A witness who qualifies as an expert because of knowledge, skill, experience, training, or education may testify as an expert if scientific, technical, or other specialized knowledge will assist the judge, jury, or other factfinder to understand the evidence or determine a contested fact issue.

But there is no rigid formula for determining whether a particular witness is qualified to testify as an expert. Generally there must be a fit between the subject matter at issue and the expert witness’s familiarity with the subject matter. And this determination is made by the judge, who acts as a gatekeeper to only allow reliable expert witness testimony to be heard and considered by the judge or jury—and to exclude such testimony when it is not reliable.

In Kansas, the admissibility of expert witness testimony is governed by Kansas statutes and case law, which align with the principles of the Federal Rules of Evidence. An individual may testify as an expert if they have the requisite knowledge, skill, experience, training, or education that will help the court understand the evidence or determine a fact at issue. The determination of whether a witness qualifies as an expert is not based on a strict formula but rather on the relevance and reliability of the witness's expertise in relation to the subject matter of the case. The judge serves as a gatekeeper, assessing whether the expert's testimony is sufficiently reliable and relevant to the issues at hand before allowing it to be presented to the jury. This gatekeeping role involves considering factors such as the methodology used by the expert and whether it is generally accepted in the relevant field. The goal is to ensure that only trustworthy expert testimony is considered by the factfinder, whether it be a judge or a jury.