Inside The Death Of Convicted Serial Killer Joseph Duncan

Joseph Edward Duncan, a serial killer and child molester who was awaiting execution following his conviction for a litany of horrific crimes in 2005 against an Idaho family that includes murder, torture, child molestation, and kidnapping, has died in hospital of brain cancer, aged 58, according to an official statement from the Office of District Attorney for the County of Riverside.

Per the statement, Duncan's death sentence was handed down for the murder of 9-year-old Idaho boy Dylan Groene, whom Duncan kidnapped along with his sister, 8-year-old Shasta Groene, after the brutal slaying of the children's mother, 40-year-old Brenda Groene, her partner, 37-year-old Mark McKenzie, and the family's eldest child, 13-year-old Slade Groene.

Duncan molested and killed Dylan at a cabin in Montana after keeping the children imprisoned for several weeks, according to Newsweek. While he tortured and molested Shasta as well, she was eventually rescued at a Coeur d'Alene Denny's while dining with her captor. Duncan had filmed his abuse of both children, footage that was later used as evidence against him at trial.

After he was taken into custody, he was connected, via DNA evidence, to another murder dating nearly a decade earlier. Anthony Martinez, 10, was murdered while Duncan was on parole stemming from rape charges. 

He later admitted to the slaying of numerous other children over a period of almost a decade.

Joseph Edward Duncan's brain cancer diagnosis

It was first reported that Joseph Duncan had developed brain cancer at the start of March, when, according to KXLY, court filings revealed that he had been given a diagnosis of glioblastoma — terminal brain cancer — back in October 2020. The filings noted: "In November 2020, Bureau of Prisons medical staff determined his life expectancy to be 6 to 12 months... medical staff discussed end-of-life preparations with Mr. Duncan," per the same source. The filings also claimed that Duncan had refused both chemotherapy and radiation therapy, cancer treatments that could have lengthened his life expectancy.

Reactions to Duncan's death from both officials and family members of his victims were unified in arguing that, although the sentence was not carried through as intended, justice has ultimately been done, and that Duncan's death means closure for those he hurt.

Ernesto Martinez, the father of Duncan's victim Anthony Martinez, told KXLY: "While I would've liked to witness his execution, knowing he is now standing before God being held accountable for what he has done, what he did to my son and the horrible crimes he committed to others, that is the real justice." Anthony's mother, Diana, said: "The sun is a little brighter today."

Per Newsweek, Duncan's final appeal against his death sentence in 2019 was denied.