflict with the Federal Constitution or Federal statutes.
"Unelected" or not, the Justices who ruled on RvW were duly appointed. I don't think poor decisions constitute "bad behavior" as grounds for removal. I have been in states where judges are elected, and I didn't like it at all; I think the Fed. Const. got that provision right.