Legal Definitions - Daubert hearing

A Daubert hearing is a special proceeding conducted in federal courts, typically before a trial begins. Its primary purpose is for a judge to evaluate whether the scientific, technical, or other specialized expert testimony that a party wants to present to a jury is both relevant to the case and sufficiently reliable. This standard for admitting expert testimony was established by the U.S. Supreme Court in the landmark 1993 case of Daubert v. Merrell Dow Pharmaceuticals.

During a Daubert hearing, the judge acts as a "gatekeeper," scrutinizing the expert's qualifications, methodology, and conclusions. The judge considers factors such as whether the expert's theory or technique has been tested, subjected to peer review and publication, has a known or potential error rate, and is generally accepted within the relevant scientific community. This process ensures that only credible and sound expert evidence reaches the jury, preventing speculative or unproven theories from influencing the outcome of a trial.

Here are some examples of when a Daubert hearing might occur:

• Example 1: Product Liability Lawsuit

  Imagine a lawsuit where consumers claim that a new dietary supplement caused liver damage. The plaintiffs' legal team wants to introduce testimony from a biochemist who asserts that a specific ingredient in the supplement, based on a novel hypothesis, directly leads to liver toxicity. The supplement manufacturer's lawyers would likely request a Daubert hearing. The judge would then examine the biochemist's research methods, the scientific basis of their hypothesis, and whether their theory has been peer-reviewed or widely accepted in the scientific community. If the judge finds the biochemist's methodology too speculative or lacking sufficient scientific rigor, their testimony would be excluded from the trial.

• Example 2: Environmental Contamination Case

  Consider a case where a town is suing a chemical plant, alleging that the plant's historical waste disposal practices contaminated the local groundwater, leading to health problems among residents. The town's expert witness, a hydrologist, plans to present a complex computer model predicting the movement of contaminants through the soil and water over several decades. The chemical plant's defense team would likely challenge this expert's testimony through a Daubert hearing. The judge would scrutinize the computer model's underlying data, the assumptions it makes, and whether the model itself has been validated or is generally accepted as a reliable tool for predicting long-term contaminant spread. If the model is deemed unproven or its scientific basis questionable, the judge might prevent the hydrologist from presenting it as expert evidence to the jury.

• Example 3: Forensic Evidence in a Criminal Trial

  In a criminal case, the prosecution intends to present testimony from a forensic expert who used a relatively new and unstandardized technique to analyze a unique pattern found in tool marks at a crime scene. This technique is not yet part of established forensic databases or widely accepted protocols. The defense would likely request a Daubert hearing to challenge this expert testimony. The judge would evaluate whether the new forensic technique has been adequately tested, whether its error rate is known, if it has been subjected to peer review, and if it is generally accepted within the forensic science community. If the judge concludes the technique lacks sufficient scientific rigor or reliability, the expert's testimony regarding the tool mark analysis might be disallowed, preventing potentially unreliable evidence from influencing the jury's decision.