Many European citizens left the continent to join the Islamic State group. As the war against IS winds down, hundreds of them are still imprisoned in Kurdish-controlled regions of northern Syria. United States President Donald Trump has demanded European countries take back their citizens being held by the Kurds. Many of the returnees would likely end up in prison in Europe. Some politicians and experts worry that in Germany, authorities would then be confronted with the challenge of preventing Islamic extremists from turning the country's prisons into breeding grounds for radicalization. According to Michael Kiefer, an expert on Salafism and radicalization prevention who teaches at the University of Osnabrück, that is a very real danger.

DW: If you look at Islamic terrorism in Europe in recent years, are prisons potentially places where Muslim inmates are radicalized?

Michael Kiefer: Taking into account the experience we've had in Western Europe, yes. Look at the men who killed 130 people in Paris on November 13, 2015 — they were imprisoned repeatedly, they more or less got acquainted with jihadism in prison. There, they used religion to prove they were up for violence and delinquency, and then they began their march. In that respect, prisons are highly problematic institutions.

The Islamic State group is more or less destroyed. We expect several hundred people to return to Germany from territory previously controlled by the terrorist militia, and many of them will likely end up in prison. Can these people foment Salafist or jihadi radicalization in prison?

They certainly can. We must assume that quite a few crafty senior figures will return and that their resolve is unwavering. We can expect them to continue to agitate in prison. In fact, they will see this as an excellent breeding ground and of course they will try to approach their fellow prisoners accordingly. The judicial authorities are well advised not to offer them a platform to agitate in the first place.

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Many inmates in German prisons are Muslim. In the state of North Rhine-Westphalia, for instance, almost one out of four inmates is Muslim. Have German prisons made arrangements to counter radicalization?

I doubt it. There is a lack of well-trained specialists, including social workers who are familiar with these phenomena and who could work with the prisoners accordingly. The prisons simply don't have them, these people actually still need to be trained. North Rhine-Westphalia has at least recognized the problem. The state's Justice Ministry has launched a program, but I can't say how successful it is.

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How important are prison imams in that respect? We know that many people who became radical Salafists in prison were by no means fervent Muslims before changing their views. Could prison imams give Muslim inmates solid arguments to counter jihadi ideology?

That's quite possible. Well thought-through spiritual guidance in prisons can always be part of proper psychosocial support. We must assume that prison inmates are already experiencing major crises, so assistance and support can indeed have an immunizing effect. We must ask ourselves why people who radicalize others are successful in prison — it's because they have something to offer the young inmates that the prison does not. They encourage them, support them, pat them on the back and tell them they've made the right choice. Supporting people in their daily lives is one thing, but they offer a complete identity model, they advise rethinking role models while offering comradeship and support, even beyond the time served in prison. That should not be underestimated.