He is the only person ever to be tried specifically for playing a part in the 9/11 terrorist attacks on the United States. Considerable doubts have since been raised about the role that he played in the conspiracy - if any.
In May 2006, Zacarias Moussaoui was sentenced to life imprisonment, without possibility of parole, in solitary confinement at the "Alcatraz of the Rockies" - the maximum jail in Florence, Colorado. His mother has not spoken to him, or received a reply to one of her letters, for nearly six years. The American authorities say he refuses to speak to her. She believes total isolation has been imposed as part of his punishment.
Wafi is convinced Moussaoui had nothing to do with the attacks on the Pentagon and the Twin Towers. She says he is being "punished for what he said (at his trial) ... not for what he did. He was an ideal scapegoat."
She admits that her son, while studying for a master's degree in London between 1993 and 1995, became an Islamist and an extremist without her realising it. She blames, among other things, the break-up of her marriage with his abusive father when he was 4 years old. She also blames two "wounding" incidents in his French adolescence.
The first was when his school careers adviser pushed him, although he was always an excellent student, towards minor, technical studies. "The clear implication was that he was only an Arab and would need nothing more," she said. The second "psychological wound" was when the father of his teenage sweetheart warned him off, again because he was an Arab. In the last 10 years, Wafi, 65, has publicly defended her son while campaigning against extremist forms of Islam.
She has befriended five families of 9/11 victims in the US. She has joined the French feminist group, Ni Putes, Ni Soumises (neither whores, nor submissive), which tries to persuade French women of Arab and African origin to resist male oppression.
She visits schools to lecture girls of North African origin on the evils of arranged marriages.
At the age of 14, Aicha Wafi was married in Morocco to a man she did not know.
"I love my son more than ever," she said, kissing one of his photographs. "Some people find that strange, but to me it is not strange. It was easy to love the little boy that ran around here, full of life.
"Who is going to love Zacarias now, in his cell underground in America, unless it is his mother?"
Wafi said she was sickened by the slaughter of 9/11 - and remains so.
"I lost my first daughter when she was four months old. I know what it means for a parent to lose a child. That is why I reached out to the families of the people who died."
She angrily dismisses radical and extremist forms of Islam as a "perversion", an "obsession with power", and "nothing to do with the real Islam, which is about love and respect and tolerance".
She is convinced, however, that radical Islam was only partly responsible for what happened on September 11, 2001.
"It was also Bush," she said. "I believe that the Bush administration willed it to happen, even if they were not directly involved. I believe that Osama bin Laden always worked closely with the Americans - I mean the American Government, not the American people. It was all about power and money. Bush wanted the excuse to attack Iraq."
Wafi is warm and articulate but remains, after 10 years, an angry woman. She is angry with France, believing it taught her son to be French, and then told him that he was not good enough to be French.
She is angry with Britain for giving free rein to radical preachers in London who converted her son to a "poisonous, perverted" form of Islam. She is angry with her other son, Abd Samad Moussaoui who, she believes, helped the French security services in their post 9/11 investigations of Zacarias.
Bizarrely, perhaps, she cannot bring herself to be angry with Zacarias himself. He was arrested in the US the month before 9/11 on relatively minor immigration charges. He was in custody in Minnesota at the time of the attacks. He had taken part in flight training and flight simulation programmes in the US (and failed).
According to one version of events, he was a "reserve" member of the 9/l1 team. According to one of his own conflicting accounts, which he has since withdrawn, he was due to take part in a follow-up attack with shoe-bomber Richard Reid. He was convicted of conspiracy to commit acts of terrorism, conspiracy to commit aircraft piracy and conspiracy to destroy aircraft. "I am convinced he was nothing to do with 9/11," Wafi said.
"Some of the things that he said at the trial - against Americans, against Jews - were abominable, unacceptable. But can you be given life imprisonment for that? OK he went in for pilot training. But many people do that. It proves nothing. At the very most, you can say that he may have wanted to be a terrorist, but there is no shred of evidence that he helped to plan 9/l1."
- Independent