The federal government is hoping a jury will come to the same conclusion about Zacarias Moussaoui as the commission that investigated the Sept 11, 2001, attacks: that the al Qaeda operative was likely being groomed as one of the hijackers.

Prosecutors have long contended that Moussaoui, the only person charged in an American courtroom in connection with the terrorist attacks, was involved in a broad al Qaeda plot that led to the hijackings. But to secure a death sentence, they need to directly link Moussaoui to the events of that day.

In its report issued Thursday, the commission, drawing on much of the same material and evidence as prosecutors, said that Moussaoui was personally selected by Osama bin Laden and that he was being "primed as a possible pilot" for Sept. 11. Moussaoui was arrested a month earlier and couldn't go forward.

Moussaoui's attorneys criticized the report yesterday, saying the commission had imperiled Moussaoui's right to a fair trial by asserting so publicly that he is guilty. They expressed concern that the massive publicity will affect potential jurors.

"It's virtually unprecedented for any kind of commission to release a report containing conclusions that will affect an ongoing capital case," said attorney Edward B. MacMahon Jr. "We always thought it would be almost impossible to have a fair trial in this case. This certainly isn't going to make that task any easier."

The commission's spokesman did not return calls yesterday. Federal prosecutors in Alexandria declined to comment, but the Justice Department has said repeatedly that Moussaoui would get a fair trial.

Moussaoui was indicted in December 2001, but the case has been tied up in the courts over Moussaoui's requests for access to top al Qaeda detainees he argues can aid his defense.

One of those detainees is former al Qaeda operations chief Khalid Sheik Mohammed, the mastermind of the Sept. 11 plot. The commission report, relying on interrogation summaries provided by the government, said that Mohammed "denies ever considering" Moussaoui for the Sept. 11 hijackings and that Moussaoui was instead aiming for the second wave.

But Mohammad acknowledged that planning for the second wave had stalled. That, combined with Mohammad's instructions to another operative to send Moussaoui $14,000 in July 2001 in case another hijacker might drop out, led the commission to a different conclusion.

"We therefore believe," the report said, "that the effort to push Zacarias Moussaoui forward in August 2001 lends credence to the suspicion that he was being primed as a possible pilot" on Sept. 11.

The report said Mohammad considered Moussaoui unreliable but did not remove him from the operation because Moussaoui had been "selected and assigned by bin Laden himself." It said Moussaoui had purchased two knives and taken other actions "that closely resembled those of the 9/11 hijackers" -- language similar to that in Moussaoui's indictment.

And in a footnote, the commission cast doubt on statements made by another top al Qaeda detainee who has been sought by Moussaoui's defense team: Ramzi Binalshibh. "Binalshibh has sought, somewhat incredibly, to exculpate a host of individuals, including Moussaoui, from complicity in the 9/11 plot," the footnote said.

The report cannot be admitted into evidence by the prosecution because it is considered hearsay, experts said. But prosecutors are likely to follow similar arguments in trying to secure a death sentence for Moussaoui. Moussaoui could receive life in prison if convicted on the broad conspiracy charges against him. But under federal rules of evidence, a death sentence would require that prosecutors link him more directly to the deaths on Sept. 11. That task has always been complicated by the fact that Moussaoui was sitting in a jail cell on immigration charges when the planes hit the World Trade Center and Pentagon.

Legal experts split over whether the commission's conclusions will affect the case by prejudicing potential jurors.

"It's a serious due process problem when a government commission issues a report indicating that an individual currently on trial for his life is probably guilty," said Kate Martin, director of the Center for National Security Studies, a Washington civil liberties group.

"This report is on the front page of every newspaper and is dominating TV news," she said. "For people reading it, it sounds like an official government conclusion about Moussaoui."

Kim Lane Scheppele, a law professor at the University of Pennsylvania, said she understands why the defense is upset.

"They should be screaming about this," said Scheppele, who teaches a course on terrorism and evidence. "But I suspect they'll be able to find 12 jurors who have never heard of it."

Zacarias Moussaoui was arrested a month before the 2001 attacks.Edward B. MacMahon Jr. said it will be harder to ensure a fair trial.