WASHINGTON – A federal judge indicated yesterday that she might throw out the death penalty case against September 11 conspirator Zacarias Moussaoui after prosecutors disclosed that a government attorney had violated the court’s rules about discussing witness testimony.

U.S. District Judge Leonie Brinkema called it “the most egregious violation of the court’s rules on witnesses” she had seen “in all the years I’ve been on the bench.”

Her comments came after prosecutors said a Federal Aviation Administration attorney had discussed the testimony of FAA witnesses with them before they took the stand and also arranged for them to read a transcript of the government’s opening statement in the case. Both actions were banned by the judge in a pre-trial order.

Defense attorneys immediately urged Judge Brinkema to throw out the death penalty as a possible punishment for Moussaoui and sentence him to life in prison. Moussaoui pleaded guilty last April to conspiring with Al Qaeda in the September 11, 2001, terrorist attacks. He is the only person convicted in America on charges stemming from September 11. Since last week, a jury has been hearing testimony about whether he should be sentenced to death.

“This is not going to be a fair trial anymore, your honor, because of what a lawyer did in an absolute abrogation of your rules,” said defense lawyer Edward MacMahon Jr. “Showing transcripts to one of the key government witnesses was an obvious attempt to shape their testimony.”

Assistant U.S. Attorney David Novak agreed that the actions of the attorney, whose full name had not been disclosed, were “horrendously wrong.” He indicated that the discussions the attorney had with FAA witnesses concerned whether the government could have stopped September 11, through heightened airport security, if Moussaoui had confessed his knowledge of the plot when he was arrested in August 2001. Prosecutors are arguing that Moussaoui should be executed because he lied to and misled the FBI.

Mr. Novak said prosecutors had discovered the error late Friday and begun an immediate investigation.

With the jury out of the courtroom, Judge Brinkema then recessed the trial in order to decide what to do. “This is the second significant mistake by the government affecting the constitutional rights of this defendant and …impacting the criminal justice system in this country,” she said. “In the context of a death case, I have to think about this issue.”

Judge Brinkema was referring to a rebuke she gave the government on Thursday after prosecutors questioned why Moussaoui had not contacted the FBI to offer information after he was jailed in Minnesota in August 2001. At the time, Moussaoui had stopped speaking with agents and had asked for an attorney, and defense lawyers said the prosecution’s question violated Moussaoui’s constitutional rights against incriminating itself.

The judge has already thrown out the death penalty in the case once, in 2003, after the government disobeyed her order to allow Moussaoui’s lawyers to interview captured Al Qaeda leaders who they said could clear him. After several years of delays, she was overruled by a higher court.