CBS News 48 Hours examines the case of Kenneth McDuff, a man who was given an extra chance and used it to kill again. In 1966 McDuff, then 20, brutally murdered three innocent teenagers in his hometown of Rosebud, Texas. He was caught, convicted and... (more) sentenced to death. But McDuff got lucky, with dire consequences for others. First, in 1972, the Supreme Court declared capital punishment unconstitutional, sparing McDuff. Then, in 1989, McDuff was paroled from prison. He returned to Rosebud. After he pulled a knife on someone, he was sent back to prison. He was paroled once more. This time he went on to kill at least two others: Between late 1991 and early 1992, he kidnapped and killed two young women, Colleen Reed and Melissa Ann Northrup. He was convicted of the latter crime in 1993 and was sentenced to death. Authorities suspect that he may have killed as many as 14 other women as well. In November 1998, McDuff was executed by injection in Huntsville, Texas. His last words: "I'm ready to be released. Release me." But the question remains: Why was he ever let out?