Merah told police that he was a member of the Al Qaida terror network but he operated almost alone, allegedly working with his older brother Abdelkader.
"We are facing a new type of radicalisation, what might be called the model of the lone wolf: individuals who are influenced by some networks, but not directly involved in them, who act in a solitary manner,” Khosrokhavar told RFI.
French intelligence had been tracking Merah for some years, after his return from fighting alongside the Taliban in Afghanistan and Pakistan. But, Khosrokhavar argues, the lone wolves’ relative isolation makes it difficult to know when they are planning attacks or to detain them beforehand.
Al Qaeda and other armed Islamist groups have received a series of setbacks in the last couple of years. The movement’s leader Osama bin Laden was killed by US troops in Pakistan last year and drone attacks, other targeted operations have eliminated a number of Taliban commanders in Afghanistan and the world’s spies have gained experience in tracking them.
But that has had some unforeseen results.
In Afghanistan a new generation of commanders is said to be more uncompromising and less open to negotiations than their predecessors.
And in the rest of the world it is less easy to keep tabs on individuals working alone or in very small groups.
"In a way lone wolves are the outcome of the intelligence and security services’ successes,” Khosrokhavar says. “It’s because they cannot build up networks that they act in a solitary manner.”
So what sort of person takes to terror?
"There is no single profile,” Khosrokhavar explains. “But one can say there are two or three
“One is the young man who feels he is not integrated, he is not recognised as a French citizen. He is excluded economically, socially, culturally and so on.”
But not all jihadists come from immigrant families. Some have converted to Islam.
"We are in a society where people feel that major ideologies are cool, and they need some kind of radicalisation,” comments Khosrokhavar. “Before that in the 1970s you had the far left. But the far left has died down in Europe. You don’t have any kind of alternative. You have the far right, you have radical Islam. And I think for the time being these two radical ideologies give birth to major types of violence.”
Some politicians make the problem worse by harping on it, he argues, but that probably is not the main reason for individuals turning to violence.
"It’s a civil society measure. People should become conscious, so that they tell the authorities about people they worry might become violent. Sometimes it’s the lesser evil. The government cannot do so much in these cases, because in a democracy you cannot put in jail somebody merely because he has radical ideas. So it’s a question that cannot be easily solved."