 FACT: Mulder refers to a crucifix hanging in what is usually  considered an inverted position as being a "protest, a sacrilege  against the Church". In Roman Catholic symbology, an "inverted"  cross is known as the Cross of Saint Peter. Later in the episode,  Scully gives the correct interpretation referring to a legend that  when Peter was martyred, he asked to be crucified head down because  he was unworthy to die in the same manner as Christ.