Convicted sex offender Joseph Edward Duncan III, who beat a northern Idaho mother, her fiance and oldest son to death before abducting her two youngest children, pleaded guilty to 10 federal counts Monday in the 2005 kidnapping and slaying of one of the children.

Duncan, who lived in Fargo before his arrest, faces a possible death penalty for the crime, and the sentencing phase of his court case is expected to start Jan. 28.

Duncan told U.S. District Judge Edward Lodge that he wants to take responsibility for his actions.

"I will continue to accept that responsibility to the death," he said.

Duncan did not make a plea deal with prosecutors. He faces a possible death penalty on three of the felonies: kidnapping resulting in death, sexual exploitation of a child resulting in death, and using a firearm during and in relation to a crime of violence resulting in death.

He also pleaded guilty to kidnapping, two counts of aggravated sexual abuse of a minor, being a felon in possession of a firearm, transportation of a stolen firearm, possession of an unregistered firearm, and transportation of a stolen vehicle.

Duncan's plea means that young Shasta Groene, the only survivor of the attack, will be spared the trauma of testifying at his trial. It was not clear if she will be expected to give a victim impact statement for a federal sentencing jury.

Shasta was not in the courtroom Monday. She lives in Coeur d'Alene with her father, Steve Groene, in a home built for them through donations from the community.

In his plea Monday, Duncan admitted kidnapping Shasta, then 8, and her 9-year-old brother, Dylan Groene, from their Coeur d'Alene home in 2005, sexually abusing them and later killing Dylan at a remote Montana campsite. Shasta was rescued about seven weeks after the abduction after people spotted Duncan and the child at a Coeur d'Alene restaurant.

Duncan earlier pleaded guilty in Idaho state court to kidnapping and murdering other members of the Groene family at their home in May 2005. Shasta and Dylan's mother, Brenda Groene; her fiance, Mark McKenzie; and her 13-year-old son, Slade Groene, were bound and bludgeoned to death with a hammer. Prosecutors alleged Duncan killed the three so he could kidnap the younger children for sex.

Duncan was sentenced to life in prison without parole for kidnapping the three older victims. But the state judge deferred imposing punishment on the murder counts to give federal prosecutors time to pursue their case, which is centered on events in Montana after the children were abducted.

Court documents allege Duncan took the two youngest children and drove into the mountains near St. Regis, Mont., where he sexually abused them for weeks before killing Dylan. The boy's body was found in a remote campsite.

Duncan has been quoted in court documents as saying he was trying to return Shasta to her father when he and the little girl were spotted in a Coeur d'Alene restaurant on the morning of July 2, 2005, about seven weeks after the family was attacked.