Fifteen years? That's it?! In fifteen years, he will be only 47 and still eager, willing, and able to serve as a party to more terrorist attacks.
Believe it or not, that's a pretty tough sentence for a German Court. I was involved with the SFC Clyde Conrad spy case in the 80's. Conrad was tried in a German Court. He was convicted and received a life sentence. However, under German law, life only means 18 years. In his case, he died after three years in prison, so life was life.