Zella Strickland

Joseph Duncan in federal court.

BOISE, Idaho - A federal jury begun deliberating the fate of convicted child killer Joseph Edward Duncan III on Wednesday after he declined to plead for his life.

"This defendant is dangerous. He is a predator who takes pride in his work," Assistant U.S. Attorney Traci Whelan said. "He earned this day. His actions ... call out for the death penalty."

Duncan, who pleaded guilty in December to 10 federal charges involving the kidnapping of two northern Idaho children and the murder of one of them in May 2005, offered no response to prosecutors' call for his death.

"I have no argument," he told the court. Duncan is representing himself.

In closing arguments, Whelan reminded the jury of Duncan's lifelong "pattern of violence."

His past is littered with arrests and prison time, including a conviction for raping a boy at gunpoint in 1980. Duncan has told investigators he killed of two half-sisters from Seattle in 1996 slayings, and he is charged with killing a young boy in Riverside County, Calif., in 1997.

More than three years ago he came to Idaho, stalked a family and entered their Coeur d'Alene-area home, fatally bludgeoning 13-year-old Slade Groene, his mother, Brenda Groene, and her fiance, Mark McKenzie. He then kidnapped two younger children, 9-year-old Dylan and his then-8-year-old sister Shasta Groene.

Duncan pleaded guilty to the killings at the house in state court in 2006.

In January 2007 he was charged with 10 federal felonies involving Dylan and Shasta, who were threatened, sexually abused and tortured before Dylan was killed at a remote western Montana campsite. Duncan subsequently returned with Shasta to Coeur d'Alene, where a waitress recognized them eating in a Denny's restaurant and called police.

The jurors were asked to decide whether Duncan should be sentenced to life in prison without parole or be executed for three of the 10 federal charges: Kidnapping resulting in death, sexual exploitation resulting in death and use of a firearm in a crime of violence resulting in death. U.S. District Judge Edward J. Lodge is bound by their decision.

After the federal case is over, Duncan is expected to be sent to Riverside County, Calif. to stand trial for the 1997 murder of Anthony Martinez.

Each day in the two-week long death penalty hearing unveiled a new layer of horror. The jury was shown a video that Duncan made of himself sexually abusing, torturing and hanging Dylan until the boy lost consciousness.

The heinousness of the evidence in the case will make it particularly difficult for the jurors to remain impartial as they deliberate, said Art Patterson, a jury consultant and senior vice president of the trial consulting firm DecisionQuest.

"Generally, for human beings, it's pretty hard to maintain impartiality when confronted with such horror," Patterson said. "They can say as much as they want, 'My duty as a juror is to be fair and impartial' but they're human beings -- they're not computers. The absolute depravity of what occurred there has to have a biasing effect."

Patterson said he anticipates a death penalty verdict, especially since Duncan failed to offer any mitigation.

"How could any juror not want to see this person removed from our list of living human beings? How could you live with yourself as a juror if there's any chance this human being could escape from jail and do something like this again," he said.

Whelan told the jury that Duncan would pose a risk even to prison guards and fellow inmates.

"This defendant uses the time that he has to think out these plans and he is dangerous," she said. "He is adaptable and he is dangerous."