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 Tennessee, the admissibility of expert witness testimony is governed by rules that are similar to the federal Daubert standard. Under Tennessee law, a witness may qualify as an expert based on their knowledge, skill, experience, training, or education, and may testify if their expertise will help the court understand the evidence or determine a fact in question. The determination of whether a witness is qualified as an expert is not based on a strict formula but rather on the relevance and reliability of the expert's knowledge in relation to the subject matter of the case. The judge serves as a gatekeeper, assessing the reliability of the expert's testimony and ensuring that only pertinent and dependable expert evidence is presented to the jury. The judge has the discretion to exclude expert testimony that is deemed unreliable or not applicable to the case at hand. This gatekeeping role is crucial to maintaining the integrity of the legal process and ensuring that decisions are based on sound and credible expert analysis.