Pope Adrian I, who had constantly lent Charlemagne his strong support, died on Christmas day, 795. He was succeeded by Leo III. Leo was a popular figure from a plebeian family, and as such he was despised by the Roman aristocracy, who remained faithful to the high-born family of Adrian. The result was an effort to depose him.
On April 25, 799, Leo was leading a procession towards the Church of San Silvestro when he was set upon by armed men. More dead than alive, he was rescued by the duke of Spoleto, one of Charlemagne’s ministers, and taken to the monastery of Saint Erasmus.
While he was in confinement recovering from his wounds, Pope Leo expected Charlemagne to speak out at once in his defense. The matter was not a simple one, however. Charges had been brought against the new pope which would have to be investigated. In addition, Charlemagne had kept his close ties with the family of the deceased Adrian. Whichever faction he supported in the crisis would take control of the Papal States and affect his relations with Italy for a long time to come.
Charlemagne remained silent on the matter and invited the pope to visit him at Paderborn when he was well enough to travel. By the time Leo arrived in Paderborn, however, Charlemagne seems to have made up his mind. The pope was welcomed with highest honors. When he returned to Rome, an inquest was held to examine the charges levied against him (they included simony, adultery and perjury), but the proceedings, carried out by bishops and counts close to Charlemagne, seemed to condemn the accusers rather than the accused. The findings were returned to Charlemagne’s court, where the king himself was to read them and take action.
Charlemagne issued no decree, but in the autumn of 800 left for Rome. The final act in the exoneration of Pope Leo took place during the ensuing ceremony in Saint Peter’s Basilica. Leo swore to his innocence before the highest pontifical authorities, an amalgam of Roman aristocrats and Frankish nobility, and Charlemagne formally absolved him of all charges.