SAN FRANCISCO (AP) — A federal appeals court has affirmed the mental competency of a man sentenced to die for kidnapping, torturing and murdering an Idaho boy in 2005.

Joseph Edward Duncan III was convicted of killing several members of a Coeur d’Alene family before snatching their two young children. He also was convicted of torturing and killing a 10-year-old California boy.

Prosecutors said Duncan took the children to the wilderness in Montana where he tortured and abused them for weeks before killing Dylan Groene, 9, and returning with 8-year-old Shasta Groene to Idaho, where he was captured.

When he was sentenced to death in the case, Duncan, who opted to represent himself, waived his right to an appeal.

But he later changed his mind, and the 9th U.S. Circuit Court of Appeals ordered the federal judge in the case to hold a hearing to see if Duncan was competent when he gave up the right to challenge his sentence.

The judge ruled in December 2013 that Duncan was sound enough to understand his legal options, and an appeals court panel affirmed on Friday that Duncan “validly and affirmatively” waived his right to file an appeal.

“His decision to withdraw that waiver, which he made more than two years later, came too late,” the ruling said.

Duncan can ask the appeals court to review the decision and appeal to the U.S. Supreme Court. The ruling opens the door for the first federal execution in more than a decade.

Duncan has also been sentenced to two life terms in California state court for torturing and killing 10-year-old Anthony Martinez in 1997. Duncan abducted Martinez as the child played near his Beaumont, California, home. Duncan confessed to the crime after the Idaho convictions.

Prosecutors in Kootenai County, Idaho have a plea deal in place that allows Duncan to be returned to Idaho to face the death penalty if he isn’t executed federally.

Duncan, a convicted pedophile originally from Tacoma, Washington, has also told investigators that he killed 11-year-old Sammiejo White and her 9-year-old half-sister, Carmen Cubias, near Seattle in 1996. He has never been charged in their deaths.