proof of paternity

Several years ago, while addicted to drugs, my friend failed to answer a paternity request or have a blood test to prove parenthood by Deparment of Family & Children Services. After treatment in a "drug center" he returned to work and was ordered by the courts to pay child support which has been taken out of his check for the past several years. He has gone to several attorneys to check into getting tested for parenthood, but has been given the run around or told that it is not possible. What can he do to request a blood test to prove or disprove parenthood for this child that he thinks is not biologically his?

If he is paying support, then paternity was established with him at some previous point.

If several years have passed, it's too late for him to go in and undo it now, even if he really isn't biologically the dad.

Legally, he IS the dad now.

I can't agree that there is nothing he can do.
My brother was in a relationship with a woman who, after the break-up, found out she was pregnant and gave birth to a baby girl. My brother, being the responsible man he is, made sure he was present during delivery, and believed the mother, that she was his daughter. Shortly after the child was 10 months old, the bio mom played games with visitation and cs, and gave my brother a really rough way to go. After learning that bio mom had a problem with promiscuity, (lots of other sex partners), even before she got pregnant, my brother hired an attorney, and filed a motion to "set aside judgement of paternity, and motion for genetic testing". The judge ruled in his favor, and motion was granted. His daughter was 3 years old at the time. This took place eventhough he signed an acknowledgement of paternity form at the hospital when she was born. (He is in fact the bio dad).
Because of the circumstances with your friend having previous drug problem, and rehabilitating himself at that time, an attorney would be willing to take his case. Keep trying.