Expert Witness

An expert witness in a personal injury claim is someone whose extensive knowledge and/or experience in a certain field allows them to give a professional opinion on matters that are under dispute. An expert witness can be a crash expert who helps prove how a car accident occurred, an engineer testifying about design defects in a product liability claim, a physician attesting to the standard of care in a medical malpractice claim and more.

An expert witness differs from a lay witness, such as an eyewitness to an auto accident, who can only testify to what can be rationally gleaned from their perception or firsthand knowledge, and in what helps clarify matters for a trier of fact, and who cannot testify to scientific, technical or specialized knowledge. The purpose of an expert witness is to objectively offer information and expert opinion on facts that need technical explanation. They can be used in a trial or in litigation.

Courts have to determine who qualifies as an expert witness and what testimony they are allowed to attest to. Over time, the standards in Federal courts and in individual states have changed. There are currently two standards used for admitting expert witness testimony: the “Frye” standard and the “Daubert” standard.

The “Frye” Standard for Expert Witnesses

In 1923, in Frye v. United States, the D.C. Court of Appeals took on the appeal of a murder conviction on around the admissibility of what was essentially an early version of a lie detector test. Under the Frye standard, expert testimony may be admitted if it is: sufficiently established to have gained general acceptance in the particular field in which it belongs.

The results were deemed inadmissible as the systolic blood pressure deception test used to get them had not gained general acceptance in its field.

The Frye standard was adopted by Federal courts and many states. Today, Illinois still uses the Frye standard for admitting expert testimony in jury trials.

The “Daubert” Standard for Expert Witnesses

Federal courts and Missouri currently use the “Daubert” standard for admission of expert testimony. In Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), the Supreme Court of the United States ruled that Federal Rule of Evidence 702, which was enacted in 1975, superseded the previous Frye standard. Under Rule 702, a witness may qualify as an expert if:

1. the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;
2. the testimony is based on sufficient facts or data;
3. the testimony is the product of reliable principles and methods; and
4. the expert has reliably applied the principles and methods to the facts of the case.

Daubert loosens the admissibility standard a bit, as under the standard expert testimony is allowed if the judge deems it reliable, even if it has not gained general acceptance in the relevant field.

In 2017, Missouri Governor Greitens signed House Bill No. 153 into law, which changed the standard in Missouri from Frye to Daubert by having Missouri Revised Statute §490.065 adopt Rule 702’s language verbatim.