The conclusion to our series on How to Be an Effective Expert Witness in Court.

The final function of an expert witness is to testify live at trial. This is the culmination of all the work that has gone on before. In many ways it is the most important thing an expert witness does. It is your chance to influence the judge and jury who will ultimately make the key decisions in the case leading to the final outcome. The reality is that the vast majority of cases settle before trial. Thus, even if you've been involved as an expert in many cases, it is likely you have limited experience testifying as an expert witness at trial. Nevertheless, all your work in a case must be premised on the possibility you will be called to testify at trial. You must be prepared to meet the challenges of trial testimony, and you must anticipate them as you go through the other steps discussed in the prior articles in this series. In many cases what you say and do at trial will make or break the case.

It is helpful to understand the overall process before discussing individual aspects in detail. The process begins with meetings with your attorney to prepare for your testimony. The number of meetings and the extent of preparation will vary depending on the importance of your testimony to the case overall. You will define the nature and scope of your testimony, discuss the exhibits you will utilize at trial, and determine how best to deliver the information the attorney wants you to convey to the jury. Typically you will rehearse your testimony and be subject to a mock cross examination. The goal is to prepare you to testify in such a way that no question will be asked of you at trial that you have not already considered and to which you have not already formulated an effective response. By the time you get to trial, if your attorney has done his or her job properly, there should be no surprises.

Once the day of trial arrives you will begin with direct examination. This is your opportunity to tell what you've done and what you know the way you and your attorney want to present the testimony. Direct examination involves responding to open ended questions from your attorney. The attorney will be limited in the way he or she can ask questions; leading questions will not be allowed (unless they try, and the other side fails to object). The norm is to limit your testimony to direct questions which require you to provide a narrative response. Leading questions, i.e., those requiring only a "yes" or "no" answer, are for the opposing attorney and should be encountered only during cross examination. One of the most important parts of trial preparation is the time spent educating you on how to deal with leading questions, and to help you anticipate how they will be used against you. If the attorney fails to raise the issue with you during trial preparation you should be sure to raise it on your own.

Direct examination is your opportunity to impress the jury with your qualifications. You will also want to demonstrate the thoroughness of your work so your testimony will be seen as authoritative and your ultimate opinions worthy of belief. You will frequently be called upon to do more than testify about what you have done. Often your primary role will be that of an educator, teaching the jury the technical subjects they need as a foundation for understanding your ultimate theories and opinions. It can be a challenge to explain highly technical subjects to a group of lay people. A common rule of thumb is to assume you are teaching a group of eighth graders in order for you to pitch your presentation to the right level of sophistication and to have the broadest impact on the majority of the jurors. You must never forget that technical expertise is useless if you cannot explain the concepts in simple enough terms that the jury understands them. By the time you finish direct testimony you should have demonstrated your competence, explained what you did in the case, educated the jury as needed, and offered your ultimate opinions on the subjects about which you are qualified to respond.