Notorious Serial Killer Joseph Edward Duncan III Dies of Brain Cancer on Federal Death Row at Age 58

TERRE HAUTE, Indiana — Joseph Edward Duncan III, one of the most notorious serial killers in modern American history, died on July 1, 2026, at the age of 58 while serving a federal death sentence at the United States Penitentiary in Terre Haute.

According to authorities, Duncan succumbed to complications from stage 4 brain cancer. He had been on death row since 2008 following his conviction for a series of horrific crimes that terrorized multiple states and left several families devastated.

Duncan was convicted in federal court for the 2005 murders of Brenda Groene, her son Slade Groene, and her boyfriend Mark McKenzie near Coeur d’Alene, Idaho. He also pleaded guilty to kidnapping and murdering 9-year-old Dylan Groene and kidnapping 8-year-old Shasta Groene, who was later rescued alive from a Denny’s restaurant in Coeur d’Alene on July 3, 2005.

The crimes shocked the nation due to their brutality and the fact that Duncan had previously been released on parole after serving time for a rape conviction in Washington state. He was linked through DNA evidence to the 1997 abduction and murder of 10-year-old Anthony Martinez in California, for which he received two life sentences in state court in 2011. Duncan also admitted to the 1996 murders of two young sisters in Bothell, Washington, though he was never prosecuted for those due to his existing sentences.

U.S. District Judge Edward Lodge imposed the federal death sentence in 2008 after a jury verdict. Duncan had pleaded guilty in 2006 to the Idaho state murders and later in 2007 to the federal charges involving the Groene children.

In statements released following his death, victims’ family members expressed a complex mix of relief and ongoing grief. Anthony Martinez’s mother, Diana, said, “The sun is brighter today, and my soul is lighter. The world is a more beautiful place without the evil that is Joseph Duncan. God chose to make his end a long suffering and I believe that is fitting.”

Anthony’s father, Ernesto, added, “While I would’ve liked to witness his execution, knowing he is now standing before God being held accountable for what he has done… that’s the real justice.”

Acting U.S. Attorney Rafael M. Gonzalez Jr. issued a statement noting the profound impact of Duncan’s crimes on the victims’ families, the community, law enforcement, and all involved in the case. “While his death will not bring back the lives cut so tragically short or remove the indelible memories of his unspeakable acts, perhaps death will now allow space for some degree of healing, peace, and closure,” Gonzalez said.

Duncan’s death marks the end of a long and disturbing chapter in American true crime history. His case drew widespread attention not only for the horrific nature of the offenses but also for the survival story of young Shasta Groene, who provided critical testimony and became a symbol of resilience.

Authorities confirmed that Duncan remained on death row at the time of his death and had been receiving medical care for his advanced cancer in recent months.

The Federal Bureau of Prisons has not released additional details regarding funeral arrangements or the final disposition of his remains, consistent with standard protocol for federal inmates.

This development brings a measure of finality to families who have waited years for justice, even as the pain of their losses remains.