By Matthew Davis
BBC News, Washington
A US courtroom near the site of a 9/11 terror strike is wrestling with the question of how to find a neutral jury to hear the death penalty trial of a man once described as the "20th hijacker".
Moussaoui denies knowledge of the 11 September attacks
In the four years since the terror attacks, Zacarias Moussaoui has become the public face of terrorism.
He is the only person convicted in the US in connection with the 2001 strikes, and admits plotting with al-Qaeda to attack buildings there.
His sentencing trial is taking place just a few miles from the Pentagon, where a hijacked aircraft was crashed on 11 September 2001, killing 184 people.
It is from this area - densely populated with military and government workers - that the jurors will be drawn.
Trial judge Leonie Brinkema is going to great lengths to find a group of Americans - 12 jurors and six alternates - who can set aside what they know, or think they know, about the case.
The main tool in this search is a 50-page, 159-question paper which probes jurors' backgrounds, as well as their religious beliefs, feelings about Arabs and Muslims and their reaction to the 9/11 attacks.
The depth and range of the questions speaks to the huge impact that the terror strikes have had on the lives of Americans. They include:
- Whether jurors read, speak or understand Arabic, watch Arabic television or read Arabic newspapers, or have contact with Muslims
- If, since 9/11, any of their family members or close friends have been killed in combat in Iraq, Afghanistan or elsewhere in the Middle East
- What opinions they hold about the performance of the FBI at Waco, after 9/11 and on other controversial investigations
- Whether they were in Washington or New York on 9/11, and what impact the attacks had on their lives
Paul Butler, a former federal prosecutor and now a law professor at George Washington University, says the greatest concern will be to weed out people who want to be on the jury of a notorious case.
He told the BBC: "This is not just a death penalty case, it is a high profile case that involves one of the worst crimes ever committed on US soil. That is why it will take a month to find a jury."
Some 500 prospective jurors have been called to fill in questionnaires. This pool will be whittled down and groups of 12 jurors questioned in court.
The aim is to have a pool of 85 qualified jurors from which the final selection can be made.
Prof Butler believes the "careful process" will take time, but says the court should have no trouble finding enough candidates.
"There has been so much aftermath of 9/11, this is just one small - and complicated - part," he said.
"Moussaoui has a lot going for him, in the sense that when the 9/11 attacks took place he can say he was locked up in a Virginia jail.
"If he had been in the plane that hit the Pentagon and somehow miraculously survived, then that's when I think you would have trouble finding a neutral jury."
Moussaoui has pleaded guilty to six charges linking him to al-Qaeda's plans to attack the US, and the jury will have to decide if he should face life in prison or the death penalty.
The self-confessed al-Qaeda plotter has described the proceedings as a "circus", and refuses to recognise the legitimacy of the court.
On Monday he was expelled from court after refusing to remain silent.
Moussaoui was arrested at a flight school in Minnesota, a month before the 9/11 attacks.
He has admitted that he was planning to fly a plane into the White House, but insists he knew nothing of the wider 11 September plot.
The proceedings against him will be closely watched by many of the relatives of the almost 3,000 people killed on 9/11.
Many will be looking for justice, and some for vengeance for the deaths of their loved ones.
Over the next month, Judge Brinkema will try to ensure that those judging Moussaoui will be looking only for the former.