Plutarch, Life of Dion
34-35 (tr. Bernadotte Perrin):
Now, there was a certain Sosis, a man whose baseness and impudence gave him renown in Syracuse, where it was thought that abundance of liberty could only be shown by such license of speech as his. This man, with hostile designs upon Dion, first rose in an assembly and roundly abused the Syracusans for not comprehending that they had merely exchanged a stupid and drunken tyrant for a watchful and sober master; and having thus declared himself an open enemy of Dion, he left the assembly. Next, on the following day he was seen running through the city naked, his head and face covered with blood, as though he were trying to escape pursuit. In this condition he dashed into the assembly and told the people there that he had been set upon by Dion's mercenaries, and showed them his head with its wounds. He found many to share his resentment and take sides with him against Dion, who, they said, was committing dire acts of tyranny, if by murder and peril of life he sought to rob the citizens of their free speech. However, although the assembly had become confused and tumultuous, Dion came forward and showed in his own defence that Sosis was a brother of one of the body-guards of Dionysius, and had been induced by him to raise confusion and faction among the citizens, since there was no safety for Dionysius except in their mutual distrust and dissension. At the same time, too, the physicians examined the wound of Sosis and discovered that it had been made by razure rather than by a downright blow. For the blows of a sword, by reason of its weight, make wounds that are deepest in the middle, but that of Sosis was shallow all along, and intermittent, as would be natural if he stopped his work on account of pain, and then began it again. Besides, certain well known persons brought a razor to the assembly, and stated that as they were walking along the street, Sosis met them, all bloody, and declaring that he was running away from Dion's mercenaries, by whom he had just been wounded; at once, then, they ran after them, and found no one, but saw a razor lying under a hollow rock in the quarter from which Sosis had been seen to come.
Well, then, the case of Sosis was already desperate; but when, in addition to these proofs, his servants testified that while it was still night he had left the house alone and carrying the razor, Dion's accusers withdrew, and the people, after condemning Sosis to death, were reconciled with Dion.
Related post: Impostors