When Judges Play Scientist: Evidentiary Standards & Risks of Judicial Overreach
Scientific evidence is playing an increasingly important role in legal proceedings across the country. With the rise of new technologies, breakthroughs in science and medicine, and the threat of political tensions impacting the judiciary, determining the admissibility of scientific evidence has become an increasingly nuanced challenge. Who decides the types of evidence that may be introduced? Who is allowed to testify? What are they allowed to present? Who determines whether the evidence is reliable? On what grounds are those decisions based? And what happens when the science is controversial or untested?
Especially as issues related to physical healthcare, mental healthcare, and civil rights are on the docket in many states and federal courts across the country, the questions surrounding admissibility have become a crucial set of issues for lawyers, judges, and scientists alike—but more importantly, they are critical for the public whose rights and liberties are potentially at stake. Here, we delve into understanding the standards for scientific evidence in a legal setting and explore potential challenges of ensuring a fair outcome.
Numerous approaches have been proposed to determine the legal admissibility of scientific evidence and expert witness testimony on scientific issues, but two cases in particular—Frye v. United States, and Daubert v. Merrell Dow Pharmaceuticals—have had the greatest impact on establishing evidentiary standards for admitting scientific evidence, with each placing the decision-making power in different hands.
The Beginning of Scientific Evidence: Frye v. United States, 293 F. 1013 (D.C. Cir. 1923).
It's always more interesting to understand case holdings in terms of the people involved. In 1923, defendant James Frye had been convicted of second-degree murder. On appeal to the D.C. Circuit Court of Appeals, attorneys on behalf of Frye argued that the trial court had erred by refusing to allow into evidence the testimony of their expert witness; specifically, the defense had hoped to introduce evidence about a new systolic blood pressure deception-test, which the defense argued would show Frye was telling the truth about his innocence. The prosecution, however, objected to the admissibility of the test (and any expert witness testimony about it), arguing that it was not generally accepted by the scientific community as a reliable indicator of truthfulness. It was a winning argument.
The court ruled in favor of the prosecution, and in so doing, established the standard for admitting scientific evidence. Under the Frye standard, as it came to be known, admissibility of scientific evidence is based on whether a particular method, technique, or test is generally accepted as reliable in its particular scientific community. In Frye, the court ruled that the results of the deception test could not be admitted as evidence, as the scientific community had not yet widely accepted it.
Notably, in Frye, the court reasoned that the best “judges” of the evidence were experts on the topic, rather than the trial judges (who are instead experts in law). Decisions of admissibility would be based on the consensus of professionals in the field, providing a rational level of confidence in the trustworthiness of the science. If the science is accepted by experts in the field, the court will hear the evidence and decisions of credibility will be left to the jury, rather than to the gatekeeping of an arbiter.
A Change in Circumstances: Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).
Over time, the Frye standard came under criticism for being overly rigid, as it often excluded cutting-edge scientific methods that had not yet gained widespread acceptance. Nearly 70 years after the standard for admitting scientific evidence was established in Frye—and despite the apparent logic of the rule—the Frye standard was eventually replaced in federal (and some state) proceedings by new guidelines [1].
In 1993, the plaintiffs in Daubert v. Merrell Dow Pharmaceuticals, Inc. brought suit for damages against the defendant pharmaceutical company, alleging that birth defects to their children were caused by their mother using the defendant company’s anti-nausea drug Bendectin during pregnancy. Counsel on behalf of Daubert sought to introduce scientific studies and expert testimony to support their claim, but the trial court excluded the evidence, citing a lack of scientific reliability, and finding that it did not rise to meet the standard in Frye. As a result, summary judgment was granted in favor of Merrell Dow Pharmaceuticals. The Ninth Circuit Court of Appeals affirmed the lower court’s decision.
However, the Supreme Court vacated both of the lower courts’ rulings on the basis that Frye wasn’t even the appropriate standard in the first place. In its holding in Daubert, the Court ruled that the standards set forth in the Federal Rules of Evidence, rather than the Frye Standard, should be used to determine admissibility of testimony. In other words, the Court felt it should be up to the judge to determine whether the evidence is relevant and reliable, scientific or not—and nothing in the rules governing expert testimony required evidence to be “generally accepted” by anyone other than the judge.
The effect of Daubert was to take the job of assessing the reliability of scientific evidence out of the hands of the scientific community and place it squarely within the hands of the judge. That is a big ask.
There is also a question of qualifications.
In supplanting the Frye standard with the Daubert test, a concern may be raised over the number of hats that a judge is required to wear: first, as the trier of fact, and next not only as a gatekeeper for admissibility, but also as the determinant of scientific reliability—a task the judge may not be qualified or able to perform. While the Daubert ruling aimed to improve the reliability of expert testimony in federal court, it also created potential dangers and challenges for the admissibility of scientific evidence. Primarily, it stripped away some of the protections of non-partisan science and gave more power to the judge, who may or may not have the necessary expertise to evaluate the science effectively.
Almost as if they were aware of the potentialtfor Daubert’s application to devolve into a legal quagmire, the Court in Daubert created a set of guidelines to assist judges in in making a proper determination of admissibility. In particular, the judge must evaluate the testimony with regard to:
(1) whether the theory or technique is scientific knowledge that can or has been tested;
(2) whether the theory or technique has been subjected to peer review;
(3) whether there is a known or potential rate of error; and,
(4) whether the theory or technique is generally accepted in its field.
Although the fourth Daubert criterion echoes the Frye standard’s emphasis on general acceptance, the ultimate decision is still the province of the judge, and it is up to the judge to decide if the science is generally accepted in the field. One potential danger of the leeway offered to the courts by Daubert is that this subtle shift introduces a degree of subjectivity that could lead to inconsistencies across courts. It’s a step removed, a degree separated, in order to give the judge the final say. It’s not whether it’s accepted by experts, but whether the judge believes it is accepted by experts. This leaves a lot of room for interpretation, which could in turn create uncertainty and unpredictability in the legal system.
It’s a step removed, a degree separated, in order to give the judge the final say. It’s not whether it’s accepted by experts, but whether the judge believes it is accepted by experts. This leaves a lot of room for interpretation.
Another concern is that judges might—whether knowingly or unconsciously—use their “discretion” to exclude scientific evidence or testimony simply because it contradicts their personal beliefs or biases, even when that evidence is both relevant and reliable. This is an unsettling possibility.
While the ruling in Daubert may have aimed to create a more adaptable framework for the admissibility of scientific evidence, ironically its flexibility comes with inherent risks. Judges, who are trained in law rather than science, are now tasked with the formidable responsibility of assessing the reliability and relevance of scientific methods and findings—an expectation that may exceed their expertise. This added layer of interpretation distances the court from the scientific community, potentially introducing inconsistency and bias, which, in turn, could undermine public confidence in the legal system. Although the majority of judges who face these determinations will do so with sound reasoning and impartiality, the risk is enormous when lives and liberties may be on the line.
To address these challenges, it might be worthwhile to revisit the balance between Frye and Daubert. From a policy standpoint, a hybrid approach that balances the objectivity of the Frye standard with the flexibility of Daubert may provide a more effective solution. For instance, courts could defer to the consensus of scientific experts, as in Frye, while also allowing judges the flexibility to admit novel evidence under Daubert, provided that such evidence is subject to peer review or corroboration by neutral, court-appointed experts. Additionally, comprehensive judicial training in scientific reasoning and evaluation could help ensure that judges are better equipped to assess the reliability of complex evidence. Such measures would not only promote fairness but also safeguard against the misuse or misunderstanding of scientific evidence.
Ultimately, the goal of any evidentiary standard should be to uphold the integrity of the judicial process by ensuring that scientific evidence is evaluated accurately and applied equitably. The consequences of evidentiary decisions ripple beyond courtrooms, impacting individuals’ rights, access to justice, and public trust in the system. As science and technology continue to evolve, so too must our legal standards—balancing flexibility with rigor to protect the rights and liberties of all parties. By revisiting, understanding, and perhaps refining the guidelines established for scientific evidence, the legal system can create a more consistent, transparent, and just framework for incorporating scientific evidence into court proceedings.
Sarah Elizabeth Wellard
[1] These criteria have since been integrated into the latest version of the Federal Rules of Evidence (Rule 703), governing all United States Federal Court proceedings. The Court extended this finding in Kumho Tire Co. v. Carmichael (526 U.S. 237, 1999), ruling that the Daubert standard applies to all types of expert testimony, whether or not it is presented by scientists.
Notably, although the Federal Rules of Evidence (governing all Federal legal proceedings) are in line with the Daubert standard, many states, (including Illinois) have declined to follow Daubert in cases with local or state jurisdiction, and instead have continued to employ the Frye standard today. In Illinois and others, this means that admissibility is based on whether experts in the field respect the science.