Tl;dr they'll probably use it and its a weak excuse in front of a judge, thus making themselves looked like an idiot and FMC's innocence should be 100% guaranteed if they do use it.
@Paulthetic they must've known that their marriage is only officially acknowledged the day after the 'murder' incident. I'll assume that there's no law that hinders women rights.
The reason I assumed that is because in an earlier chapter, Raven states that there's no written law that said about a woman doesn't have the right to heir. Although it is stupid of me to do this, I decided to just assume women rights are hindered not because of the law, but because of the sickening and deeply rooted prejudice.
So to use that bullshit excuse in an official setting like this is... well, bullshit. I do agree with you that they'll probably use it. If they do, then FMC's innocence should be 100% guaranteed... should be.