Georgia has sort of struck a middle ground here. Each case is decided on its own facts. If the father had no reason to suspect that the child was not his own, and he promptly takes action to disentangle himself as soon as he learns that the child may not be his own, he may do so. On the other hand, if the father does NOT take action as soon as he learns of a potential paternity question, but just lets things slide along (so that the child grows up believing that the man is his daddy) then he may NOT back out of the deal.
For some reason (the price of DNA testing went down?) we have had a fairly large number of these cases in the past 2-3 years, and the results are all over the map, depending on whether the putative father should have been suspicious or whether he took prompt action. Most extreme case was a dad who tried to get out of paying child support when the kid was THIRTEEN! (court concluded he should have known something was up when he married the woman on the rebound from another relationship and she turned up pregnant within days of the marriage. He had a blood test (not DNA test although available) done and claimed he was told that his blood type "proved" the child was his. Trial judge didn't believe this cock-and-bull story, neither did Court of Appeals.)
In other words, if the mother is an excellent LIAR, good at DECEPTION and capable of perpetuating a FRAUD over a great length of time, the male "partner" is on the hook for years and years?
Sorry, but something is wrong with that picture.
It's ridiculous that the issue is seen as one of "balancing" in the first place. If a single parent burglarizes a house to buy toys for a kid, a kid who has done nothing wrong, there is no "balancing" in deciding whether or not the original owners are entitled to their property back. They were wronged in the taking of the property. The thief must return the property or pay the victims for it. It doesn't matter that the theft benefited a kid, that restitution would harm a kid who's done nothing wrong.
Why should the situation be different in the case of fraud? If a man is deceived into thinking that he is the father of a child then there is no good reason for claiming that he still must be on the hook for child support. Even if the child would be "harmed" by the repayment of the funds the man was bilked of, this is not reason to permit the fruits of the mother's fraud to be left alone. Even though the child is innocent, the child will lose money he was never entitled to have, just as if his parents were professional thieves or con-men.
What you describe in Georgia sounds contemptible. The father must prove not only that he didn't know that the child was not his, but that he wasn't in a position where he ought to have known. What the h*ll? In what other fraud case is it a requirement that the plaintiff show not only that he was deceived but that he investigated what clues there were fully enough to ensure that he wasn't being deceived?!
If a child in a supporting relationship turns out to be not the child of the man paying support, the presumption should be that the woman has to show that she did not deceive him into paying support if support is going to continue. Compare: if the computer I sold you turns out to be significantly different than you thought, the presumption should be on me to show that you weren't deceived.
But of course the court will look at these matters differently, in part because children are involved, but also because of the "woman" defense. Yes, she was deceitful, but apparently women have greater legal rights to be deceitful than do men. Men, I suppose, are to be used for providing for illegitimate kids of other men.