Role of An Expert Witness
Expert witnesses are allowed under the rules of evidence to “help the trier of fact to understand the evidence or to determine a fact in issue” (See Federal Rule of Evidence 702). The trier of fact in a jury trial is the jury and the trier of fact in a bench trial is the judge. In other words, the role of an expert witness by rule is to teach the judge or jury.
The role of an expert witness often expands beyond teaching the judge or jury. For example, expert witnesses may be asked to assist in preparing questions the retaining counsel will use to examine opposing expert witnesses. Such assistance is often crucial as retaining counsel may not have the technical knowledge to formulate the right questions.
It is important to note that the proper role of an expert witness is not that of serving as an advocate for the party that is paying them. Expert witnesses who appear to be hired guns or advocates for their clients rapidly lose credibility. The most effective expert witnesses call cases as they see them. They are advocates for their opinions, not the party who is paying their fees.
For more information on the role of an expert witness, a great resource is SEAK, Inc.’ text The A-Z Guide to Expert Witnessing.