Many of our clients request assistance when they are asked to render expert opinions in cases.  Often confusion exists as to whether to become involved, knowing that their opinions will be “dissected” through vigorous cross examination in a deposition and potentially at trial.  The answer lies in understanding that to be of value in a case, the presented expert testimony must generally be found relevant and reliable (in federal courts) or premised on methodologies, facts and data that are “generally accepted” within the given field of the expert (in Illinois courts). 

       Testimony is relevant if it is material to a genuine issue of fact.  A fact is material if, under the substantive law that is applied to the case, it is essential to the proper disposition of the case.  An issue is genuine if there is sufficient evidence on each side so that a rational trier of fact (like a jury) could resolve the issue either way.  In other words, relevant testimony is testimony that “fits” the issues that a jury must confront in order to decide which side prevails.

       Testimony is reliable if the expert’s opinions are based upon a methodology, science and expertise that satisfies a non-exclusive list of factors, such as whether the theory or technique be tested, whether the results have been peer reviewed and whether the technique has a known or potential rate of error.  In addition, it is also significant whether the theory has gained general acceptance in the relevant community.  Reliability focuses upon the expert’s principles and methodology and not the scientific conclusions they may generate.

       After expert testimony is given, the party to a lawsuit who opposes the expert may file a motion for summary judgment, even if the judge has already decided that the expert’s testimony is relevant and reliable.  Summary judgment is a legal concept meaning that there is no material issue of fact to be decided against the party who presented the expert for deposition.  This might seem surprising to the expert who believes that he is qualified, experienced in his or her field and able to testify regarding the issues for which he or she was retained. 

       In most situations, such a motion should fail because the expert’s testimony is relevant and reliable.  The only occasions where a summary judgment might be granted on contested facts is when the testimony does not satisfy elements of a party’s burden of proof (i.e., what a party needs to prove in order to obtain relief from a trier of fact), when the testimony goes against prevailing law, or when the testimony is to be heard by a judge who will act in place of a jury.  

       An expert whose opinions are found relevant and reliable on contested facts will know that his or her opinions will go to a jury to determine whether they are persuasive enough to enable the party who retains the expert to prevail in the lawsuit.