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.

In Colorado, the admissibility of expert witness testimony is governed by rules that are similar to the Federal Rules of Evidence. An individual may qualify as an expert witness if they possess specialized knowledge, skill, experience, training, or education that is relevant to the case at hand. Their testimony is considered admissible if it provides assistance to the judge or jury in understanding the evidence or in determining a contested fact. 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 their expertise in relation to the subject matter of the dispute. The judge serves as a gatekeeper, ensuring that only expert testimony that is pertinent and methodologically sound is presented to the factfinder. This gatekeeping role involves assessing the proposed testimony's relevance and reliability, considering factors such as the expert's qualifications, the methodology used, and the applicability of the expert's reasoning to the facts of the case.