California Gov. Arnold Schwarzenegger demanded that a convicted killer accused of kidnapping two Idaho children be shipped to his state to be tried for the 1997 slaying of a 10-year-old boy.

But the U.S. attorney's office in Boise insisted Thursday it has custody of Joseph Edward Duncan III. Duncan was charged in Idaho with kidnapping and killing 9-year-old Dylan Groene and kidnapping his sister Shasta Groene, then 8, who was the only survivor of a 2005 attack on the family's home.

Duncan is already in prison after pleading guilty in October in Idaho to kidnapping and killing the children's mother, Brenda Groene; her fiance, Mark McKenzie; and her 13-year-old son Slade.

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Bill Maile, spokesman for Schwarzenegger, said the extradition request was also sent to Idaho Gov. C.L. "Butch" Otter.

"Public safety is Gov. Schwarzenegger's highest priority, and he believes justice must be served in this case," Maile said.

The office of U.S. Attorney Tom Moss said it expects Duncan to remain in Idaho.

"We believe we have custody," said spokeswoman Jean McNeil. "This is a state-to-state matter. It will go through the governor's office, and the attorney general's office, and we are out of the loop."

Jon Hanian, a spokesman for Otter, said late Thursday that the governor had not seen the request. Otter will likely defer to law enforcers in Idaho, including the U.S. attorney, on where Duncan should be prosecuted first, Hanian said.

On April 4, 1997, Anthony Martinez, 10, was forced into a car in Beaumont, Calif. A forest ranger found the boy's nude, bound body 16 days later about 70 miles east. The killing was unsolved until Duncan's 2005 arrest in Idaho, after which California investigators found the man's partial fingerprint on tape used to bind the boy.

Duncan was charged last month in Riverside County, Calif., in the boy's death. Prosecutors have said they intend to seek the death penalty.

Duncan has already pleaded guilty to state charges of first-degree murder and kidnapping in the first three Idaho killings. He was sentenced to life in prison without parole on the three kidnapping counts, but sentencing on the murder counts was deferred while federal charges involving Dylan and Shasta were prepared. Federal prosecutors say they plan to seek the death penalty in Dylan's case.

Shasta was rescued July 2, 2005, at a Coeur d'Alene restaurant where Duncan was arrested.

Duncan, who has spent much of his life behind bars because of a 1980 conviction for raping a 14-year-old boy in Tacoma, Wash., is also suspected of killing two girls in Washington while on parole.

Federal prosecutors say Duncan has acknowledged the Washington and California slayings, though Seattle-area law enforcers contend those statements, made to FBI agents, stopped short of a confession.

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