Two Muslims stood trial on Wednesday accused of running internet sites calling for holy war and supporting a criminal organisation.
It is the second trial in the Swiss Federal Court about possible terrorist involvement since the September 11 attacks in the United States. But an expert says securing a conviction may be problematic.
The accused, a couple that lived near Fribourg in western Switzerland, allegedly ran four websites as well as online forums. They were arrested in February 2005.
Prosecutors have said the sites were set up to promote racially motivated crimes. They were also allegedly used to publicise claims of responsibility for attacks and threats against Western countries.
A 39-year-old Tunisian national is charged with setting up the internet sites. His 48-year-old Belgian wife is accused of aiding and abetting him, as well as running her own website. They are both accused of inciting violence.
Both defendants maintained their innocence and pleaded not guilty on the first day of the trial.
The content on the websites and other data seized by the federal police left little to the imagination. Pictures and videos are said to have shown the execution of an Egyptian driver, the massacre of bus passengers in Iraq, the decapitation of a Korean hostage and the murder of an American.
According to Gilles Monnier, a professor of criminal law at Lausanne University, the difficulty of securing a conviction in this case is to prove how much the accused knew what was going on.
"If a person who manages a forum filters the comments on a regular basis, it is hard to claim that they didn't know what was going on," he told swissinfo. "On the other hand, if there is no surveillance, you can also say there is no responsibility."
Both accused - who were held by Swiss police for less than one month during the investigation - have denied knowing everything that was happening on the sites. While admitting that they are Islamists and saying that they want to resist oppression, they claim to be against the loss of innocent lives.
The man is alleged to have used the forums to suggest that two French journalists taken hostage in Iraq be exchanged for a ransom, killed or set free.
The woman for her part allegedly told another correspondent to go "fight the war in Iraq".
The husband is now based in Lausanne. His wife, who returned to Belgium after being expelled, received a promise of safe-conduct to attend the trial at the Federal Criminal Court in Bellinzona.
This case is the second this year focusing on Islamic terrorism, with prosecutors hoping to secure convictions this time round.
In February they suffered a setback when seven defendants were cleared of belonging to and supporting al-Qaeda.
"This is a criminal case, so the prosecution has to prove intent," said Monnier. "Showing that the accused were negligent will not be enough."
The Belgian woman is the widow of a suicide bomber who killed anti-Taliban warlord Ahmed Shah Massoud in 2001.
In an interview with CNN last year she admitted to being devoted to al-Qaeda leader Osama bin Laden.
The woman was cleared in 2003 by a Belgian court of charges of complicity in Massoud's murder.
swissinfo, Scott Capper
Two other cases of suspected Islamic terrorism are pending.
A Saudi Arabian businessman, Y.K., is alleged to have transferred millions from his Swiss bank account to people belonging to al-Qaeda. The case has been with the investigating judge since June 2005.
A preliminary inquiry was opened last September into several people of North Africa origin, arrested in Switzerland and accused of theft in connection with a planned terrorist attack on an Israeli aircraft.
The case of the Egyptian businessman, Youssef Nada, and his al-Taqwa bank was dropped due to a lack of evidence. He was suspected of supporting terrorism. Nada is still on the UN list of terrorist suspects and is under house arrest in Campione d'Italia.
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