Understanding the Admissibility of Scientific Evidence in Court

Have you ever heard of the “Daubert/Frye” test? The apparent merging of the Frye and Daubert standards reflects a certain confusion that exists on the appropriate legal standard for the admissibility of scientific evidence, particularly in criminal cases. While the standard for the admission of scientific evidence can vary widely from federal courts to state courts and from state to state, every jurisdiction in the United States relies on either the Frye or the Daubert standard.^[1] No jurisdiction has a Daubert/Frye standard.

Frye v. United States

The Frye standard is named after the case of Frye v. United States.^[2]  In Frye, the D.C. Appellate Court considered an appeal from a defendant convicted of second-degree murder. The appeal was made on the sole grounds that the trial court erred when it did not allow an expert witness to testify about the result of a systolic blood pressure deception (polygraph) test. The lower court refused to admit the result of the polygraph test as it did not have significant general acceptance in the scientific community. In upholding the trial court, the three judge panel ruled that polygraph testing had not gained enough “standing and scientific recognition among physiological and psychological authorities” to justify its admission as evidence in courts of law. This short 641 word opinion, became “a landmark in the law of evidence and one of the most cited cases in the history of American law.”^[3] By 1979, the Kansas Supreme Court wrote that the Frye test was the scientific evidentiary standard in almost all of the courts in the United States.

The Frye test is fairly straightforward, as described in the Science Bench Book for Judges, the proponent of novel scientific evidence was required to show general acceptance in the relevant scientific community (and also, as with any evidence, relevance, proper foundation, and that the novel scientific evidence was not otherwise excluded from evidence). If a judge determines that there is general acceptance, the evidence is to be admitted.

Daubert v. Merrell Dow

 The Frye Standard wasn’t meaningfully challenged until 1993 in the case of Daubert v. Merrell Dow Pharmaceutical.^[4]In Daubert, the United States Supreme Court held Frye had been supplanted by Rule 702 of the Federal Rules of Evidence: 

“If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.”^[5]

Federal Rules of Evidence 702

The court then set forth what it termed non-exclusive factors to determine the admissibility of expert evidence. These factors included: whether the theory or technique used by the expert has been tested, whether the theory or technique has been subject to peer review, the potential rate of error associated with the theory or technique, and whether the theory or technique is generally accepted within the relevant scientific community. So, under Daubert, the court was required to evaluate the scientific evidence itself.

Another key difference between the two standards arises over the question of admissibility. Frye only applies when the evidence is based on new scientific principles or techniques. If the scientific evidence is based on well-established principles or techniques the court simply admits it. Daubert, on the other hand, requires that the judge become the gatekeeper for the admission of scientific evidence each and every time.

Many state jurisdictions have shifted to the Daubert Standard. This shift appears to have occurred due to Daubert’sallowance of a broader range of admissibility for scientific evidence. Recently, however, the Daubert Standard has come under attack on the grounds that it is too subjective, causing inconsistent appellate rulings. This has caused some scholars to argue for the creation of a new standard.

Scientific Evidence Must be Reliable and Trustworthy

Whatever standard is applied the goal must be the same, ensuring that scientific evidence offered into evidence is reliable and trustworthy. This is all the more important as there have been concerns raised about the lack of consistency in the admission of scientific evidence, between civil and criminal cases. Also, experts have criticized certain types of forensic evidence, such as bite mark analysis and hair analysis, which they claim are not based on reliable scientific principles, should not be admitted in court. These concerns have led to calls for greater scrutiny of scientific evidence in the way that scientific evidence is evaluated in the courts.

In order to address these concerns, both the Daubert and Frye standards must be applied in such a way as to ensure that the admission of scientific evidence is reliable and trustworthy. While there is no Daubert/Frye test, each individual standard must be applied in a way that leads to just and fair decisions and outcomes.

---

^[1] For in-depth discussions on the admissibility of scientific evidence and the two legal standards, read more in the Justice Speakers Institute’s Science Bench Book for Judges, 2d ed. 

^[2] 293 Fed. 1013 (D.C. Cir. 1923)

^[3] Justice Speakers Institute, Science Bench Book for Judges, pg. 223.

^[4] 509 U.S. 579 (1993) 

^[5] Id.