American Bar Association
General Practice, Solo, and Small Firm Division



Cross-Examining Expert Witnesses

Perhaps the best-known metaphor for cross-examining an expert witness is put forth by renowned trial lawyer Michael E. Tigar:

[There are] three main themes of effective cross-examination of experts.

First, cross-examination of an expert usually will resemble peeling an onion, exposing layer after layer of weakness, error, and fallacy...In trial your objective must be to provide jurors inclined to support you with the evidence and argument they will need to carry the day during deliberations. The more complex the case, or the longer the deliberations, the more important is this principle.

In cross-examining an expert this principle requires that your attack be patient, systematic, and measured. True, it will often be necessary to wait until final argument to assess the entire impact of your cross. But jurors should carry away from the cross-examination itself the abiding conviction that they could, if called upon, argue against the expert’s conclusions.

The second theme of cross must be your theory of the case. This is often no more than the obverse of the proponent’s desire to use the expert as a summary witness for the theme of his case. Sometimes, the expert will be nearly the whole case...As you build the cross, be sure to have plenty of reference points at which you challenge the expert not only to make a particular concession, but go on to note the impact of that concession on the case as a whole.

The third theme...requires an eye on the state of the record in the unhappy event that you must take an appeal...The judicial tendency to simplify matters by letting the jury sort things out has been criticized by appellate judges...and may serve as a basis for appeal.

One cannot predict where the appellate court will take its bite out of an expert, if it is persuaded to reverse. You must prepare for all of several live possibilities. The expert may be one whose opinions are available to the highest bidder. There may be...a fatal flaw in the proponent’s case. The opinion may self-destruct on detailed analysis. The expert’s opinion may rest upon an assumed factual basis that the jury demonstrably rejects. One must, in short, draw from cross-examination the basis for any and all of these arguments...

The initial stages of cross-examination should focus on areas in which the expert must agree with you. Begin with matters on which there is ample common ground between the proponent and opponent. This illustrates what I call the "theory of minimal contradiction." That is, not all the opponent’s witnesses are lying about everything, or at least it is difficult to persuade a jury that they are. Instead, we try to point out and highlight the true area of disagreement and keep the jurors’ attention focused there.

Having exhausted areas of agreement, turn to attack qualifications, conclusions, and/or underlying facts, depending upon the strength of your position in these areas.


Source: "Cross Examination of Expert Witnesses," by Michael E. Tigar, in Expert Witnesses , edited by Faust F. Rossi. Copyright © 1991 American Bar Association. All rights reserved. Reprinted by permission.



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