With a decent lawyer, your son shouldn't have much problem ditching that case. If they were never married AND DNA proves he isn't the father, then a good lawyer shouldn't have a problem popping holes in the case.
If your son knows who the bio dad is, you can request that the court properly reassign paternity. If you don't, the trick is to stay consistent. Put together a war chest and make it clear to the mother that you're going to make her life a legal hell. Sue her in civil courts for fraud too...if he signed under the impression that they were to be married, you can make the argument that she deceived him into signing a legal contract under false pretenses. Either way, the goal is to make sure her legal bills exceed her child support payment, which will eventually force her to give it up.
Don't be afraid to sling mud. Hell, rent a bulldozer for it. I had a friend who's wife slept around on him and got knocked up by another guy. He hired two PI's and collected so much garbage on her that by the time the courts were through she'd not only lost her support case, but the court stripped her of custody of her two older children from a previous marriage. He completely destroyed her life (and that's a good thing...she was a b*#$%).
I've just got to say if some men would stop trying to meet and have sex with women they meet in strip clubs, or women that drink or do drugs as heavy as they do, or women that have as loose morals as they do, then marriage and children would not be a problem....
if you shack up with a drunk, a druggie, a cheap trashy "looker" ....which is why men go after them....then what do you expect them to turn out to be?.....
you can't change men and you can't change women.....
In some states (Massachusetts being one),when you're in
this kind of situation it's not the guy and the gal that go at it in court,it's the guy and the state.So the thought
of wearing her down probably wouldn't work.