Institutio Oratoria

On the other hand in the case of a witness who is reluctant to tell the truth, the essential for successful examination is to extort the truth against his will This can only be done by putting questions which have all the appearance of irrelevance. If this he done, he will give replies which he

thinks can do no harm to the party which he favours, and subsequently will be led on from the admissions which he has made to a position which renders it impossible for him to deny the truth of the facts which he is reluctant to state.