Shasta Groene remembered it all and has been providing authorities with details that are building a strong case against Duncan.
Duncan appeared before a judge during a brief hearing Wednesday. CBS News reports that the repeat child molester lowered his head and seemed to quiver as charges were read against him.
Duncan was charged Tuesday with three counts of first-degree murder and three counts of first-degree kidnapping in the deaths of Shasta's mother Brenda Groene, 40, her brother Slade, 13, and Groene's boyfriend Mark McKenzie, 37. If convicted, he could face the death penalty.
"He told her he was out driving around looking for children to kidnap," Kootenai County sheriff's detective Brad Maskell testified during a probable cause hearing. "He ... saw her playing in the yard with her brother and wearing a bathing suit. At that point he chose them as possible kidnap victims."
Public defender John Adams declined to comment after the hearing. "We try to do our litigation in the courtroom," he said.
Shasta's ordeal began when she heard her mother call her into the living room early on the morning of May 16. Her mother, brother and McKenzie were bound with zip-ties and duct tape.
Duncan then bound her and Dylan and left them on the ground outside near a swing set. Shasta said she heard McKenzie yell out several times, and at one point they saw Slade stagger, incoherent and bleeding profusely from the head, out of the home. The children yelled for Slade to untie them, but he was unable to respond.
Shasta remembered that Duncan wore dark gloves and had a shotgun and night-vision goggles. She also recalled the brand name of the hammer used to bludgeon the victims, which Duncan showed her after the attacks.
During weeks of captivity at a remote campsite in western Montana, Duncan told Shasta that he cased the family's home for two to three days, using his goggles to look in the windows and study the family's habits and the layout.
"Shasta was very specific that Mr. Duncan is the only person responsible for these acts," Maskell added.
Shasta was rescued early in the morning of July 2, when employees at a Denny's restaurant in Coeur d'Alene recognized her and called police. She has since been reunited with her father.
Dylan was found dead in Montana last week.
Duncan had been charged with kidnapping Shasta and Dylan, but those state charges will be dismissed and instead handled by the federal court system because the youngsters were taken across a state line, authorities said.
Officials have alleged that the children were repeatedly sexually molested during their ordeal, and sheriff Rocky Watson has said he believes the motive for the killings was to acquire the children for sex.
Duncan was freed earlier this year on $15,000 bail after he was charged with molesting a 6-year-old boy in Minnesota. The judge in that case has said he's not sure he knew when he set bail that Duncan was a high-risk "Level III" sex offender who had spent more than a decade in prison for sexually assaulting a 14-year-old boy at gunpoint in Tacoma, Wash.
Police in Fargo, N.D., where Duncan lived, had been looking for him since he failed to check in with a probation agent there in May.
After learning of Duncan's police record, Steve Groene, the father of the kidnapped and murdered children, asked the public to call on their elected officials to prevent Level Three sex offenders from being allowed out in public.
Outrage over the Groene kidnappings and murders is already spurring Idaho lawmakers into drafting plans to strengthen the state's sex offender classification system. They also may establish group homes for convicted molesters, allow judges to order lifetime probation and monitor offenders' movement with Global Positioning System satellites.
"My understanding is that the recidivism rate is so high, in my mind, once they've offended, they've lost all rights in society," Idaho state Rep. Frank Henderson told the Coeur d'Alene Press. "We can't afford to have them on the loose."
"We can put electronic chips in wolves and we have OnStar for when the car goes over the cliff, but we can't follow the movements of sex offenders?" Henderson said. "It's ridiculous."
Coeur d'Alene City Attorney Mike Gridley is investigating whether the city can ban convicted sex offenders from living close to schools, parks, day-care facilities and churches after they are released.
Thomas Hearn, chairman of the Idaho Sex Offender Classification Board, said Washington state's three-level classification system may be used as a model for Idaho, since it has withstood court challenges.
Idaho may also copy Washington's lifetime parole and-or probation law for sex offenders, which went into effect in 2001. Hearn said lawmakers will have to decide whether sex offenders who have already been released could be re-sentenced, and how to pay for the additional supervision.
"What you're talking about is hiring probation officers who are going to keep an eye on a group for a long time," he said. "People need to be aware these things come with a pricetag."
Hearn said he also is urging lawmakers to reconsider past opposition to group housing for sex offenders.
"I, frankly, would rather have them all in one place where you can keep an eye on them," he said.