Before 1993, the courts admitted expert testimony in lawsuits if the theory being presented by the expert had general acceptance in the scientific community. An expert witness is a person with specialized education, training, or experience in a technical field. An expert is allowed to give an opinion about a technical issue in a lawsuit. Under the Federal Rules of Civil Procedure, the general acceptance standard became somewhat relaxed. Concern grew that expert scientific testimony was increasingly based on "junk science" instead of sound scientific methodology. Junk science refers to novel scientific theories that are based on questionable data or suppositions that have not been scientifically proven.

Daubert Standard for Expert Testimony

In 1993, the United States Supreme Court established standards for admitting expert testimony when it decided Daubert v. Merrill Dow Pharmaceuticals. In Daubert, a minor child and his parents, together with another minor child and his mother, sued a drug company. They alleged that the children's birth defects had been caused by the company's prescription drug, which had been taken by the mothers during pregnancy.

The Court held that scientific evidence had to be based on scientific validity in order to be reliable. As a result of the Daubert decision, a scientific theory has to have been tested and subjected to peer review and publication to be admissible at trial. The rate of error has to be shown, and there must be standards controlling any research on the theory. Finally, the theory has to be generally accepted in the scientific community.

Standard of Review for Exclusion of Expert Testimony

After Daubert, the federal courts of appeal used different standards when reviewing a trial judge's decision to admit or exclude expert testimony. In 1997, the United States Supreme Court held that the proper standard of review for a trial court's exclusion of expert testimony was the abuse of discretion standard. A trial judge's discretion must be exercised fairly and impartially. That discretion is abused if there is no evidence to support the judge's decision or if the judge fails to apply the correct law or makes an erroneous finding of fact.

Daubert Standard Applies to Both Non-Scientific and Scientific Expert Testimony

In 1999, the United States Supreme Court again considered the Daubert standard in the case titled Kumho Tire Co. v. Carmichael. The Court held that the Daubert standard applied to non-scientific expert testimony as well as scientific expert testimony. Thus, the trial judge may apply the Daubert standards in evaluating the reliability and relevance of non-scientific expert testimony. This means the trial judge has broad discretion in applying the Daubert standards to an expert's testimony based on personal experience or technical studies. The goal should be to ensure that an expert's testimony in court is characterized by sound intellectual evaluation.

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