The Perils of Junk Science in the Courtroom

R Street has been researching the issue of legal system abuse for several years. In particular, we have been analyzing the drivers of unmerited, or frivolous litigation that leads to large courtroom awards. Our deep dive has explored drivers including attorney advertising, third-party litigation funding, phantom damages, insurance fraud, and plaintiff bar applied human psychology. In this piece we turn attention to yet another driver of lawsuit system abuse—the phenomenon of expert witnesses who are not experts—called junk science.

Lawsuits alleging medical malpractice require plaintiffs to demonstrate that the offending physician violated a “standard of care,” which is what a reasonable physician would do in a given circumstance. Similarly, lawsuits involving product liability require plaintiffs to show that the defendant’s product had errors in design or manufacturing, or did not warn consumers of potential side effects. Because both types of lawsuits involve technical medical and product engineering expertise, both plaintiff and defense counsel may engage expert witnesses to explain to the judge and jury why their positions are justified. And because expert witnesses may be hired guns, especially on the plaintiff side, it is important that expert witnesses be objective and focus their remarks on their expertise. When there is a low bar for expert witnesses and their testimony to be allowed, frivolous, unmerited lawsuits may enter the courtroom. This can lead to courts delivering large awards, out of proportion to the merits of the case. Such jumbo awards drive up the cost of liability insurance, contributing to an inflationary “tort tax.”

What Is Junk Science?

“Junk science” refers to flawed expert witness testimony masquerading as sound science. Driven by spurious, faulty, or fraudulent research, data, argumentation, or technical analysis, junk science lacks rigorous methodology, peer review, or empirical evidence. Expert witnesses who traffic in junk science can easily mislead courts, policymakers, and the public.

The term “junk science” first attained currency in Galileo’s Revenge: Junk Science in the Courtroom, in which author Peter Huber critiqued the use of unreliable science by expert witnesses in U.S. courtrooms. He cited numerous examples, including the case of a plaintiff who claimed to lose their psychic abilities following a CAT scan. A year later, the 1992 Republican Party platform declared the party’s opposition to junk science, stating, “We will throw out ‘junk science’ by requiring courts to verify the legitimacy of persons called as expert witnesses. To restore integrity to courtroom testimony, we will ban the practice of paying fees to experts only if a successful verdict is obtained.”

Prior to 1993, the bar for having one’s day in court was relatively low. The prevailing standard expert witnesses had to meet to present testimony was the Frye Standard, which focused on the general acceptance of scientific evidence as laid out in 1923’s Frye v. United States. The burden of proof evolved from the requirement for plaintiff attorneys to present an argument demonstrating that an injury is “possibly” caused by the defendant, to one that is “plausibly” caused by defendant, to “probably” caused by defendant. Thus we saw a successively stricter set of requirements for expert witnesses — the 1993 Daubert Standard, named after Daubert v. Merrell Dow Pharmaceuticals — came in 1993. While some state courts still use Frye, federal courts regularly use Daubert. Subsequent amendments to Federal Rule of Evidence 702 further strengthened the criteria for expert witness admissibility.

The progression from Frye to Daubert and to Rule 702 as modified represents a tightening of the pleading standard — the minimum level of detail and factual support for a plaintiff to state their claim and survive a motion to dismiss. This trajectory is important because the stronger the pleading standard, the less likely frivolous, unmeritorious claims enter the courtroom and distort the market with outsized awards, ultimately paid by insurance markets.

What Is Federal Rule of Evidence 702?

The Federal Rules of Evidence guide the admission or exclusion of evidence in federal court proceedings. In 2000, the Judicial Conference of the United States (with approval from the Supreme Court and Congress) amended Federal Rule of Evidence 702, which requires expert witnesses to meet all four of the following standards in order for their testimony to be admissible:

(a) [Th]e 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;

(b) [T]he testimony is based on sufficient facts or data;

(c) [T]he testimony is the product of reliable principles and methods; and

(d) [T]he expert has reliably applied expert’s opinion [and] reflects a reliable application of the principles and methods to the facts of the case.

The 2023 amendment introduced a slight clarification of subpart (d), which now reads:

• [T]he expert’s opinion reflects a reliable application of the principles and methods to the facts of the case.

While the change appears minor, it has generated a torrent of law review articles, webinars and U.S. Court Committee and Judicial Conference notes. It has also inspired consumer advocacy organizations and the defense bar to promulgate their own positions. At a high level, citizen groups maintain that the amendment to Rule 702 will restrict citizens’ access to the courts and to justice. Groups aligned with the defense bar largely welcome the revision.

Another clarification to the rule is that the weight of expert testimony must be judged as “more likely than not” rather than based on “a preponderance of the evidence.” This is a fine distinction, but many in the legal community — especially those aligned with the plaintiff bar — find that the change favors defense arguments and could result in more rejection of expert witness testimony than would otherwise be the case.

What’s the Fuss About?

Literature review and discussions with subject matter experts from the plaintiff and defense bars reveal that many courts are not applying Rule 702 correctly. A 2015 Law Review article showed that some courts had not been applying Rule 702 as intended, or even as written. Instead, many courts emphasized a “liberal” policy favoring the admission of expert testimony and deferred questions on the reliability of scientific evidence to juries. A 1998 article in the Fordham Urban Law Journal came to a more cynical conclusion: “[J]unk science in the courtroom emanates from testimony by expert witnesses hired not for their scientific expertise, but for their willingness, for a price, to say whatever is needed to make the client’s case.”

Passing as an expert witness in court has been easy in many states for many years. For example, in Commonwealth v. Kilgore, Pennsylvania held that “[t]o qualify as an expert witness, a witness need only have a ‘reasonable pretention to specialized knowledge’.” A very low bar indeed. Expert witnesses’ work can be remunerative — according to Physicians Weekly, four hours of expert testimony per week could generate over $100,000 in income.

Addressing the prevailing liberal standard allowing expert witnesses, Daubert affirmed in 1993 that trial judges act as “gatekeepers” to ensure expert testimony is reliable and relevant. The responsibility is theirs because jurors lack sufficient scientific knowledge in healthcare, product manufacturing, and other highly technical fields. Daubert held that expert testimony must be rooted in sound reasoning and appropriate methodology rather than an impressive resume and qualifications, in fields that may be directly connected to the allegations. Even after its introduction, not all courts were applying the Daubert criteria regarding expert witness testimony. This is what led federal lawmakers to clarify Rule 702 via amendments to the Daubert Standard in 2000 and again in 2023.

The 2023 revision was driven by the observation that important federal circuit court cases interpreted Rule 702 in a manner inconsistent with the rule as written. A 2024 article in Texas A&M Law Review concluded that decisions by federal courts incorrectly applying the reliability requirements set forth in Rule 702 necessitated the latest amendment. Similarly, a 2006 article in Hofstra Law Review found that defense bars were not applying the rule as intended in many courts. The plaintiff side’s main concern is that the new, more stringent rule will cause many cases to be overturned.

Who Is Arguing?

Unsurprisingly, organizations aligned with the plaintiff bar largely oppose the clarification while those associated with the defense bar support it.

A June 2022 report from the Committee on Rules of Practice and Procedure features hundreds of public comments and hearing testimony summaries regarding the clarification of Rule 702 — including one from a plaintiff attorney association that opposes the clarification because it makes it harder for expert witnesses to satisfy all four criteria. Of 20 such summaries, only six oppose the clarification while 14 support it.

What Does the Future Hold?

It is too early to determine whether the 2023 clarification is having an impact in civil litigation that is reflected in insurance results. Changes to the pleading standard, from possible, to plausible to probable, have raised the bar for admissibility, and the implementation of stronger Rule 702 criteria is a promising step toward preventing testimony from witnesses whose motives are personal rather than professional. As argued in the 2006 Hofstra article, “There is no more important issue in the law of torts than factual causation. If a defendant is held liable for something it did not do, then the justice system has failed.” Coupled with numerous efforts to clarify expert witness requirements, this statement has implications for liability insurance business products (e.g., commercial general liability, bad faith, personal and commercial automobile liability, medical professional liability, directors and officers’ liability). If applied correctly, the new pleading standard will play an important role in keeping frivolous litigation out of the courtroom.