Institutio Oratoria

There is no doubt who administered the draught, and, if it was poison, there is no question as to the author: but the problem as to whether the draught was poison can only be decided by arguments drawn from the character of the accused. There remains a third type of conjectural case where the fact is admitted, and the only question is as to the author. It is unnecessary for me to quote examples, since such cases are of frequent occurrence. For example, it may be clear that a man has been killed or that sacrilege has been committed, but the person accused of the crime may deny his guilt. It is from such circumstances that cases of mutual accusation arise, where it is admitted that the crime has been committed, but each party charges the other with being the author.