How to get DNA test after paternity established

m trying to help a friend with his situation. He has a 12 yr old daughter and has paid support this whole time. She was conceived days before he was incarcerated for a yr in jail. I don't know the exact reasoning but his ex never let him see his daughter and he never tried to push it until now. But now he is questioning if he is the biological father cuz now friends are finally coming to him saying good chance he's not and she got pregnant while he was in jj wil. Even tho he is on the birth certificate, is there a way to get a court order paternity test done since now he is questioning if she is his?