Zacarias Moussaoui - delusional paranoid schizophrenic, or cold calculating killer?
By Jonathan Beale
BBC News, Washington
As he himself shouted out in court: "Crazy or not crazy? That is the question."
Moussaoui was spared the death penalty
His links with terror, though, were never in doubt. He had trained in Afghanistan with al-Qaeda.
He had met and sworn allegiance to Osama Bin Laden.
He arrived in America in 2001. He went to Minnesota to learn how to fly.
"He was a little more cantankerous than some of the other students, I would say. He was a little more pushy, a little more bossy," Brenda Keene
of Airman Flight School says.
The FBI grew suspicious and he was arrested in August.
Rejoicing amid terror
One month later the Twin Towers were attacked.
The government argued that Moussaoui had always known about the 9/11 plot.
He told the court that in his cell he rejoiced as the World Trade Center burned and collapsed.
The prosecution played the jury tapes of the victims' desperate last minutes.
"There's no one here yet and the floor is completely engulfed. We're on the floor and we can't breathe. And it's very, very, very hot. I'm going to die, aren't I?" Melissa Doi frantically asked an emergency dispatcher from the 83rd floor of the south tower.
"No, no, no, no," the dispatcher replied.
"I'm going to die, aren't I?" the woman repeated.
The dispatcher's answer was a simple: "Ma'am, say your prayers."
And for some there was a sense of justice when the first part of the trial concluded at the beginning of April. The jury unanimously agreed that Moussaoui was eligible for execution.
"Yes, I am glad that this part is over," Rosemary Dillard told reporters outside the court.
"But it's not just for my husband. It's about what he did to the United States. He did that to all of you."
It was Moussaoui's own evidence that transformed this case.
He stunned the court and his lawyers when he claimed in late March he was to have been part of the 9/11 attacks.
He said he was planning to fly a fifth plane into the White House - contradicting earlier statements denying his involvement.
Moussaoui said Richard Reid was to have seized a plane with him
Moussaoui's own erratic outbursts in court were accompanied by disputable claims.
He said that Richard Reid, the British shoe bomber, was to act as his accomplice in hijacking a fifth plane - but there is no evidence of that.
Reid wasn't even in the US at the time.
Was Moussaoui now deliberately seeking martyrdom?
His defence team raised questions about his sanity.
They detailed his troubled upbringing as an immigrant in France.
His two sisters described their own mental illness and how they had suffered at the hands of an abusive father.
Moussaoui's sister said his father had abused him
Zacarias, they said, had also suffered abuse from the man.
"He almost killed us all, what, all four of us, I think. He was a man who should never have had children, you know," Djamilla Moussaoui said.
"I also suffer from psychosis, with schizophrenic tendencies as my shrink would say," Nadia Moussaoui said.
"I too suffer from terrible anxiety, the inability to connect socially, to form a normal social life ... difficulty working, truly difficult. There you have it."
In the end, Moussaoui was never able to carry out a terrorist attack.
He used his platform in court to seek martyrdom instead.
Even after the jury's verdict of life in prison, though, the question still lingers - is this the man who could have prevented 9/11?