The Hamburg cell played a key role in the 9/11 attacks
The retrial of Mounir al-Motassadek examined his links to the Hamburg-based "cell" at the heart of the 11 September 2001 attacks.
He was arrested in Hamburg 11 weeks after the attacks on New York and Washington. He admitted having been close to the 9/11 hijackers but denied any knowledge of the plot.
Judges at his retrial found him guilty of membership of a terror group, but cleared him of being an accessory to the 9/11 murders.
German prosecutors said the Hamburg cell consisted of eight members: three suicide pilots, three logistical planners and two others whose role remains vague, but who might also have become suicide pilots.
The cell was active and embarking on the plot to attack US targets by the summer of 1999, the prosecutors said.
Mohammed Atta, a wealthy Egyptian, is believed to have been a key figure in the Hamburg cell, but also the ringleader of all 19 of the 9/11 hijackers.
In 1996, Motassadek signed Atta's will along with Abdelghani Mzoudi, a fellow Moroccan who was acquitted by the same Hamburg court in February.
Mr Mzoudi shared a Marien Street apartment in Hamburg with Atta and suspected top al-Qaeda operative Ramzi Binalshibh, who is in US custody. Mr Binalshibh claimed in a television interview to have been a mastermind behind the 9/11 plot.
Along with Atta, the Hamburg-based suicide pilots were identified as Marwan al-Shehhi and Ziad Jarrah.
Motassadek operated a bank account under Shehhi's name - allegedly used to fund flight lessons in America and provide the expenses for American visa applications for the group.
Shehhi, from the United Arab Emirates, and Jarrah, from Lebanon, also lived in the Marien Street flat at various times.
Atta, Shehhi, Jarrah and Mzoudi were all enrolled on science courses in Hamburg in the 1990s.
Germany's second largest city is home to about 200,000 Muslims, and the radicals blend in easily with the ordinary Muslim population.
Ramzi Binalshibh: Arrested in Karachi in September 2002
Police say even now they do not have the resources to track all of the militants.
Investigators believe that al-Qaeda has operated in the city since at least 1999.
According to Germany's chief prosecutor, Kay Nehm, the hijackers and their accomplices became acquainted at a mosque frequented by vehemently anti-Western Muslims.
"All of the members of this cell shared the same religious convictions, an Islamic lifestyle, a feeling of being out of place in unfamiliar cultural surroundings that they weren't used to," Mr Nehm said.
"At the centre of this stood a hatred of world Jewry and the United States."
He added that by October 1999 at the latest, the group began talking about "a holy war against the United States in which the maximum number of people could be killed".
Money in an account set up by Atta in Florida was traced back to Hamburg.
Investigators say the Hamburg group included two other students still on the run - Said Bahaji and Zakariya Essabar.
They are thought to have left Germany shortly before 11 September 2001.
Mr Binalshibh is thought to have been the cell's most senior contact to Osama Bin Laden's al-Qaeda network.
He is believed to have been planning to join the hijackers in the US and train as a pilot, but was refused a visa four times.