The Honorable André M. Peñalver is a Superior Court Judge in Pierce County, where he has served since July 2021. Judge Peñalver was born and raised in the Tacoma area. He received his bachelor’s degree from Harvard and his law degree from Cornell. He practiced civil litigation at Gordon Thomas Honeywell in Tacoma and Stokes Lawrence in Yakima, Washington, where he practiced in state and federal courts. He left private practice to serve as an Assistant United States Attorney in the General Crimes Unit of the Tacoma branch office until his appointment to the bench.
ADVERSARIES AND EXPERTS
I. Introduction
The motion before the Court was routine. In a personal injury case, the defense moved under Civil Rule 35 to compel a neuropsychological examination. The plaintiff alleged psychological harm. The defense retained a neuropsychologist who proposed a standard battery of tests, with one condition: the testing portion could not be observed.
The objection was equally familiar. Plaintiff’s counsel argued that a CR 35 exam is an adversarial proceeding, and that fairness required observation by counsel. Washington case law supported that position. The legal arguments were sound.
But so was the science.
The neuropsychologist submitted peer-reviewed literature explaining that third-party observation measurably compromises the testing. Even small deviations from standardized conditions risked invalidation.
The courtroom became a place of failed translation. One side spoke the language of adversarial rights. The other spoke the language of empirical validity. Each was internally coherent. Each was correct within its own discipline. And yet the Court had to choose.
The solution—ordering the examination with a hidden camera unknown to the examinee—was pragmatic. It also revealed something deeper: when courts confront scientific disciplines, our legal system lacks the tools to reconcile adversarial fairness with empirical truth. Judges improvise. Lawyers argue past one another. And courts resolves epistemological conflicts with procedural compromises rather than principled frameworks.
As trial lawyers know well, these conflicts are not rare. They are now routine.
II. Adversaries vs. Experts: Law vs. Science
In a recent article in Seattle University Law Review Online, Adversaries and Experts,[i] I explore this tension and its historical roots. The article explores why law and science so often talk past one another, how Western medicine adapted to empirical reasoning while Western law largely did not, and what modest, practical steps might help lawyers and judges better navigate scientifically grounded disputes, without abandoning the adversarial system that remains central to our profession.
At the heart of this tension are two very different ways of deciding what counts as true. The adversarial legal system, with its roots in medieval dialectics, assumes that truth emerges from structured argument, precedent, and procedural fairness. Empirical sciences—whether in medicine, psychology, engineering or other forensic fields—operate on a different epistemology: truth depends on data, replication, and error rates.
As scientific disciplines increasingly shape litigation, this mismatch creates predictable problems. Courts rely on experts yet lack the training to evaluate scientific reliability. Evidence rules designed to protect adversarial fairness can exclude reliable data. Consider for a moment how the Hearsay Rule treats an article from the National Institute of Health with the same skepticism as a barroom rumor—unless a lawyer can afford the right expert to sponsor it. Operating under such rules, lawyers may win arguments that are doctrinally sound but empirically unsupported.
Drawing lessons from medicine’s evolution, the article proposes incremental reforms: greater empirical literacy in law, more flexible evidence rules, and clearer expectations on data.
The aim is not to diminish the adversarial system, but to strengthen it—by ensuring that when science enters the courtroom, we have the right tools to address it.
III. What to do while we wait
While the law grows toward empiricism—a tall order—there is much we can still do to make the best use of empirical facts in any particular case.
1. Treat Scientific Claims Seriously
When a case turns on data, persuasion alone should not be enough. Ask whether the claim is empirically supported, how it was tested, and what its limitations are. You do not need to become a statistician, but basic competence in study design, error rates, and reliability will make you a better trial lawyer. (Accessible introductions include The Art of Statistics or even Statistics for Dummies.)
Experts should illuminate science, not replace a lawyer’s understanding of it. Nobody expects a physician to consult an expert every time she evaluates data; the reason, of course, is that the physician is the expert. But doctors did not become so by accident. Developing competence in empirical reasoning was a conscious choice by the medical profession.
Lawyers can make the same choice. The old quip, “I went to law school to avoid doing math,” has long lost its humor. A lawyer who can independently assess an expert’s methodology is better positioned to present credible testimony and to expose flawed opinions. And if the lawyer does not understand the science, it is a safe bet that neither will the judge.
Strong advocacy begins with understanding the science. Stronger advocacy means taking it seriously. Do not search for data to bolster an argument; craft the argument from the data itself. It will produce advocacy that withstands both a competing expert and a judge who is paying attention.
2. Frame Empirical Issues Explicitly for the Court
Judges often decide between doctrinal arguments and scientific ones without a clear framework. Law schools need to catch up to training competence in data, much as medical schools did a century ago. In the meantime, help the court by explaining why empirical validity matters in a particular context and what happens when scientific standards are compromised.
3. Think Creatively About Procedural Solutions
In discovery disputes, evidentiary hearings, and motions practice, consider whether proposed safeguards enhance or undermine the science. Procedural fairness and empirical rigor need not be mutually exclusive, but courts often need help seeing how to protect both. Some creativity may be necessary to jerry-rig a bridge from medieval legal principles to modern empirical data.
IV. Conclusion
Anglo-American law has not undergone the same reckoning with empirical reality that medicine underwent. While such reform awaits, the law may need more humility when it interacts with sciences, more discretion to incorporate science into our process, and some reexamination of our medieval roots. When one compares the miracles of modern medicine with the horrors of its recent past, it is astonishing to think what we in the legal profession have yet to achieve.
[i] "Adversaries and Experts: Legal Tradition Versus Empirical Science" (2026). Seattle University Law Review Online. 39, https://digitalcommons.law.seattleu.edu/sulr_supra/39.
