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Expert Witnesses

Evaluating and Instructing Expert Witnesses

Dealing with an expert witness is a form of art. Experts’ involvement in litigation is becoming more widespread, while the standards for evaluating their testimony is as vague as ever. Experts need to understand what goes on in the courtroom, and this guide is designed as a brief overview of some concepts you should follow in order to adequately train your expert.

1. Qualifications.

An expert's resume or CV (curricula vita) needs to be current. It should show that the expert continue to study in their field and is gainfully employed, otherwise the expert's knowledge may be called into question as old and unpracticed, and his motivation for testifying questioned as simply money motivated. The resume should be comprehensive and provide all of the expert’s degrees and most of his or her scholarly articles. Obviously, the resume should reflect experience and expertise in the area upon which he or she will be testifying. For instance, if the expert will be testifying about DNA results, they should show experience working as a geneticist or in an appropriate lab, not simply that they are a general practitioner doctor with a generalized knowledge of DNA.

2. Confidentiality

Attorneys need experts that they know
they can trust to keep quiet. Many jurisdictions have rules and case law that provide what can and cannot be disclosed in the preparation of experts and their reports. Even so, all documentation should be treated as if it may be disclosed to the adverse party at some point. Candid discussions should be done face to face or, in some instances, over the phone (though phone records may be discoverable), and not via email or letter. If an expert is unable to comply with these requirements, he may jeopardize the entire case and it may be wise to retain a different expert.

3. Assumptions

Experts should form their opinions based on evidence which they have been able to observe for themselves. If an expert is relying on representations made to him by the client, the opinions will likely be biased, the foundations are absent, and the testimony may even be excluded in some instances as hearsay. For that reason, in preparing to testify, the expert should state all of their assumptions and describe in great detail their methodology. If they are relying on a third party laboratory to test materials that will form part of their opinion, they should state the qualifications of the laboratory in their expert report. If they are relying on scientific literature, manuals or books, make sure they have reviewed the most current editions. Science changes and develops over time with new findings, and nothing would be more detrimental to a case dependent on expert testimony than to find that your expert relied on a theory that has since been disproved or called into question.

4. Read the Expert's Report

The basis of your expert’s oral testimony is contained in his report. If oral testimony deviates from the report it could call the expert's credibility into question. Similarly, if words such as “may” are used, it opens the door of alternative possibilities when being cross-examined. In many instances, the expert will be ethically obligated to provide alternative theories, if they exist, and if that is the case you should be aware of these theories and be able to account for them before trial. To the extent that the expert is capable, ask him to use definitive words such as “shall,” “cause,” “conclusively” and “the result of” to avoid any suggestion of equivocation.


Typically a report is authored by one individual, as opposed to a group. However, some experts may head up a company, a lab, or other facility where others have contributed information upon which the expert's opinion is based. If that is the case, be sure that all who contributed to the report share a consensus of opinion as to the expert's findings. If there is dissent within the group, then that should be disclosed before the report is submitted for consideration.

6. Critiquing Other Experts

Since experts are usually not eyewitnesses to the events of a particular case, they may be present during the entire proceeding, and often counsel will ask them to attend during the opposing parties’ expert evidence to provide help on cross-examination and comments about the opposing expert's methods. If the expert is not going to be available during the duration of the trial or is uncomfortable commenting on another professional's work, this should be disclosed prior to preparing the report.

7. Prepare for Cross-Examination

The most difficult part of a good expert's job is holding up under cross-examination. Leading questions, misleading suggestions, and other tricks of the attorney's trade can have even the most seasoned expert flustered at times. A well prepared expert will have been coached on these techniques and allowed to practice responding to these types of questions. Similarly, the expert will not guess where counsel is going, nor attempt to avoid answering questions. Answers should be brief and to the point. The best experts tell a story on the stand, and make that story interesting and topical through references that the
judge and jury can understand. The more complicated an explanation, the more likely the expert is going to lose the attention of the fact finders and the more room he gives the opposing counsel to ensnare him in a verbal trap of his own making. The best expert testimony can be reduced in its entirety to between one and three sentences, possibly even a syllogism.

8. Payment

Experts are being paid for a service, but there are limits. Often the case rests upon the expert's testimony, true, but the expert should never bill on a basis that will impair their objectivity, such as a contingency fee. A retainer should be hourly and reflect industry standards and expertise.

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Disclaimer: While every effort has been made to ensure the accuracy of this publication, it is not intended to provide legal advice as individual situations will differ and should be discussed with an expert and/or lawyer.

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