The central Florida man is serving time for aggravated child abuse. He was convicted of the crime after he and his wife brought their infant son Kody to the emergency room when they noticed he was in pain and not using the left side of his body. The doctor found 13 broken bones and a skull fracture in his X-rays, but no bruises. He called the police.
"I am innocent," Duncan told CNN's Jean Casarez. "I did not harm my son."
The case's prosecutors are standing by the conviction, but Duncan is hoping a new lawyer, and new medical science, will end his nightmare and bring him home. His lawyer is taking his case to the 2nd District Court of Appeals in Florida next week, and he is hoping for a new trial.
Duncan and several of his family members sat down with CNN to tell his story.
"All I could think about was, 'Oh, my God, he's gonna die in there and never see his kids,'" said his mother, Celeste Bonnell.
So far, she has been right. His two boys, Kevin and Kody, are now men in their 20s. Kody's bones healed, and he believes his father was wrongly convicted.
"I never once had a doubt that he hurt me. I don't believe it." Kody said.
Besides the X-rays and testimony from Florida pediatrician Dr. Mark Morris, who stands by what he said, there was not much evidence. One witness, Duncan's wife's grandmother, said she saw him harm his son, but she later recanted and her statement was not used in the case. There was also an incident when a child began vomiting after Duncan watched her, but authorities concluded that in that case, child abuse was "unfounded."
Now, more than 20 years later, Illinois radiologist Dr. David Ayoub said he believes Kody had infantile rickets, a disease of early life in which bones do not mineralize properly. Ayoub said he believes this led Koby to develop metabolic bone disease, causing Kody's bones to be very fragile. With that diagnosis, Florida Defense Attorney Lisabeth Fryer is working to get Duncan's conviction overturned.
The family is hopeful. Kody has not seen his father, and only knows him from two phone calls a week, because in the eyes of the law, he's seen as the victim of Duncan's crime.
"I wish I could talk to him in person," he said. "I just wish I could see my dad."