Human rights groups, the Office of the Chief Mufti and various historians, political scientists and critics of the GERB government counter that the trial, at this moment taking place in the Pazardzhik court, is nothing but an attempt to justify a botched act of brutality against innocent Bulgarian citizens who happen to be Muslim. It is designed to create the impression, both domestically and internationally, that the DANS is doing something meaningful to counter anti-constitutional activities and prevent terrorism.
At the time of the 2010 arrests, local witnesses reported bizarre scenes of hooded policemen ransacking homes and impounding books in Arabic they couldn't even read the titles of. One family whose home was raided in this way quickly alerted neighbours and asked them to come over and make a list of all material being confiscated by the police, for fear of possible forgery and manipulation. Reportedly, the police had no proper search warrants.
A commentator asked ironically, "In a country where Hitler's Mein Kempf is freely available in translation, the police arrest people for possession of books in languages they do not understand. Well, I have some very dangerous books in Russian at my home. Will they come and arrest me?"
The 13 are being tried under a clause in the Penal Code that dates back to the time of Communism and that was last used during the late 1980s, when the forcible Bulgarianisation of Turks, euphemistically known as the Revival Process, was taking place.
One defendant from Madan allegedly set up a teenage football club to "propagate radical Islam."
Krasimir Kanev, the chairman of the Bulgarian Helsinki Committee, has said that the defendants are being charged with "fundamentalism" without any proof. There is no evidence of any coercion or violence, Kanev has said, adding that telling people not to participate in elections, which the defendants allegedly did, is not a crime.
Telling people that God is above the state is not a crime either, Kanev has said. Otherwise, the Pope should have been put in jail a long time ago.
Bulgaria is the home of about a million Muslims, both Turks and ethnic Bulgarians who profess Islam. It is the EU member state with the largest percentage of non-immigrant Muslims.
Ever since Bulgaria gained independence in 1878, its Muslims have been subject to various pressures and sometimes violence, culminating in the mid-1980s, when the country's Turks were forcibly given new, Bulgarian names. Turkish was banned, mosques were closed or destroyed, and the persistent campaign of forcible Bulgarianisation led to the 1989 exodus of about 350,000 Turks, the largest migration of people in post-war Europe and a precursor to the ethnic cleansing in the former Yugoslavia.
According to Dr Antonina Zhelyazkova, the head of the International Centre for Minority Studies in Sofia, the general public is put off by the language being used by the media and the politicians. The defendants never made a claim they were not proponents of Salafism. "Salafism" is unknown in Bulgaria and mentioning it caused a stir.
Dr Zhelyazkova sees a recurrent pattern of state-sponsored intimidation of Bulgaria's Muslims, which she says is particularly dangerous against the background of present-day attitudes worldwide and the 18 July 2012 terrorist attack in Burgas, which remains unsolved.
One possible reason for the trial to be held at all may be the government's attempt to harass the defendants not to press criminal charges against the DANS for illegally entering their homes and confiscating their property.
Human rights groups say that whatever the outcome, the case is likely to end up at the International Human Rights Court in Strasbourg, where, they surmise, Bulgaria will be made to pay huge indemnities – with taxpayers' money.