WASHINGTON – The federal judge hearing the death penalty trial of Zacarias Moussaoui ruled yesterday that federal prosecutors could go forward with their case for capital punishment, but without crucial testimony from aviation officials who were improperly coached by a government lawyer.

The judge later announced a postponement of the trial until Monday, at the prosecution’s request, to allow time to consider appealing her decision to exclude several witnesses.

A notice posted on the court’s Web site said the court granted a prosecution request to delay resumption of Moussaoui’s penalty trial until March 20 at 9:30 a.m. and that no other court sessions are scheduled until then.

After a hearing in which the aviation officials appeared in the absence of the jury, U.S. District Judge Leonie Brinkema said Federal Aviation Administration and Transportation Security Administration witnesses who had been coached would not be allowed to testify before the jury and that she would bar evidence from them.

Although she allowed the trial to continue, the ruling dealt a serious blow to the prosecution, which considered the aviation officials’ testimony crucial to its case.

The ruling came after Judge Brinkema heard from a succession of aviation officials who denied that coaching by a Transportation Security Administration lawyer, Carla J. Martin, would affect their testimony. During their appearances, however, the officials revealed several other apparent misdeeds in the government’s preparations for the trial.

Earlier, Ms. Martin took the witness stand and, faced with possible legal sanctions herself, told the judge she wanted an attorney.

Ms. Martin and half a dozen aviation officials appeared at the hearing called by Judge Brinkema to determine whether she should throw out the death penalty for Moussaoui because of improper coaching of seven witnesses by Ms. Martin.

Ms. Martin, the first to take the stand yesterday, asked permission to address the court and was immediately cut off by an irritated Judge Brinkema, who told her, “No, you’re a witness.”

When prosecutor David Novak suggested that Ms. Martin be advised of her rights, Judge Brinkema told her that she has the right not to testify, that her testimony could be used against her because she is in jeopardy for the alleged violation of a court order and that she has the right to be represented by counsel.

Ms. Martin said she was in “an adversarial proceeding” and wanted a lawyer. She said she spoke to an attorney Monday night, but that he was unable to come to the court yesterday morning. At that point, Ms. Brinkema directed her to contact the lawyer and see if he could come in later yesterday or, if not, at 8:30 a.m. today.

Moussaoui, an avowed Al Qaeda member, is the only person charged in America with involvement in the September 11, 2001, terrorist attacks. He has pleaded guilty to six counts related to the attacks, and federal prosecutors are trying to persuade a jury in Northern Virginia is to sentence him to death.

The witnesses whose testimony Judge Brinkema barred yesterday had been expected to testify about what the government might have done to boost airport security if Moussaoui had confessed his knowledge of the September 11 plot when he was arrested on an immigration charge in August 2001. Originally, three aviation witnesses had been scheduled to testify for the government and four for the defense.

The ruling was seen as a severe blow to the government because the crux of its argument for execution is that if Moussaoui had not lied to the FBI, the attacks could have been prevented. Assistant U.S. Attorney Novak said in court Monday that the testimony of the contacted witnesses constituted “half the evidence in this case.”

On Monday, Judge Brinkema halted the trial and threatened to remove the death penalty as a possible sentence on grounds that Ms. Martin, a veteran government aviation lawyer, improperly shared testimony and communicated with the witnesses.