Federal prosecutors are opposing an attempt by serial killer Joseph Duncan's attorneys to question his previous lawyers behind closed doors.

In a response filed late Tuesday in U.S. District Court in Boise, the U.S. Attorney's Office said no reason exists to close the courtroom that overrides the need for an open judicial process. U.S. District Judge Edward Lodge ruled in their favor Thursday morning, rejecting the defense's request.

Michael Burt and Randall Martin, noted anti-death penalty lawyers assigned to defend Duncan, argued in their motion filed Sunday that their client's former attorneys should be allowed to testify in private at his mental competency hearing so as not to jeopardize attorney-client relationships. Those lawyers include Judy Clarke, who's considered the country's top anti-death penalty lawyer. Her most recent high-profile clients include Arizona mass shooter Jared Loughner.

Clarke and the other attorneys who worked with Duncan are concerned how news of their testimony could affect future communications with clients.

But prosecutors pointed out that some of Clarke's communications with Duncan have already been represented at Duncan's competency hearing, which began Jan. 8, and that Duncan's lawyers did not seek to admit the evidence under seal from public view.

Also at issue, prosecutors say, is the public's deep interest in the case, which is Idaho's only federal death penalty case.

"If the public were not allowed to at least hear and see the testimony of former defense team members, the public interest in ensuring the appearance of fairness would be undermined," wrote Wendy Olson, U.S. attorney for Idaho. "The public also may lack confidence in this Court’s decision if part of the proceedings take place in camera, particularly if the Court’s decision relied in part on the in camera proceedings."

Prosecutors say they've already accommodated attorney-client privilege concerns by agreeing to only use Duncan's communication with his attorney as evidence in the competency proceeding, not in the criminal case.

A federal jury in Boise in 2008 gave Duncan three death sentences for the kidnapping, rape and murder of a 9-year-old North Idaho boy, Dylan Groene, after a three week-trial. The five-time convicted killer murdered the boy's brother, mother and mother fiance with a hammer before kidnapping him and his 8-year-old sister, Shasta, who survived.

The 9th Circuit Court of Appeals ruled last year that Lodge should have held a hearing to determine if Duncan was mentally competent when he waived his right to appeal those death sentences. The hearing is expected to last a few more weeks at the federal courthouse in Downtown Boise. It's provided the most detailed look to date on the serial killer and longtime sex offender's mental state. Duncan believes he is competent and has expressed frustrations about his defense attorneys in interviews with FBI investigators and prison psychologists, according to testimony.

It's not the first time the issue of a closed courtroom has come up in the case. Prosecutors sought to close the courtroom during the 2008 trial for Shasta's testimony. Lodge approved the request, despite the opposition of media outlets, but the girl never testified.

Duncan's lawyers say he suffers from religious delusions that make him incompetent to act rationally. They point to, among other things, what Duncan has described as an "epiphany" that stopped him from killing Shasta and prompted him to return her to Coeur d'Alene, where she was rescued and he was arrested. They say he suffers from post-traumatic stress disorder from being abused in prison. They also say he was sexually abused as a child at a youth ranch.

Witnesses for the prosecution include Ada County Jail employees who have said they observed no mental problems with Duncan. Corrections Deputy Amber Jordin testified Wednesday that Duncan was a “model inmate” who was always polite and didn’t pester staff.

Jordin recalled only one request from Duncan that went unfulfilled because of jail policy. He wanted her to give a book to John Delling, the mentally ill man who shot three men - two fatally - during a 2007 two-state crime spree. Delling was housed in a cell next to Duncan until he went to prison to begin serving his life sentences in late 2009.

Burt and Martin have not yet started calling witnesses, but they've implied in cross examination that they believe Duncan sabotaged his own defense based on delusional beliefs about religion and the criminal justice system.

Subpoenas filed by Burt and Martin show they intend to call Duncan's lawyers from his murder case in Kootenai County, Lynn Nelson and John Adams, who is head of the Kootenai County Public Defender's Office.

A woman from Centerville, Ga., Cheri Cox, also has been subpoenaed. Burt confirmed to the Idaho Statesman Wednesday that Cox is Duncan's sister.

If she testifies, Cox will be the first of Duncan's family members to appear in court. His mother lives in Western Washington and has declined to talk to reporters. It's not clear where his father lives, but Duncan told authorities he was considering driving to his father's home and confessing to the 1996 murders of two young girls near Seattle before he went on the crime spree in Idaho.

Duncan cited the death of his brother in a letter to the court last year, saying he was allowing his attorneys to pursue his appeal because he is now his mother's only surviving son.