Also known as: active gatekeeper · gatekeepers
Written by attorneys · grounded in primary & secondary sources — see below
Federal district courts acting under Federal Rule of Evidence 702 as active gatekeepers that must screen proffered expert testimony for both relevance and reliability before permitting it to reach the jury. Reliability is evaluated through a flexible, case-specific inquiry that may consider factors such as testing, peer review, error rate, controlling standards, and general acceptance. The court must determine for itself that the expert's principles and methods are reasoned and objective rather than speculative or subjective.
Select any source to read its text and confirm it supports the definition.
Aisha Ahmed, representative of a deceased pilot's estate, sued Artemis Logistics after a plane crash. Artemis offered an aerospace engineer whose proprietary fluid-dynamics model had been tested only internally and never validated against actual crash data. The district court conducted a Daubert hearing, applied the reliability factors itself, and excluded the testimony because no known error rate existed for real-world application.
Antonio Alvarado's company sued Atlas Ventures alleging a drug caused heart failure. Atlas offered a biostatistician who performed a novel, post-hoc subgroup analysis never pre-specified in the trial protocol and never peer-reviewed in cardiovascular literature. The court, acting as active gatekeeper, excluded the testimony after finding multiple Daubert factors unsatisfied despite the underlying data coming from FDA protocols.
Amelia Amari's firm sued Astra Aerospace for patent infringement. Astra offered a computer scientist whose self-developed benchmarking script had never been tested outside the company or subjected to peer review. The district court held a hearing, determined the principles and application were unreliable, and excluded the testimony to fulfill its gatekeeping duty.
Arthur Abrams sued Avalon Pharmaceuticals claiming injury from a medication. Avalon offered an expert whose conclusions rested on unreviewed internal test results and informal laptop runs with no documented error rate. The court excluded the testimony after concluding the methodology failed the reliability threshold the judge was required to assess independently.
Federal judges must determine for themselves that an expert's principles and methods are reliable rather than deferring to general acceptance in the field. They evaluate factors such as testing, peer review, error rate, and standards controlling the technique. This independent assessment prevents speculative or subjective testimony from reaching the jury.
Supporting sources
No single Daubert factor is dispositive. A court may still admit testimony when other indicia of reliability are present, such as testing on similar datasets or derivation from established techniques. The inquiry remains flexible and case-specific.
…claimed would not be readily containable by reference to facts about the mind that are matters of difficult judgment, or by gatekeepers who are subject to temptation, noble or not. Respondents propose an answer to all this, the answer of state regulation with teeth. Legislation proposed in several States, for example,…
…and floaters from voting”); see also Brief for Historians and Other Scholars as Amici Curiae 4–15 (detailing abuses); R. Hayduk, Gatekeepers
…correctly a recurring issue of state law—transcend the interests of individual litigants, rendering it imprudent to cast them as gatekeepers
Supporting sources
The reliability inquiry extends to all expert testimony based on technical or specialized knowledge. Courts may consider the Daubert factors or other appropriate markers tailored to the field, such as industry benchmarking standards.
Supporting sources
The admission or exclusion of expert testimony is reviewed for abuse of discretion on appeal. A court that admits testimony without assessing reliability or excludes it without a reasoned application of the factors risks reversal if the decision falls outside the range of permissible discretion.
Supporting sources