Donald Henry Gaskins
In 1969, Gaskins began killing a series of hitchhikers he picked up while driving around the coastal highways of the American South, torturing and mutilating his victims. He claimed to have killed eighty to ninety people. He was arrested in 1975, when a criminal associate confessed to police that he had witnessed Gaskins killing two young men. He was convicted of 8 murders and was sentenced to death which was later commuted to life imprisonment without parole. Remarkably Gaskins went on to commit a further murder within the high security prison, killing a fellow inmate. He is the only man to have ever killed an inmate on death row.