Mohammed Bouyeri, the Dutch Moroccan who savagely slaughtered Dutch filmmaker Theo van Gogh on November 2, 2004, has already been convicted and sentenced to life imprisonment. Now a new trial underway in Amsterdam aims to determine whether Bouyeri acted alone. There is ample reason to doubt that he did. Specifically, the prosecution seeks to determine the extent of Bouyeri’s involvement with a group of radical Muslims known as “The Hofstadgroup.” The question before them: Did Bouyeri act on his own, or did he conspire with other members of the Hofstadgroup to murder van Gogh? Rumors abound, but there is no...