Mens rea in hypothetical "illegal" abortion

Question

Consider the following hypothetical scenario. I recognise that it very likely to never occur, but I am interested more in the technical implications than in any actual possibility. Additionally, while the ethical questions involved are certainly interesting, I am specifically asking about the actual legal issues involved, not about the ethics of the situation (except so far as they might apply to the legal outcome).

A clause is added to the constitution declaring unambiguously that all unborn foetuses fitting a certain set of criteria are human beings with all the attendant basic rights etc.

A pregnant woman, whose unborn child matches the set of criteria exactly, but who absolutely, unequivocally and unambiguously believes that her unborn foetus is not a human being, procures an abortion.

Is the woman legally guilty of murder (or, if not, any form of homicide)?

I'm interested in any and all reasons for the answer being yes or no, but my main concern is the following:

The act of procuring an abortion, as I understand it, would satisfy the actus reus of murder, that is, the deliberate ending of a human life. However, if someone is genuinely convinced that they are not killing a human being (which includes the circumstance that what they are killing is not a human being), it would seem that they do not satisfy the requirement for mens rea for a murder conviction.

One might draw a parallel with a woman with postpartum psychosis who, while hallucinating that her six-month-old son is a monster, throws him from the balcony of an apartment building, killing him. In both cases, the woman involved causes the death of her child, but is totally convinced that she is not killing a human being.

Answer 1

Yes the woman is guilty of murder (under the law OP described)

The issue of common law mens rea (the guilty conscience) is moot as it is no longer a component of the crime, see here.

Almost all jurisdictions today have codified crimes so the common law mens rea is not relevant, for example, in Texas a person commits murder if they "intentionally or knowingly causes the death of an individual"; feeling guilty about it or knowing it was wrong is not an issue.

In the facts you describe the person "intentionally or knowingly causes the death of an individual"; the fact that she did not consider the victim to be a person is immaterial. As described, she would have a hard time with an insanity plea in the same way that a white supremacist murderer would for classifying members of other races as "non-persons".

You can see why the common law usage would no longer work.

Answer 2

A clause is added to the constitution declaring unambiguously that all unborn foetuses fitting a certain set of criteria are human beings with all the attendant basic rights etc.
A pregnant woman, whose unborn child matches the set of criteria exactly, but who absolutely, unequivocally and unambiguously believes that her unborn foetus is not a human being, procures an abortion.

Under those circumstances, the woman would be guilty. Although mistake of fact is a defense for most crimes, this is actually a mistake of law, which is not a defense.

There was a somewhat ridiculed case in which a court decided that a bee was legally a fish for the purposes of a particular law. But the court wasn't wrong; the law literally defined invertebrates as fish. Honestly believing that bees are not fish would not save you if you violated such a law in regards to a bee. It doesn't even matter that you are correct that a bee is not really a fish; you're still guilty. The law is allowed to have ridiculous definitions, and you still have to abide by those definitions. The definition (from that case) in question reads:

“ ‘[f]ish’ means a wild fish, mollusk, crustacean, invertebrate, amphibian, or part, spawn, or ovum of any of those animals.” (Stats. 2015, ch. 154, § 5.)

So, it doesn't matter that the woman honestly believes that the unborn is not a human being. She knows (or should know) that the law unambiguously considers it to be a human being.

If the woman believed that what she was destroying was not only not a human being but not an unborn foetus, however, that would be a mistake of fact and she likely would not have the required intent. (For example, if the doctors lied and told her that it was a tumor, and she believed them, she wouldn't be criminally liable for having it removed.)