(d) the expert has reliably applied the principles and methods to the facts of the case.)' (c) the testimony is the product of reliable principles and methods and (b) the testimony is based on sufficient facts or data (a) the expert's scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue 'A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if:

Rule 702 of the Federal Rules of Evidence, Testimony by Expert Witnesses, states that

On direct examination, the strengths of an opinion reached under Daubert criteria become a 'teaching moment' for the trier of fact, because it will be founded on the science of mental health assessment. Being familiar with the Daubert criteria enhances effectiveness in challenging a mental health expert's opinion, whether on voir dire or cross examination. Also, extensive case law presently exists as to specific issues. In most cases where an attorney is considering a 'Daubert challenge,' a contemporaneous and up-to-date literature search is indicated. The testimony of a mental health expert rendering an opinion using criteria which does not meet Daubert standards is weakened by the implication that it is not based on 'sound science.' In some instances, for example, a mental health expert uses an approach where there are no peer-reviewed studies or methods, such as when psychologists compose their own neuropsychological test batteries. Daubert specifies that adequate scientific support and method and a known error rate must exist. The effect of Daubert has been to limit expert testimony to opinions which are based on a scientific foundation. The judge of the court rules on the admissibility of the expert opinion.

In order for a medical opinion to be admissible as evidence in civil, criminal and administrative cases, the basis of the opinion must fulfill either the Daubert Criteria or the Frye test, depending on the jurisdiction.

Expert witness psychologist