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 Florida, the admissibility of expert witness testimony is governed by the Florida Evidence Code, specifically Section 90.702. This statute allows for a witness who has specialized knowledge, skill, experience, training, or education to testify in the form of an opinion or otherwise if: (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case. The determination of whether a witness qualifies as an expert and whether their testimony is admissible is made by the judge, who serves as a gatekeeper. The judge must ensure that the expert's testimony is not only relevant but also based on a reliable foundation. This gatekeeping role is informed by the Florida Supreme Court's adoption of the Daubert standard, which requires the judge to assess the reliability of the expert's methods and the applicability of those methods to the facts of the case. The goal is to prevent unreliable expert testimony from being presented to the jury.