Joe Ridley was a geneticist who conducted research into progeria.
Ridley's research into this fast-aging condition in children led him to believe that the aging process could be slowed, stopped or even reversed. He lobbied for human trials of several drug treatments to slow the aging process but was refused, he then began conducting his own trials secretly on out-patients.
His colleagues were appalled at his cavalier treatment of his progeria patients, seeing them as "a wonderful opportunity" to research the effects of aging, and mockingly referred to him behind his back as "Dr. Mengele" and "Dr. Frankenstein."
The state of Maryland revoked Dr. Ridley's medical license in 1979 for flagrant research practises and misuse of a government grant. After losing his license he was recruited by the U.S. government and given the necessary funds to continue his work, and he performed his experiments on prisoners incarcerated in federal prisons. In 1989 he produced his only successful test subject, convicted bank robber and murderer John Barnett, in whom he successfully managed to reverse the aging process. Ridley also gave Barnett a new right hand that was grown from salamander cells that was much stronger than a normal human hand. Ridley then signed a death certificate for Barnett and released him. Barnett would subsequently steal all of the doctor's work and try to auction it off to the highest bidder in return for money and a full pardon for his crimes.
Ridley would personally reveal many of these details to Mulder and Scully in 1993 after voluntarily approaching them. At the time they interviewed him, he told the agents that he was suffering from a rare vascular disease and had no more than a month left to live, in spite of his youthful appearance. This suggests that he tried, unnsuccessfully, to use his techniques on himself. It is assumed that he died soon after their conversation.