Lawyers for a Pakistani scientist accused of shooting at U.S. Army personnel in Afghanistan asked a judge Tuesday to stop her from testifying, saying her "diminished capacity" would result in a "painful spectacle indeed."

Lawyers for Aafia Siddiqui said verbally and in a letter to Judge Richard M. Berman that the 37-year-old Pakistani scientist should not be allowed to testify when the defense case begins Wednesday despite her repeated stated desire to do so.

Prosecutors declined to immediately comment on their opinion regarding the request.

Siddiqui's trial, which began with opening statements last week, has featured repeated outbursts by Siddiqui in which she decries the court proceedings as unfair and challenges the testimony of government witnesses. She has been escorted from court several times.

Siddiqui's lawyers said there is precedent for denying the right to testify to a defendant who has been disruptive in court and who intends to testify about issues that are not relevant to the charges.

The lawyers wrote that their client's desire to testify "are driven by an irrational and delusional belief that she can convince listeners that she can bring world peace."

In a footnote, they said their conversations with her regarding what she would talk about if she testifies show that her perceived ability "to bring world peace, especially between the United States and the Taliban, appears to be the primary, if not sole, topic."

Siddiqui is on trial on charges that she attempted to murder U.S. Army officers and FBI agents in an Afghan police station in July 2008 by picking up a rifle and firing it as she was about to be questioned.

U.S. authorities say it happened as she was about to be questioned after she was caught a day earlier carrying handwritten notes referencing a "mass casualty attack" and listing the Brooklyn Bridge, Statue of Liberty and other New York City landmarks.

Months ago, lawyers for Siddiqui attempted to have her declared incompetent to stand trial, but Berman rejected the request after several psychologists concluded that she was faking mental illness.

During her trial, Siddiqui frequently drops her head on the defense table as if she is asleep as jurors are brought into the courtroom. She is quickly ushered out of court after each of her outbursts. Sometimes, she asserts her innocence. At other times, she challenges evidence.

Just before lunch Wednesday, she announced: "That's it. I'm going to boycott from now on. I'm not coming here again."

She did not return.

In the letter to Berman, her lawyers said allowing Siddiqui to testify would undermine the trial's fairness.

"Due to her severe mental illness, Dr. Siddiqui is unable to confer constructively with her attorneys," they said, adding that she has refused to speak with them since they urged her not to testify.

"Not only is she subjecting herself to all of the dangers of cross-examination, she risks prejudicing herself in the eyes of the jurors should she repeatedly underscore her ability to reach out to the Taliban in order to broker peace between that group and the United States," the lawyers wrote.

They said her "irrational and bewildering insistence that she has the power to influence the Taliban" will invite jurors to infer she has terrorist associations.

"On that basis they very well may convict her," they wrote.

They also said Siddiqui's family has found it painful to watch the defendant in her unstable mental state.

"Should she take the stand and thereby be invited to engage in these irrational and delusional outbursts without constraint, the court proceedings would turn into a painful spectacle indeed," the lawyers said.