Germany's highest court today overturned the verdict against the only person convicted of involvement in the Sept. 11 terror attacks and ordered a retrial.The man, Mounir el-Motassadeq, was sentenced to 15 years in prison in February 2003 after being found guilty of 3,066 counts of accessory to murder and of playing a crucial logistical role for the members of the Qaeda cell in Hamburg that produced three of the Sept. 11 pilots.