[4] In 875, shortly after Charles the Bald's imperial coronation, Formosus fled Rome in fear of then-pope John VIII.

A few months later in 876, at a synod in Santa Maria Rotunda, John VIII issued a series of accusations against Formosus and some of his associates.

He asserted that Formosus had corrupted the mind of the Bulgarians "so that, so long as [Formosus] was alive, [they] would not accept any other bishop from the apostolic see,"[8] that he and his fellow conspirators had attempted to usurp the papacy from John, and finally that he had deserted his see in Porto and was conspiring "against the salvation of the state[verification needed] and of our beloved Charles [the Bald].

According to Auxilius, Formosus begged the bishops for their forgiveness, and in return for removal of the excommunication, swore an oath to remain a layman for the rest of his life, to never again enter Rome, and to make no attempts to resume his former see at Porto.

Two further accusations were also made against Formosus at the Cadaver Synod: that he had committed perjury and that he had attempted to exercise the office of bishop as a layman.

[16] In 893 Formosus, apparently nervous about Guy's aggression, invited the Carolingian Arnulf of Carinthia to invade Italy and receive the imperial crown.

Lambert and his mother, the empress Angiltrude, entered Rome around the time that Stephen VI became pope, and the Cadaver Synod was conducted directly afterwards, at the beginning of 897.

[citation needed] The dominant interpretation of these events until the early twentieth century was straightforward: Formosus had always been a pro-Carolingian, and his crowning of Lambert in 892 was coerced.

After the death of Arnulf and the collapse of Carolingian authority in Rome, Lambert entered the city and forced Stephen to convene the Cadaver Synod, both to re-assert his claim to the imperial crown and perhaps also to exact posthumous revenge upon Formosus.

"[18] This position has been accepted by another scholar: Girolamo Arnaldi argued that Formosus did not pursue an exclusively pro-Carolingian policy, and that he even had friendly relations with Lambert as late as 895.

[19] Arnaldi argues that it was Guy IV, who had entered Rome along with Lambert and his mother Angiltrude in January 897, who provided the impetus for the synod.

[20] Probably around January 897, Stephen VI ordered that the corpse of his predecessor Formosus be removed from its tomb and brought to the papal court for judgment.