Khalid Sheikh Mohammed and two other men went on trial for plotting the suicide bombing of a historic synagogue on the Tunisian island of Djerba.
Mohammed is accused of having commanded and financed the Tunisia attack. He is being tried in France in absentia because he is being held by the U.S. government at Guantanamo Bay, Cuba. Mohammed is the suspected mastermind of the 2001 terror attacks on New York and Washington.
But the two other men were present in the Paris courtroom on Monday -- German national Christian Ganczarski and Tunisian Walid Nawar, who is the brother of the Tunisian suicide bomber. Nawar is accused of helping his brother carry out the 2002 synagogue bombing that killed 21 people.
Ganczarski's lawyer, Sebastien Bono, denied his client was a terrorist.
Bono told French radio that Ganczarski was a convert to Islam who had studied in Saudi Arabia. He said his client later lived in Afghanistan with his family, but that Ganczarski was interested in the import-export business there, not radical Islam.
The three men are being tried in France for complicity in attempted murder in relation to the Tunisia terrorist operation. If found guilty, they could face life in prison. The trial is scheduled to end next month.