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 Rhode Island, as in many jurisdictions, the admissibility of expert witness testimony is governed by rules that require the expert to have specialized knowledge, skill, experience, training, or education that is pertinent to the case at hand. The purpose of expert testimony is to help the judge or jury understand complex evidence or resolve issues that require specialized knowledge. 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 dispute. The judge serves as a gatekeeper, assessing whether the proposed expert testimony is sufficiently reliable and relevant to the case before allowing it to be presented to the factfinder. This gatekeeping role involves ensuring that the expert's methods are properly applied to the facts of the case and that the testimony is based on more than mere speculation or conjecture. Rhode Island courts follow the principles outlined in the Federal Rules of Evidence and relevant case law to guide these determinations.