BOISE - Attorneys for convicted murderer Joseph Duncan say their client has a delusional belief system that rendered him incompetent to waive his right to appeal a federal death sentence.

Duncan, who was sentenced to death in 2008 after pleading guilty to kidnapping and torturing two North Idaho children before killing one of them in western Montana, was back in Boise's U.S. District Court Tuesday for a competency hearing.

The hearing, which was ordered by the 9th U.S. Circuit Court of Appeals, is intended to determine whether Duncan was mentally competent when he waived his right to appeal his sentence in 2008.

Defense attorney Michael Burt told U.S. District Judge Edward Lodge that experts will testify that Duncan has a medical condition called brain impairment, which may have caused psychosis and other mental problems. They say that for years, Duncan has held a delusional belief system based on an epiphany that he should not participate in his own defense.

But Assistant U.S. Attorney Justin Whatcott told the judge that the evidence will show that multiple experts and three judges in three different courtrooms all have found Duncan to be competent, and that Duncan himself has consistently demonstrated an ability to make rational decisions.

Duncan has been convicted of five different murders in Idaho, Montana and California. But this competency hearing focuses only on the crimes he committed against young Dylan Groene and his 8-year-old sister, Shasta, in 2005.

Federal prosecutors spent much of the morning eliciting testimony from retired FBI agent Mike Gneckow, who was one of the lead investigators in the Idaho murder and kidnapping cases. Gneckow's wife, Gail Gneckow, is also an FBI agent who worked on the cases, and together they interviewed Duncan multiple times.

It was during those recorded interviews that Duncan talked about his motive for killing, how he chose his targets, and frequently, how he believes that his own death sentence is a greater societal wrong than the torture, kidnapping and murders committed against the Groene family.

Duncan is extremely intelligent and wanted to strike back at society and the criminal justice system for perceived wrongs, Mike Gneckow said.

"He was locked up as a kid, so he wanted to get revenge against society for his lost innocence ... and he chose the method that he thought would cause the most pain against society and that was kids," Gneckow said.

"He essentially said that the criminal justice system is evil, that the criminal justice system is to blame for what he did. He consistently said throughout the interviews that he takes responsibility for what he did but he doesn't take the blame ... the blame rests squarely on society and the criminal justice system," Gneckow recounted.

Duncan frequently talked about what he called his "epiphany," Gneckow said.

Prosecutors played excerpts of that recorded interview, in which Duncan said he had an epiphany while in the Montana wilderness with Shasta Groene, realizing that he was the one making bad choices, the one that was "screwed up."

"I looked at her, and I says, I figured out that's where I want to be, where she is," Duncan said in the recorded interview. "I'm putting myself in her shoes, figuratively and literally in a lot of different ways ... I don't want to idolize her, she's just a little girl, but that's how I want to be, that little girl, like that child."

The goal was to hurt society as much as possible, Duncan said in the interview with the Gneckows, and he said his own death sentence was the greater wrong because it will be carried out by all of society, not just one person.

"To me, it's more important that you guys realize that I was determined to hurt you, to hurt society. I didn't care about the sex. I didn't care about the violence," Duncan said during another excerpt of the recorded interview. "I hated what I was doing but to be hurting you was worth it ... it's very, very human what I did."

During cross-examination, defense attorney Michael Burt focused on other excerpts from the interviews between the Gneckows and Duncan, including one portion where Duncan described praying or talking to the moon one night in Missouri - before he came to Idaho - as he wrestled over whether he should turn himself in for two murders committed years earlier in Washington state or continue on his crime spree.

Duncan said that he subsequently found a gun in a turkey shack and considered it a message from God that he shouldn't turn himself in after all. He continued with his plan, and ultimately used the gun for his crimes in Idaho.

Burt characterized that statement as Duncan literally thinking he heard the voice of God, but Gneckow disagreed, saying he understood Duncan was essentially using a figure of speech.

Defense attorneys said they would call on Duncan's preview defense teams to testify - a dicey proposition since normally any communication between attorneys and their clients are protected from ever being revealed in court under the attorney-client privilege law. If the attorneys do testify, they won't necessarily get to pick and choose which details they share with the court, because talking about one part of their communications with Duncan could open the door for prosecutors to ask them about other communications with the defendant.

Burt said he would seek to have that testimony given in the judge's chambers or in a closed courtroom, because he said it might prompt other clients to worry that someday their private communications with their attorneys would be fodder in court.