Ranuccio I Farnese reigned as Duke of Parma, Piacenza and Castro from 1592. A firm believer in absolute monarchy, Ranuccio, in 1594, centralised the administration of Parma and Piacenza, thus rescinding the nobles' hitherto vast prerogative. He is best remembered for the "Great Justice" of 1612, which saw the executions of a large number of Piacentine nobles suspected of plotting against him. Claudia Colla his mistress and her mother were accused of using witchcraft to stop him from having offsprings, and both were sentenced to death by burning. Because one of the conspirators, Gianfrancesco Sanvitale, falsely implicated several Italian princes, namely Vincenzo Gonzaga, Duke of Mantua and Cesare d'Este, Duke of Modena, in the plot, Vincenzo and Cesare's names appeared on the list of conspirators during formal court proceedings; as a result, Ranuccio's reputation among the rulers of Italy was irreparably damaged because it was evident that he gave credence to Gianfrancesco's obviously false confession.