A Daubert motion is a specific type of motion in limine. It is raised before or during trial, to exclude the presentation of unqualified evidence to the jury. Daubert motion is used to exclude the testimony of an expert witness does not possess the requisite level of expertise or used questionable methods to obtain data.
Daubert motion is the outcome of 1993 Supreme Court case, Daubert v. Merrell Dow Pharms., 509 U.S. 579 (U.S. 1993). Rules 702 and 703 of the Federal Rules of Evidence govern the admission of scientific evidence in federal court. The rules allow expert witnesses greater leniency in their testimony because it is presumed that the expert will have a reliable basis in knowledge and expertise in his field. The court in Daubert required that trial judges act as a gatekeeper and determine the scientific validity of scientific evidence before admitting it. The guidelines in the decision is now been expanded to include technical and specialized knowledge testimony as well.
The testimony of an expert witness has to pass two tests for a judge to accept:
- Empirical testing: the theory or technique must be falsifiable, refutable, and testable.
- Subjected to peer review and publication.
- Known or potential error rate.
- Whether there are standards controlling the technique’s operations.
- Expert’s qualifications.
- Technique and its results be described with plain meaning.
The relevancy of a testimony is subject to the type of the question. For example, an astronomer is an expert witness to tell the jury if it was a full moon on the night of a crime. However, the expert witness cannot be used to tell the jury that the defendant went lunatic because of that unfortunate moon phase. The judge must act as a gatekeeper to rule out bad testimony.
After the decision in Daubert, Rule 702 was amended to include the additional provisions which state that a witness may only testify 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.
Daubert motion should be filed within a reasonable time after th close of discovery. The hearing should be made well in advance of the first time a case appears on a trial calendar. Once certain evidence is excluded by a Daubert motion because it fails to meet the Daubert standard, it is unlikely that it will be used again in another trial. Even though a Daubert motion is not binding to other courts of law, if some evidence was found lacking, other judges usually follow that precedent.