Also known as: reliable principle and method · FRE 702 · Daubert reliability
Written by attorneys · grounded in primary & secondary sources — see below
A criterion for the admissibility of expert opinion testimony under Federal Rule of Evidence 702 requiring that the opinion rest on trustworthy principles and methods rather than speculation or untested techniques. The trial court acts as gatekeeper and must find by a preponderance of the evidence that the methodology itself is reliable before the testimony reaches the jury.
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In Carla Nguyen's malpractice suit against Riverside Medical Center, the hospital offers defense expert Dr. Elena Lopez. Dr. Lopez bases her standard-of-care and causation opinions entirely on a proprietary in-house cancer risk-scoring model she helped design that has never been independently validated or peer reviewed. The plaintiff objects. The court must decide whether the model itself satisfies the reliability requirement before allowing the testimony.
Pacific Logic sues United Cloud for patent infringement on a facial recognition algorithm. United Cloud offers computer scientist Owen who relies on a self-developed benchmarking script and unreviewed internal test results to claim non-infringement. Owen also extrapolates from informal laptop tests to assert industry-leading accuracy. Pacific Logic moves to exclude the testimony. The court must determine whether the script and extrapolation rest on reliable principles and methods.
The court must scrutinize the methodology itself rather than merely the expert's credentials. It asks whether the principles and methods are grounded in sound discipline, have been tested, subjected to peer review, possess a known error rate, and are reasonably used in the field. A proprietary unvalidated model or self-developed unreviewed script raises this threshold inquiry directly.
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The requirement applies to all expert testimony based on technical or other specialized knowledge. Courts take a flexible case-specific approach and may consider the traditional Daubert factors or any other appropriate indicia of reliability suited to engineering, computer science, or other non-scientific fields.
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The absence of testing, peer review, or documented error rates weighs heavily against admissibility. The court may still conclude the methods are reliable if other indicia of trustworthiness exist, but the proponent must carry the burden of showing reliability by a preponderance of the evidence.
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Reliable principles and methods focus on the methodology in the abstract. Reliable application focuses on whether the expert actually used those methods correctly on the specific facts without creating an impermissible analytical gap between data and opinion.
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