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 Maryland, expert witnesses are individuals who, due to their knowledge, skill, experience, training, or education, may provide testimony in legal proceedings if their insights can help the judge or jury understand the evidence or resolve a disputed fact. The state does not adhere to a strict formula for qualifying an expert witness. Instead, there must be a relevant connection between the witness's expertise and the subject matter of the case. The determination of whether a witness is qualified to testify as an expert is made by the presiding judge. This judge serves as a gatekeeper, ensuring that only reliable expert testimony is presented to the decision-makers. Maryland courts typically follow the guidelines established in the case of Daubert v. Merrell Dow Pharmaceuticals, Inc., which sets the standard for admitting expert scientific testimony, although Maryland has not formally adopted the Daubert standard. The judge's role is to evaluate the relevance and reliability of the expert's proposed testimony, considering factors such as the methods used, the peer review and publication of the work, the potential rate of error, and the acceptance within the relevant scientific community.