Institutio Oratoria

Fortune sometimes is so kind that a witness gives an answer involving some inconsistency, while at times (and this is a more frequent occurrence) one witness contradicts another. But acute examination methodically conducted will generally reach the same result which is so often reached by chance.

There are also a number of points strictly irrelevant to the case on which questions may be put with advantage. We may for example ask questions about the past life of other witnesses or about the witness' own character, with a view to discovering whether they can be charged with some disgraceful conduct, or degrading occupation, with friendship with the prosecutor or hostility toward the accused, since in replying to such questions they may say something which will help our cause or may be convicted