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 Colorado, expert witness testimony is governed by rules similar to those outlined in the Federal Rules of Evidence. An individual may testify as an expert if they have specialized 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 the admissibility of the expert testimony to ensure that it is pertinent and methodologically sound. The judge's role is to prevent unreliable or irrelevant expert testimony from being presented to the jury. This gatekeeping function is crucial to maintaining the integrity of the judicial process and ensuring that decisions are based on credible and pertinent expert insights.