Legal Definitions - Daubert standard

The Daubert standard is a legal rule used by judges, primarily in federal courts and some state courts, to determine whether an expert witness's testimony is reliable and relevant enough to be presented to a jury. Essentially, it acts as a "gatekeeper" to prevent juries from hearing expert opinions that are based on unreliable science, unproven theories, or flawed methodologies.

This standard originated from the 1993 U.S. Supreme Court case Daubert v. Merrell Dow Pharmaceuticals Inc. It requires a trial judge to assess the underlying reasoning and methodology of an expert's testimony to ensure it is scientifically valid and can be properly applied to the specific facts of the case.

When evaluating expert testimony under the Daubert standard, judges typically consider several factors, though these are not exhaustive and can vary depending on the specific circumstances:

• Testability: Has the expert's theory or technique been tested, or can it be tested?
• Peer Review and Publication: Has the theory or technique been subjected to peer review and published in scientific journals? This suggests scrutiny by other experts in the field.
• Known or Potential Error Rate: What is the known or potential rate of error for the technique or theory?
• Existence and Maintenance of Standards: Are there established standards controlling the technique's operation?
• General Acceptance: Has the theory or technique gained widespread acceptance within the relevant scientific or technical community?

The Daubert standard applies not only to scientific experts but also to other technical or specialized experts, such as engineers or forensic specialists, ensuring that all expert opinions presented in court meet a threshold of reliability.

Examples of the Daubert Standard in Action:

• Product Liability Case with a Novel Medical Theory:

  Imagine a lawsuit where a plaintiff claims a new type of energy drink caused a rare neurological condition. The plaintiff's expert witness, a neuroscientist, proposes a brand-new theory about how certain ingredients in the drink interact with brain chemistry to cause the condition. This theory has not yet been published in peer-reviewed journals, nor has it undergone extensive independent testing.

  How Daubert applies: The defense would likely file a Daubert motion, asking the judge to exclude the neuroscientist's testimony. The judge would then evaluate the neuroscientist's theory based on the Daubert factors. If the judge finds that the theory lacks sufficient testing, peer review, or general acceptance within the neuroscience community, they might rule that the testimony is unreliable and cannot be presented to the jury, preventing the jury from being swayed by an unproven scientific claim.

• Construction Defect Case with an Unconventional Engineering Analysis:

  Consider a case involving a collapsing bridge, where the plaintiff's expert, a structural engineer, presents a unique computer modeling technique to demonstrate a design flaw. This modeling technique was developed solely by the expert's private firm, has not been validated by independent engineering bodies, and its error rate is unknown outside of the firm's internal assessments.

  How Daubert applies: The opposing party would challenge the admissibility of this expert's testimony. The judge would apply the Daubert standard to assess the reliability of the engineer's computer modeling technique. The judge would consider whether the technique has been tested, peer-reviewed by the broader engineering community, has a known error rate, and whether it's generally accepted as a valid method for structural analysis. If these criteria are not met, the judge might exclude the expert's testimony, ensuring that only reliable engineering analysis informs the jury.

• Criminal Case Involving Digital Forensics:

  In a criminal trial, the prosecution seeks to introduce testimony from a "digital evidence expert" who claims to have used a proprietary software tool to recover deleted data from a suspect's phone. The expert asserts that this tool can recover data that no other standard forensic software can, but the underlying algorithms of the software are a trade secret and have never been disclosed for independent verification or peer review.

  How Daubert applies: The defense would challenge this expert's testimony under the Daubert standard. The judge would scrutinize whether the proprietary software and the expert's methodology have been tested, subjected to peer review, have a known error rate, and are generally accepted within the digital forensics community. Without such validation, the judge would likely exclude the testimony, as the jury cannot properly evaluate the reliability of a secret, unverified technique, thus upholding the integrity of the evidence presented in court.