Men who signed the birth certificate because you believed you were the Dad, but found out later that you were not, what happened, and did you get your name removed?

I ran into a former co-worker while Christmas shopping and we were working together he was in the middle of a nasty legal battle. He found out he was not the father of his long-term gf baby. He had signed the birth certificate, thinking he was. I asked him what happened with that, and he said it took time and money, but he was able to be removed and not liable for child support. He said he had a good lawyer and a sympathetic judge, but it was still quite a process. I was wondering what the stories of other men who were in this situation were?