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 Texas, expert witnesses are individuals who, due to their knowledge, skills, experience, training, or education, may provide testimony in legal proceedings if their specialized knowledge can help the judge or jury understand the evidence or resolve a disputed fact. The qualification of an expert witness is not determined by a strict formula; rather, there must be an appropriate match between the expert's expertise and the subject matter of the case. The decision to qualify a witness as an expert rests with the trial judge, who serves as a gatekeeper to ensure that only reliable expert testimony is presented. This gatekeeping function is guided by rules of evidence and case law, including the Daubert standard, which assesses the methodology and principles underlying the expert's testimony for relevance and reliability before it is admitted for the judge's or jury's consideration.