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 Iowa, expert witnesses are individuals who, due to their knowledge, skill, experience, training, or education, may provide testimony in legal proceedings if their specialized knowledge can help the court understand the evidence or resolve a disputed 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 the witness's expertise in relation to the subject matter of the case. The judge serves as a gatekeeper, assessing the appropriateness of the expert's testimony, ensuring that it is reliable and pertinent to the case at hand. The judge has the discretion to admit or exclude expert testimony, and this decision is crucial because it influences what the jury or judge can consider when making factual determinations.