The mother is not-quite-17 and gets involved in a summer romance with someone who is 21 or 22. She discovers she is pregnant, and both of them want to have the child, but her parents want him prosecuted for statutory rape (mostly out of prejudice, actually; one of her older sisters got into a similar fix and quietly got married, but in this case the father-to-be is of a different race, so her parents don't consider that acceptable) and they file charges against him. [EDIT: Yes, I have looked at New York laws, and this degree of age difference would constitute third-degree rape.]
For the story to work as I currently intend it to, the father needs to end up imprisoned (or at least under orders to have no contact with the mother and child) and the mother needs to be able to leave home and have the child (her parents kick her out), without losing custody.
So...approximately how would this work in, say, 1983, in smallish-town upstate New York?
Next question: the father is very bright and determined to make the most of his life despite what has happened. He was also very much in love with the mother and never really got over her, so he's going to be throwing himself into his work as a way of forgetting. Would it be at all realistic for him to become a college professor despite his criminal record? (There is nothing at all else on it, and he was a model prisoner/probationer.)
What other obstacles might be thrown in the way of him building a relationship with his daughter? I'm hoping for them to have some kind of reunion when she's in high school, and for him to have been prevented for some reason or other from doing so sooner. It doesn't directly have to relate to the criminal charges (though specific to this, he should not be actually paying child support; he's been putting the money in a savings account the whole time, but it doesn't reach the mother and child).