Advice from David Paul Jones’s Rules of Cross-Examination, a British barrister who wrote over a century and a half ago
1. Except in indifferent matters, never take your eye from that of the witness; this is a channel of communication from mind to mind, the loss of which nothing can compensate. Truth, falsehood, hatred, anger, scorn, despair, and all the passions--all the soul--is there.
2. Be not regardless, either, of the voice of the witness; next to the eye this is perhaps the best interpreter of his mind. The mental reservation of the witness--is often manifested in the tone or accent or emphasis of the voice.
3. Be mild with the mild; shrewd with the crafty; confiding with the honest; merciful to the young, the frail, or the fearful; rough to the ruffian, and a thunderbolt to the liar. But in all this, never be unmindful of your own dignity. Bring to bear all the powers of your mind, not that you may shine, but that virtue may triumph, and your cause may prosper.
4. An equivocal question is almost as much to be avoided and condemned as an equivocal answer; and it always leads to, or excuses, an equivocal answer. Singleness of purpose, clearly expressed is the best trait in the examination of witnesses, whether they be honest or the reverse. Falsehood is not detected by cunning, but by the light of truth.
5. But in any result, be careful that you do not lose your temper; anger is always either the precursor or evidence of assured defeat in every intellectual conflict.
6. Like a skillful chess-player, in every move, fix your mind upon the combinations and relations of the game--partial and temporary success may otherwise end in total and remediless defeat.
7. Never undervalue your adversary, but stand steadily upon your guard; a random blow may be just as fatal as though it were directed by the most consummate skill; the negligence of one often cures, and sometimes renders effective, the blunders of another.
8. Be respectful to the court and to the jury; kind to your colleague; civil to your antagonist; but never sacrifice the slightest principle of duty to an overweening deference toward either.
9. Thus, as you rise to cross-examine a witness, you should be armed with the skill to adopt the style required for this particular witness and jury, the technique to search out the truth, the knowledge of guidelines that have developed over the centuries, and, most important, the wisdom to discern the proper combination of style and technique you need to serve well the consummate role of the cross-examiner--the truth giver.