It often happens in popular states that accusations are public and that any man is at liberty to accuse whomever he wishes. For this reason, laws have been made for the defense of citizens’ innocence. In Athens, the accuser who did not have a fifth of the votes for him paid a fine of a thousand drachmas. That was the sentence of Æschines, who had accused Ctesiphon.  In Rome, the unjust accuser was stigmatized  by the lettre K  imprinted on his forehead. Guards were assigned to the accuser so he would be in no position to corrupt the judges or the witnesses. 
I have already mentioned that Athenian and Roman law that allow the accused to withdraw before the judgment.