Originally from Take the Witness: Cross-Examination in International Arbitration, 2d Ed.

Adverse expert witnesses, in arbitration as in litigation, fall into two main categories. One is the honest but mistaken professional.  The other is the paid liar. Fortunately, one tends to encounter more from the former category than the latter, but how one approaches cross-examination of the expert, and the odds of succeeding, depend to a significant degree on correctly identifying which category the expert falls into. In addition to the meticulous preparation on which the success of any cross-examination depends, one’s approach must also take into account the ways in which arbitration procedures differ from litigation, such as the practice of “hot-tubbing” expert witnesses.

I.  Attacking the Paid Liar

There is not much to be done with the paid liar other than to attack.  The nature of the attack will, of course, depend on what the cross-examiner has to work with.  Some experts’ credentials may be shaky or, with luck, even fraudulent.  Some may have a demonstrable bias. Others may have relied on distorted data, either by cherry-picking from what is in the record or relying on data that can be demonstrated to be unreliable. Others may have left themselves open to attack on gaps or fallacies in the logic with which they justify their conclusions. Once one reaches the conclusion that the expert is simply making up answers to support the case of the party that retained him, or her, there is no substitute for an aggressive cross-examination designed to help the arbitrators reach the same conclusion.