adoption

I live in CO. I have a 9 year old son. I am getting married soon and my fiance wants to adopt my son. My sons biological father resides in Ohio as far as I know. He has had no contact with my son in almost 5 years. We have never gone to court for custody and he pays no child support. We have been to court and the father was convicted of felony stalking. I guess the basic question is where do I start. Do I still have to have the biological father sign away his parental rights or is there any type of abandonment clause that comes into play? Any advice would be appreciated.

You only have one year to wait for abandonment. GO to your states statutes and look up "child rights". Your state will have documented what they consider abandonment.
Now after 5 years of no cards, contact, support; you will not need his signature. Set the court date, serve him the papers and explain to him he will be off the hook for an financial responsibility if he does not appear. Other wise he will have to take the stand and explain why the adoption needs his consent and where and why he has been a no show for so many years. Usually the judge blasts the person for their irresponsibility and humiliates them in fornt of whom ever is present. So unless they are gluttens for punishment they 99% of the time stay way away form teh court room.
If you can't find him post a notice of the adoption in a newspaper near him then await for a response. But you did try to inform said "parent" of the adoption.