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 Oklahoma, expert witnesses are individuals who, due to their knowledge, skill, experience, training, or education, may provide testimony in legal proceedings if their expertise can help the judge or jury understand the evidence or resolve a disputed fact. The decision to qualify someone as an expert witness 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, determining the admissibility of expert testimony by assessing whether the testimony is sufficiently reliable and pertinent to the issues at hand. This gatekeeping role is crucial to ensure that only credible and relevant expert evidence is presented to the factfinder, whether it be a judge or a jury.