High Quality Content by WIKIPEDIA articles! Zacarias Moussaoui is a French citizen who was convicted of conspiring to kill citizens of the USA as part of the September 11, 2001, terrorist attacks. As a result of his conviction, he is serving a life sentence without parole at the Federal ADX Supermax prison in Florence, Colorado. Moussaoui was alleged to have been a replacement for the "first" 20th hijacker, possibly Ramzi Binalshibh. Binalshibh and Zakariyah Essabar were denied visas. However, prosecutors in Moussaoui's drawn-out trial had difficulty directly connecting him to the 19 participants.