De-radicalization programs in Germany are failing, an investigation by a German radio station has discovered, since fighters return to extremism after returning to Germany, as reported by Breitbart and The Express.

One fighter in particular was enrolled in a de-radicalization program when he returned from Syria in 2014. Despite boasting he had killed people and posting pictures of himself posing with weapons online, there had not been enough evidence to convict him of a specific terrorism offence and send him to prison.

After going through the program he went on to make a video claiming "all over the world Muslims are oppressed" and warning authorities that even if they "throw us in prison, our thoughts will still be on the run."

He "is respected by peers from the jihadist milieu of returned Mujahid — so-called holy warriors" according to German radio station Der Funkstreizug, which investigated the government's de-radicalization program.

The station added that "he makes [Islamic extremist] YouTube videos. He obviously produces his own videos and [spreads his ideology] by means of music, pictures and writing his messages."

The research found that most Salafis do not want to be deradicalized and because the deradicalization programs rely on cooperation they have limited impact.

Earlier this year German TV station N-TV interviewed a former Islamic State fighter who had returned to Germany. He said, "Most returnees that we know return to the Salafist scene. In my opinion, this is not a sign that they are a particular risk. These are their friends … they are treated as heroes."

Salafists follow the austere ultraconservative brand of Sunni Islam practiced by Saudi Arabia and by jihadists.

He argued that placing returnees in prison could be dangerous since they would be "hailed as war heroes and seen as political prisoners" and therefore could radicalize other inmates.

This is despite also saying that "many of them are likely to mellow or become disappointed. They no longer hold much of the Islamic State ideology and have returned to distance themselves from it."

According to the investigation so far, the German government has spent $440,440 on the de-radicalization program.