Answer
Pope Stephen VI was the pope who officiated the Cadaver Synod. The Cadaver Synod was a church trial held in 897 to depose the dead Pope Formosus. The trial was presided over by Pope Stephen VI, who had Formosus' body exhumed and put on trial. Formosus was found guilty and his body was mutilated. The Cadaver Synod was a controversial event that led to Stephen VI's own deposition and death.