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Law 101: Legal Guide for the Forensic Expert

Exercising Caution About Opinions, Omissions and Responses at Deposition

During a deposition, the expert should be presented as an expert only in the expert's field of expertise. An expert's training and experience will be carefully examined. Exaggerations or deficiencies can minimize the value of any testimony about the subject at hand. An expert should advise counsel to seek additional experts if the expertise is not adequately comprehensive for the case or subject matter for which the expert is being consulted or retained.

The expert should remember that theories and opinions are only as valid as the facts upon which they are based. Therefore, the expert should be prepared to identify every document, note, memorandum, research study, evidence test result, photograph and transcribed conversation that was used in rendering his opinion.

Frequently, an expert will render an opinion at the deposition. When asked what facts and/or professional tests or publications were relied upon to render such an opinion, the expert may tend to abbreviate the response or may forget items.

At trial, the expert will be asked for the opinion and what items were relied upon to render the opinion. If the trial response differs from the deposition response, the expert can explain that such omissions of material facts were due to the expert's summarization or an honest memory lapse at the deposition.

These omissions may lead to an expert's impeachment at trial, however, and are better avoided. A preferable response is to answer questions completely during deposition, avoid summarizing for the sake of brevity (unless instructed to do so by the proffering attorney), and be so well-prepared that no memory lapses occur regarding important items.

The expert's opinions may be sound, but if they cannot be supported by identifiable, admissible evidence and test results based upon facts developed in the case, the expert's theories may be rejected by the jury and limited by the court. At deposition, an expert may also be asked to render additional opinions that have not been previously provided or for which the expert may be inadequately prepared. The expert should discuss this possibility with counsel before the deposition. The opinion rendered before the deposition was probably based on evidence testing and a review of reports, facts and relevant scientific literature and was provided only after thorough review and with due consideration. The expert should never feel pressured to render an opinion if not prepared to do so or if not fully informed on the facts and evidence.

The expert will most likely be asked by opposing counsel what communications the expert had with counsel before the deposition. This is not unusual, and the expert should prepare for this question with counsel in advance so that the answer betrays no awkwardness.

Despite an expert's background and knowledge, there is no obligation to educate the deposing attorney about the subject matter of the case or litigation. The expert should answer the attorney's questions directly and succinctly without volunteering information. 

If the attorney neglects to ask certain questions about specific areas during the deposition, the expert is not precluded from testifying about those areas later. Direct examination at trial is the proper place for the expert to address key areas that may have been ignored (intentionally or unintentionally) during deposition.

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