The Federal Rules of Evidence were adopted by order of the Supreme Court on November 20, 1972, transmitted to Congress by the Chief Justice on February 5, 1973, and came into effect on July 1, 1973. L. 93-12, 30 March 1973, 87 Stat. 9, provided that the proposed rules «shall have force and effect only to the extent and with the amendments expressly authorized by the law of Congress». L. 93-595, January 2, 1975, 88 Stat. 1926, promulgated the Federal Rules of Evidence proposed by the Supreme Court, with amendments in Congress that were to take effect on July 1, 1975. In 1975, Congress passed new federal rules of evidence. Federal Rule 702 treats and controls testimony in all federal courts, and many state courts have adopted it in substance. The rule states: Therefore, practitioners and experts must be aware, when faced with a Daubert challenge to expert testimony, that it is the role of the trial court – that is, the trial judge – to serve as a gatekeeper to ensure that only relevant and reliable expert opinions reach the jury.
The judge will not demand perfection, but the expert must prove that he or she has «applied in the courtroom the same level of intellectual rigour that characterizes an expert`s practice in the field in question.» 13 In Daubert, the Court, which ultimately considered whether the use of a prescription anti-nausea drug during pregnancy had caused congenital malformations in children, held that the judges of the Federal Court should play the role of guardians of the admissibility of scientific evidence. The Court stated that «the trial judge must ensure that any admissible testimony or scientific evidence is not only relevant, but reliable.» The reliability or «reliability» of scientific evidence, the court continued, should be based on «scientific validity.» The Court did not provide an exhaustive list of factors that a trial judge must consider in making such a decision, but it did identify some relevant considerations. The question is whether a theory or technique used by an expert «can (and has been) tested, whether it has been «peer-reviewed and published», whether there is a «known or potential margin of error» in the methodology, and whether there are «standards that control the operation of the technique». The Court added that the concept of `general acceptance` remains a relevant consideration. The inquiry, the court said, should be «flexible,» although «of course, the focus should be solely on the principles and methods, not the conclusions they generate.» In ruling on Daubert, the court clarified that its decision was limited to the «scientific context» of the case and left the question of standards applicable to «technical or otherwise specialized knowledge» to another day. This was an important limitation, as the testimony of experts in science represents only a small part of the expert testimony presented to the court. A 1998 study of civil cases in federal courts with expert testimony indicates that only 7.3 per cent of experts testified on the basis of a scientific field. 38 According to the federal rules of evidence, hearsay evidence is «testimony that is not given by the person who testifies at trial or hearing and that is presented as evidence to prove the truth of the alleged case.» Rule 703 is another important rule for expert witnesses and the opinions they can express in their testimony. This rule states: With respect to medical expert testimony specifically, the Court of Appeals for the Eighth Circuit has established the following admission standards: Although not required by the Federal Rules of Evidence, in practice the judges have concluded that the testimony of medical experts, particularly expert opinions regarding brain injury or injury, because of its very persuasive – or perhaps negative – impact on a jury.15 In addition, federal judges are often seen as gatekeepers and deny the admissibility of expert testimony more often than in state courts.