the Frye test. The plaintiffs successfully argued that after Congress adopted the Federal Rules of Evidence in 1975, Frye was no longer the governing standard for admitting scientific evidence in trials held in federal court. The Supreme Court agreed and had already ruled that where common law rules conflicted with provisions of the Rules, the enactment of the Rules had the effect of supplanting the common law. Frye had remained part of the federal common law of evidence because it was decided almost 50 years before the Rules were enacted, but the text of the Rules did not suggest a congressional intent to keep the Frye rule, so the Court reasoned that Frye was no longer the rule. Rule 702 of the Federal Rules of Evidence provides (in part): If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise... The text of Rule 702 did not make admissibility of expert testimony depend on general acceptance, and there was no evidence that Congress intended to incorporate a general acceptance standard into Rule 702. "Given the Rules' permissive backdrop and their inclusion of a specific rule on expert testimony that does not mention 'general acceptance,' the assertion that the Rules somehow assimilated Frye is unconvincing. Frye made 'general acceptance' the exclusive test for admitting expert testimony. That austere standard, absent from, and incompatible with, the Federal Rules of Evidence, should not be applied in federal trials." The standard governing expert testimony Three key provisions of the Rules governed admission of expert testimony in court. First, scientific knowledge, meaning that the testimony must be scientific in nature and must be grounded in "knowledge." Since science cannot claim absolute certainty, instead representing "a process for proposing and refining theoretical explanations about the world that are subject to further testing and refinement," Rule 702 defines "scientific knowledge" as arising from the scientific method. Second, the scientific knowledge must assist the trier of fact in understanding the evidence or determining a fact in issue in the case. The trier of fact is often either a jury or a judge; but other fact finders may exist within the contemplation of the federal rules of evidence. To be helpful to