February 27, 2012

Effective Cross Examination of an Expert Witness

Jonathan Park

The renowned general Sun Tzu once wrote that "the victorious strategist only seeks battle after the victory has been won."  This maxim squarely applies to the cross-examination of an expert witness, especially since you should know the exact substance of the expert's testimony in advance and thus have an opportunity to carefully plan your attack.  The following tips will help you do just that.


The effective cross-examination begins long before you first question the opposing expert in court.  At the expert's deposition, it is absolutely critical that you "box in" the expert regarding the exact opinions that he/she intends to give at trial, the basis for those opinions, and any assumptions the expert made in reaching those opinions.  At the end of the deposition, remember to use a catch-all question such as: "Other than the opinions you have already expressed today, are there any other opinions that you intend to give at time of trial?"  This should eliminate any surprises in the expert's testimony in court.


Not all experts are created equal.  Make sure to carefully research the expert's qualifications, community standing in the expert's own field, prior testifying experience.  It is likely this is not the expert's first time serving as an expert witness and/or testifying in court.  Prior cases involving the same expert can be a goldmine of information.  In a recent matter, I performed a basic search and discovered two different appellate cases specifically rejecting the expert's testimony because he had used an incorrect methodology - the same methodology he was trying to apply in my matter.


You should know the expert's report inside and out - every chart, figure, footnote, and how the different parts of the report interrelate.  In particular, you should know every error great and small in the report.  The expert should not be guiding you through his report (and opinions) during cross-examination.  Instead, you should be methodically leading the expert to reveal the errors or weak points in his/her report.


Cross-examination of an expert is unique because you should know the exact substance of the expert's testimony in advance and thus have an opportunity to carefully plan your attack.  It is essential, therefore, to prepare a thorough cross-examination outline with direct references to the expert's deposition testimony and report.

In preparing your cross-examination outline, you should generally focus on only three or four key points of attack.  You may confuse (or worse, bore) the judge/jury with anything more.  There are several potential areas of weakness:

·         Poor qualifications and/or lack of expertise

·         Rushed/incomplete analysis

·         Insufficient data or information to perform analysis

·         Wrong assumptions

·         Bias

·         Incorrect methodology

·         Inaccurate work

Your cross-examination questions should be direct and not leave the expert any "outs."  Do not underestimate the ability of a seasoned expert to deflect your attacks.  Typically, you should seek "yes" or "no" answers from the expert.  If you are going to set a trap, think through all the possible responses and explanations and have follow up questions for each of the different ways the expert might answer.


It is crucial to listen carefully during the direct examination of the opposing expert.  Do not assume that the expert will simply repeat what he/she said at deposition or in his/her report.  Be attentive for any changes to the expert's opinions, basis for opinions, or assumptions.  You may need to quickly revise your own cross-examination to incorporate the expert's changed testimony.

Lastly, be flexible during the actual cross-examination.  Your cross-examination outline is not a script.  Follow the natural course of the examination.  That being said, keep track of the three or four key points you need to address and return to them, in turn, as appropriate.


Jonathan Park