I did a little research on this type of case. Because a new person is created, a major complication enters the picture. The judges cannot only consider justice between the man & woman, but must also insure the welfare of the child. In these "bait & get impregnated" cases (where a woman deceives a man into leaving his seed vunerable, impregnates herself and suits for child-support), most judges would rule in favor of the duped father and penalize the woman. However, children's rights & needs are prioritized above those of the parents. Thus, unless the mother is relatively wealthy, (assuming the child remains with the mother) if the judge rules in favor of father, the child will not be adequately provided for. It is assumed that the mother definitely wants to be a parent, or else she wouldn't steal the sperm to begin with. In these situations the father cannot be made to unwillingly raise the child he didn't willingly create. But the child's provisions must be delivered. Our legal system just doesn't currently have a way to correctly provide justice for all 3 parties.
I believe the best case scenario is one where the father decides he wants to raise the kid, like MaxPower described.
