Brian David Mitchell can turn his singing and religious persona on and off as he chooses, according to the U.S. Attorney's Office.

In federal prosecutors' latest court filing this week, they once again stated they believed the man accused of kidnapping and sexually assaulting Elizabeth Smart acts differently when he's not the focus of attention, such as during court hearings or when he's being interviewed by medical experts.

"(Mitchell) is tactically derailing and obstructing the court process through concealment, manipulation and, at times, malingering. … (Mitchell) has the ability to cooperate in his defense if he so chooses," prosecutors state in court documents.

The U.S. Attorney's Office responded this week to a motion from the defense seeking to prevent all lay witnesses from testifying during Mitchell's federal competency hearing, scheduled to resume Nov. 30. Smart was allowed to give her testimony early because she will leave on a LDS mission to Paris before the hearing.

A hearing regarding several motions about who will be allowed to testify during the competency hearing was scheduled for Monday.

Prosecutors contend that lay witnesses are important in getting a full picture of Mitchell because many have been around him "with his guard down."

"The more time you are with a person, the more you can tell about things such as their sincerity, interests and shortcomings," prosecutors argue in court documents. "Lay-witness testimony is highly relevant to determine (Mitchell's) present mental condition."

The U.S. Attorney's Office is expected to argue lay witnesses' testimony is also relevant because Mitchell's mental state has remained relatively unchanged for years.

Witnesses from the Utah State Hospital were expected to testify that "the person they saw leave the hospital on Oct. 20, 2008, (when Mitchell was transferred to the federal system) was the same person who entered on Aug. 11, 2005 (when Mitchell was declared incompetent to stand trial)," court documents state.

One Utah State Hospital employee is expected to testify that Mitchell once stated, "I sing to disrupt the system so that I can come back to the hospital," according to court documents. Another staff member heard him saying, "If people think you're crazy, you can get away with more."

The witnesses will also testify how Mitchell has lied in other situations, including to his now-estranged wife and codefendant, Wanda Barzee, and officials in Lakeside, Calif.

In more examples, prosecutors say Mitchell attempts to take control of interviews conducted by medical experts attempting psychological evaluations, and to manipulate the proceedings.

During an attempted interview by Dr. Michael Welner, the government's key witness, he said that Mitchell kept his eyes shut and would not speak to him from the moment he walked in the room, "but opened his eyes when a video of Elizabeth Smart's interview was played, demonstrating he is fully aware of his surroundings and selectively chooses when he wants to participate," according to court records.

Prosecutors were also expected to use lay testimony to show that what drove Mitchell was sex and not religion. One of his biggest preoccupations at the State Hospital, according to witnesses, was the TV show "Charmed," which prosecutors said featured "scantily clad young girls."

"(Mitchell) watched the show for hours each day and would sit close to the television," the court documents state.

He would also read books, watch movies and speak "at length about topics ranging from politics to literature."

e-mail: preavy@desnews.com