Quote from Cutten:
Surely the way to decide when a foetus is a living individual is to define which qualities are necessary and sufficient for something to be classed a living organism, then see to what extent the foetus has them at various stages of its development. This appears to be largely an issue for biologists and the medical profession. I certainly fail to see how politics, morality, religion, or even people's feelings have anything to do with it. A woman's right to choose does not extend to the right to choose to kill another individual. There may be rare exceptions, such as a rape victim who has been denied access to an abortion until late in the pregnancy.
A fertilised egg in a woman's body has very little in common with a living human being, so I don't see how it can be classed as an individual life. A foetus 1 minute before birth has a huge amount in common with an infant 1 minute after birth, so I don't see how it can be classed as anything other than an individual life.
Somewhere in between there will be a grey area where the foetus goes from obviously not being a separate living individual, to becoming one. Abortion then becomes murder of a living individual at least at the far end of that grey area. Inside the grey area it may or may not be murder - so no one could be convicted of murder beyond a reasonable doubt if they commited an abortion during that period. However, society may wish to err on the side of caution and make abortion inside the grey area a criminal offence.
The arguments about enforcement are irrelevant. Making murder illegal does not stop murder, rather it drives it underground and results in "backstreet" murders, hit men and so on. That does not in any way imply that we should relax the laws on murder, or the enforcement of those laws. The same line of reasoning applies to abortion. If something is a living human being, then it has rights, and ought to be protected by law. If not, then it shouldn't.