Krajcir was born in Pennsylvania around 1944 and served in the navy. He had a conviction for rape in Illinois from 1963 and spent much of the following decade in and out of custody, including a period in a state hospital as a sexually dangerous person. He was released in 1972 and settled in Carbondale, Illinois, where he studied at the university and worked as a security guard.
Between 1977 and 1982 he raped and killed nine women in Cape Girardeau and elsewhere in Missouri, in southern Illinois, and in Kentucky. He entered their houses at night, often having watched them for some time, and shot or strangled them. He was in custody again from 1983 on a rape conviction and remained in Illinois prisons for the next twenty-four years, during which none of the murders was connected to him.
In 2007 the Cape Girardeau police, working cold cases with DNA, matched him to the 1977 killing of Mary Parsh and her daughter Brenda. Confronted in prison in August 2007, he confessed at length and over several sessions to nine murders in four states, giving detail that was verified against the files.
He pleaded guilty and received life sentences in Missouri and in Illinois in 2008, avoiding the death penalty in exchange for the confessions. The case is a standard example in American cold-case work of a man whose crimes were solved only because he was already in prison for something else, and of what the DNA backlog cost: the murders were closed twenty-five years after the last of them, by a man who had been in state custody for the whole intervening period.