A relatively small but critical part of the forensic expert’s responsibilities involves testifying about the scientific basis of analyses, findings, and conclusions in court or during deposition. Credible experts must prepare thoroughly, demonstrating a command of the scientific knowledge associated with their areas of expertise. In addition, they must have a thorough understanding of the procedures of the court and the evidence admissibility standard in their jurisdiction. All experts must be open in their dealings with attorneys, willing to discuss their findings and conclusions within the bounds of the trial practice for the type of case in which they are serving as experts. While the “rules” may vary under civil and criminal law and whether the expert appears for the state or defendant in a criminal case, that expert must show no bias in action or explanation, but demonstrate scientific objectivity during his entire involvement in a case. Credibility involves the expert’s ability to communicate with the trier of fact; better communication skills ensure the “audience” does not get lost in what the expert is trying to say or how the expert is saying it. Demeanor also communicates something to the jury, so the credible expert will be professional in appearance and speak confidently without being haughty.

During a recent webinar offered by Forensic Magazine, I had the opportunity to discuss in greater detail some of those factors that I believe make for a credible expert witness. Among the many questions received during this webinar and in expert witness classes and consultations, several issues repeatedly arise. These questions reflect a desire of experts from all disciplines to provide useful, scientifically accurate information to the trier of fact. I would like to examine the 5 most common questions about testimony and being an expert witness that I have received in recent years.

Question 1: What do I do if the attorney who has called me to testify refuses to meet with me before I testify?
Meeting with the attorney, especially the attorney who is calling you to testify, is essential to your job as an expert witness. Only the attorney can explain her overview of the case to you and what she sees as the value of your testimony. The attorney should outline the questions she will ask in the sequence that she will ask them. This gives you an opportunity to make sure that the attorney knows what you are going to say and how it will impact her case. A good attorney will always find time to talk to her witnesses, even if for a short period of time. When attorneys don’t meet with you it may be because they feel uncomfortable with the subject matter or believe you know much better what to say. However, how smoothly your testimony goes may be totally dependent on the approach and questions the attorney asks. You cannot be properly prepared for your testimony if the attorney does not review her strategy and your information or conclusions prior to your taking the stand. If you receive a subpoena or phone call that your testimony is required, immediately request to speak with the attorney. Set up a time when you can meet prior to your testimony. If the attorney says that she is too busy or surrounded by materials and items that require more immediate attention, offer to meet at the day and time most convenient for the attorney. Explain the benefits to you and why you need the meeting. As much as possible, also stress the benefits to the attorney. While you may only get a few minutes to provide an overview, this is better than no meeting at all. Eventually, the benefits of those meetings will be seen in the more organized flow of information to the jury.

A pre-trial meeting provides experts with some understanding of how the case will proceed while they are testifying. In many cases the opposing attorney may also contact you. This is a good thing. If you are working for the state in a criminal case, you should welcome a meeting with the defense attorney. The attorney will have the opportunity to review the tests you did and the significance of the results obtained in a much less formal manner than when you are testifying on the witness stand. This is a perfect opportunity for you to educate the attorney. It also shows that you are open and unbiased. Since bias is the most common method used to attack the credibility of a forensic expert, any opportunity to let the attorney see how unbiased you are can always be helpful. This meeting with counsel before trial often reaps many benefits. You may even find your testimony is less arduous.

I was recently asked if it was alright to talk to the “opposing attorney” (the lawyer who did not call you to testify) after you begin testifying, such as during a break. My response was an energetic, “Of course!” If you find yourself on a break during testimony and you haven’t spoken with that attorney previously, introduce yourself and ask if the attorney has any questions. Usually, lawyers will not have any questions, but will remember that you were available to them outside the formal setting of the courtroom. This willingness to share your knowledge and conclusions goes a long way to make the process less adversarial for the witness.

Question 2: Should you even say “I don’t know” on the witness stand? Doesn’t it make you sound inadequate as an expert?
It goes without saying that the expert will understand the scientific basis of the testing that was done. However, even the most educated and experienced persons have gaps in their knowledge and experience. In most cases, what you don’t know will have no effect on the outcome of a trial. The exception to this is if you admit you are not familiar with a certain basic process or fact that is an essential part of your area of expertise. The expert should also be familiar with other techniques and procedures that may be conducted in other laboratories. These should never be in the “I don’t know” category. However, certain activities that took place before the expert received the evidence, subsequent activities and collateral matters may not be familiar. If you are asked a question and you do not know the answer, you should answer clearly, “I don’t know.” Never speculate. Never say “I imagine.” Never try to reason out the “best” answer. This can lead to disastrous results. Once you say you do not know the answer to a question, the attorney can repeat that question only so many times before the court will stop the repeated questioning, the other attorney will object, or the jury will get bored or annoyed. If you are thoroughly prepared, the situations that arise where you must express a lack of knowledge should be minimal and logical based on your role in the case.

Question 3: What do I do if asked a question outside my field of expertise?
It is well known that many attorneys are not thoroughly versed in the different forensic disciplines. In addition, lawyers may not grasp the subtle boundaries of a witness’s expertise. As with the “I don’t know” question, the best approach is to be honest and straightforward. If asked a question concerning a topic that is different from or tangentially related to your expertise, merely restate your expertise and that the question is outside your area. There is no need to explain further. The attorney may attempt to ask you the question in several ways, but just continue testifying that the subject is outside your expertise. Ultimately, you will appear more credible to the jury if you continue to insist on limiting the questions to your knowledge base.

Question 4: How do you correct a fact or conclusion that has been misstated by the attorney?
Sometimes attorneys will misstate your testimony or conclusions hoping to catch you in a contradiction or to provide information to support their cases. Usually, however, these errors are not intentional and may be misspoken or misunderstood information. Once again the best solution is the most straight-forward. Before answering the question, restate the premise correctly. For example, if the attorney says that the fiber analysis resulted in a match of two fibers, the expert could respond, “We do not say that fibers are “matched” by these methods, but results of these analyses did show the fibers to have similar microscopical and instrumental characteristics.” This restates the limitations of the tests for the trier of fact and prevents the witness from agreeing tacitly to the use of inappropriate terms. Once expert witnesses have finished testifying, they cannot control the language used by attorneys during other court proceedings. While still on the stand, however, it is the expert’s responsibility to see that results and conclusions are not misstated or mischaracterized by counsel.

Question 5: What are the most common tactics used to discredit a witness?
There are several common methods that attorneys rely on to impeach a witness. Of course, any obvious untruth will be immediately pointed out to the jury. Misleading or falsified qualifications, for example, will be uncovered by diligent attorneys or pointed out by other experts involved in the case. It is imperative that the expert state qualifications correctly and without embellishment. There have been experts who have been removed from their positions and even charged with perjury for claiming degrees and training that they did not receive.

Impeaching a witness using previous statements or testimony is often used if the witness has provided an interpretation of the facts or findings in a way that is different from previous testimony in the current or previous cases. There may be a reasonable explanation for this difference, but the expert must be aware of the apparently contradictory statements and be prepared to explain why the current case differs from prior circumstances. If the expert cannot offer such an explanation, the jury will likely consider the testimony biased and may even believe the expert is untruthful. Both are disastrous for the expert witness.

A witness who is obviously biased will be challenged consistently and extensively by an attorney. Since expert witnesses are supposed to be unbiased as they assist a jury in understanding a fact at issue, experts who obviously interpret data with a bias will be brought to task. Sometimes the experts may not even be aware of the bias inherent in their conclusions; this so-called contextual bias and its effects on expert analysis has been the subject of extensive study in recent years. The credible expert will work diligently to evaluate a case without bias, establish procedures to account for contextual bias, and remove language from reports and testimony that may inappropriately favor one side of the dispute over another.

As these questions show, most experts want to provide accurate testimony. They want to observe appropriate legal protocols while maintaining scientific integrity. This is not really a difficult thing. Credible experts will be well prepared for court, have extensive knowledge of their subject matter, and understand their role in court proceedings. By presenting their findings in a clear and concise manner without concern about which “side” will benefit from their answers, credible expert witnesses benefit the trier of fact and the justice system.

Elaine M. Pagliaro, M.S., J.D. is Director of Research and Grants at the Henry C. Lee Institute of Forensic Science. She has worked many years as a forensic scientist and adjunct faculty member at several colleges and universities. Henry C. Lee Institute of Forensic Science, 300 Boston Post Road, West Haven, CT 06516;