Litigation attorneys, corporate legal departments managing technical disputes, and insurance cover and claims counsel should read this article to learn more about:
Learn how highly technical experts can improve juror comprehension without weakening scientific rigor.
Understand why transparent reasoning and acknowledgment of uncertainty enhance witness credibility.
Gain insight into communication techniques that help juries understand causation, exposure, risk, and engineering failures.
Recognize the value of multidisciplinary experts who connect science, regulation, and litigation strategy.
Better evaluate and prepare expert witnesses for deposition, trial, arbitration, and mediation.
John draws on more than 30 years as an environmental attorney and expert witness to examine how specialists across scientific disciplines translate complex evidence for juries. Through these cross-disciplinary conversations, John highlights the shared practices that make technical testimony clear, credible, and respectful.
Executive Summary
One of the most important, and often overlooked, aspects of expert witness testimony is translating highly technical science into language that jurors can understand without sacrificing accuracy or respect. Drawing on insights from five senior J.S. Held experts in epidemiology, toxicology, human factors, meteorology, and geotechnical engineering, this article demonstrates that successful testimony is not about reducing science to slogans but about teaching complex concepts in a way that enables jurors to follow the evidence independently and reach informed conclusions.
Introduction
I have spent a lot of years around expert witnesses, and I have watched the same thing happen more times than I can count. You put a brilliant scientist on the stand, someone who is genuinely at the top of their field and completely right about the science, and within a few minutes, you can feel the jury drifting away. The science is almost never the problem. The problem is the gap between the way an expert thinks and the way 12 people pulled out of their ordinary lives actually take in, hold on to, and come to trust what they are being told. Closing that gap is the real work, and it is a good deal harder than it looks.
At J.S. Held, we live with this every day. Our people testify in epidemiology, toxicology, industrial hygiene, human factors, meteorology, geotechnical engineering, and a long list of other disciplines, and they have done it in state and federal courtrooms, in arbitrations, in the occasional hot-tub panel where the experts are questioned side by side, which was an interesting experience the time it happened to me, and in front of judges and opposing counsel who were plenty sharp. What all of that has taught us is that persuading a jury with difficult material is a craft. It can be taught, practiced, and get better with both. It has also taught us that the way an expert most often loses a jury is not by oversimplifying. It is by talking down to them.
The goal is not to make the jury feel smart. It is to make them feel respected, and then to give them what they need to reach the right conclusion on their own.
There is a real difference between simplifying something and dumbing it down, and a jury feels that difference long before they could put a name to it. When I simplify, I am doing the work of finding the clearest path to an idea so that the person listening does not have to hack through the underbrush to reach it. That is a form of respect. Dumbing down is the opposite. It hides the reasoning, hands over a conclusion, and asks the jury to take it on faith because someone with a title said so. The expert who leans on their credentials and says, "Trust me, I have a PhD," has already lost the room. The one who says, "Let me show you how I know this," and then actually walks them through it still has a chance to win it.
What surprises people is that the deepest experts are usually the best at this, not the worst. Real mastery of a subject is exactly what lets someone strip an idea down to what matters without bending it out of shape. Shallow knowledge is what hides behind jargon. Deep knowledge can afford to speak plainly. So, we start with genuine technical depth, and only then do we worry about how to communicate it.
On the following pages, five of our senior experts discuss the hardest part of translating their own field for a jury. The question underneath all of it is a simple one. How do you take something genuinely complicated and put it in front of twelve people in a way that actually helps them decide?
The Epidemiologist: Making Populations Personal
Allison Stock, PhD, MPH, MS
Toxicology/Epidemiology: 25 + years, CDC Epidemic Intelligence Service | Chief Scientist, EH&S
Epidemiology is the study of what happens to groups of people, and that is exactly what makes it so hard to put in front of a jury that has to decide about one person sitting in one chair. Allison spent years at the Centers for Disease Control and Prevention working outbreaks and exposures of every kind, from Legionella and post-Katrina formaldehyde to anthrax and SARS, and she states the core problem plainly. After that, she was the Senior Epidemiologist and Toxicologist for Chevron. A jury wants to know what caused this plaintiff’s illness. Epidemiology can only speak to what raises or lowers risk across a whole population. The distance between "associated with" and "caused by" is where this kind of testimony is won or lost.
The easy thing to do is hide inside the vocabulary of the field, the relative risks and confidence intervals, confounders, and p-values. Every one of those words is precise, and every one of them is a small wall between the witness and the jury. Allison does the opposite. She builds the idea from something the jury already lives with before she ever attaches a technical name to it. A relative risk of two is not twice a hazard ratio. It is the difference between holding one raffle ticket and holding two in the same drum. Confounding is not an abstraction. It is the reason we do not blame the rooster for the sunrise. Once a juror owns the idea in plain language, the technical term stops being a barrier and becomes a convenient label for something they already understand.
“A study can tell you the odds for a thousand people. The jury’s job is one person in one chair. My job is to connect the two honestly, without overstating it in either direction.”
That honesty runs in both directions, and she is firm about it. The same discipline that keeps a defense expert from waving away a real signal is what keeps a plaintiff’s expert from inflating a weak one. A jury trusts the witness who will tell them plainly what the data can support and what it cannot. After testifying on benzene, air quality, infectious disease, and drug and alcohol matters, and after years on federal and industry panels wrestling with these exact questions, Allison has come to believe that being candid about uncertainty is not a weakness she has to manage. It is precisely what makes the strong parts of her opinion believable.
Q&A · THE HARDEST THING TO TEACH
JFP: Allison, of everything in epidemiology, what is the single hardest piece of the science to teach a jury, and how do you get them there?
AS: The hardest thing is causal inference. I am asking a jury to hold two ideas at once: that a strong association is not the same as proof one thing caused another, and that even so, we can still reach a defensible causal opinion when the evidence lines up the right way. Jurors either want a certainty I cannot honestly give them, or they hear the word association and assume it means nothing at all. Neither one is correct. I walk them through it the way an investigator actually thinks it through. Is the association strong? Does more exposure track with more disease? Did the cause come before the effect? Does it hold up across different studies and different populations? Does it make biological sense? I am not handing them a verdict. I am handing them the same checklist I use myself, and then I let them watch the evidence either satisfy it or fail it. When a jury builds the conclusion alongside me, one honest step at a time, they trust it in a way they never would if I simply announced it from the stand.
If there is one idea toxicology has to land with a jury, it is the oldest one in the field. The dose makes the poison. Kelly earned her doctorate studying chemical exposure and cancer, has spent more than 15 years in emergency response, exposure work, and occupational toxicology, and will tell you that jurors walk in with a powerful and completely understandable instinct. If something is toxic, then any amount of it must be harmful. Almost every chemical case turns on gently, taking that instinct apart and replacing it with the scientific truth – that it all depends on the dose and nature of exposure.
So, Kelly makes a dose into something you can hold. Water, caffeine, the oxygen in the room, all of them are things everyone knows are perfectly safe in ordinary amounts and dangerous in extraordinary ones. She is not trying to make light of the chemical in the case. She is planting the idea, in plain language, that exposure, concentration, and time are what turn a potential hazard into an actual risk. Once that idea is in place, the jury can weigh the actual measurements in front of them rather than reacting to a frightening word on a label.
“Everything is harmful at some dose, and almost nothing is harmful at some dose. Once a jury really understands that one sentence, the rest of the science has somewhere to land.”
Kelly is board-certified as both a toxicologist and an industrial hygienist, and that second credential gives her testimony a reach most experts do not have. She can carry a jury from what a compound does inside the body at a specific dose, all the way back to how much of it a person actually breathed, or touched, or absorbed on a given day. Connecting those two worlds, the hazard and the exposure, is where causation and risk are really decided, and it is a connection that a lot of single-discipline experts simply cannot make. Because she has drafted safety data sheets, set occupational exposure limits, performed risk assessments, and written state-of-the-art reviews, she can show a jury not only what the science says today but what was known, and what could have been known, at the time that actually matters to the case.
Q&A · THE HARDEST THING TO TEACH
JFP: Kelly, what part of toxicology gives a jury the most trouble, and how do you break through it?
KT: Dose-response is the concept I fight for in almost every case, and it fights back. People carry a mental switch, safe or poison, on or off, and toxicology lives on a dial instead of a switch. The idea that the very same molecule can be harmless at one level and dangerous at another feels, to a lot of jurors, like a lawyer’s trick. So, I do not start with the chemical in dispute. I start with something they already interact with daily: water, or the caffeine in their morning coffee, and I let them tell me that the amount is what matters. Once they have said it out loud about their own coffee, they own the principle, and I can carry it over to the compound in the case without anyone feeling cornered. The second hurdle is the difference between a potential hazard and an actual exposure or risk: what a substance can do versus what it will actually do in the given scenario. That is where my industrial hygiene side earns its keep, because I can take a jury from what the molecule does in the body all the way back to how much of it was ever in the air someone was breathing, and the relationship between the two.
The Human Factors Expert: How People Actually Perceive, Decide, and Err
Robert Rauschenberger, PhD
Cognitive psychology; visual attention, warnings, product design | Vice President, Director of Human Factors
Human factors sits in an unusual spot in a courtroom, because its subject is the jury itself. Robert studies how people take in information, where their attention goes and where it does not, how a warning gets noticed or missed, and how ordinary people make decisions in the middle of real life. That closeness is both his biggest advantage and his biggest hurdle, because every juror is already a lay expert in being human, and every one of them walks in certain they know exactly how they would have acted.
So, his job is not to teach an unfamiliar science. It is to correct a very familiar instinct, the hindsight bias that makes a missed warning or an obvious hazard look inexcusable once you already know how the story ended, and to swim upstream against strongly held but scientifically incorrect misconceptions about what captures attention, how humans make decisions, and whether a hazard was foreseeable and could have been mitigated – topics on which every juror already had an opinion before he or she entered the courtroom. What works in his favor is that there is strong empirical science even on the very biases to which jurors are subject, and that his field can, in many instances, be shown rather than argued. In addition to telling a jury how attention works, he lets them see it through an eye-tracking study, a visual-search demonstration, and a simple exercise right there in the courtroom, where the jurors themselves fail to notice something sitting in plain sight. The moment people feel the limits of their own perception, the principle stops being an abstraction, and it does so without anyone having to be told they were wrong.
“The most persuasive thing I can do is let the jury catch their own mind in the act. Once they feel how attention really works, nobody has to argue about it.”
Robert has testified in medical device, product liability, design defects, failure-to-warn, Proposition 65, and class action matters, and he has designed and tested real products in our own user-research labs, which gives him a second kind of credibility. He is not just a critic who shows up after something failed. He builds and evaluates these things before they fail. That mix of the reactive and the proactive lets him speak to a jury not as a hired critic but as a working scientist who understands, from both sides, how good design keeps people safe and how predictable human error gets them hurt.
Q&A · THE HARDEST THING TO TEACH
JFP: Robert, what is the hardest thing about human factors to teach a jury that is, itself, made of humans?
RR: Hindsight bias, and it is hard precisely because every juror is certain it does not apply to them. Once you know an accident happened, the missed warning looks glaring, and the hazard looks obvious, and it becomes almost impossible to picture not seeing it. (“Please try not to imagine a pink elephant.”) My whole field is about what people actually perceive in the moment – before anyone knew how the story would end. The trap is that if I simply tell a jury that they are biased, I have insulted them and lost them. So, I do not argue it. I demonstrate it. I will run a quick visual-search exercise, or show them the kind of attention test where people miss something sitting right in front of them, and they miss it too. That moment is everything. When jurors feel their own attention fail, in a safe and even slightly funny way, they stop judging the person in the case and start understanding them. I never have to say you were wrong. They get there on their own, which is the only way it ever really sticks. By contradicting the “common sense” of the jury, I am also able to prove that human factors is a hard science and not merely a recitation of common sense, as many are tempted to believe because they think they know the answer (when they are, in fact, wrong).
The Meteorologist: Rebuilding the Sky Over a Single Place and Moment
Daniel Schreiber, CCM
Certified Consulting Meteorologist (AMS #746); | Senior Vice President & Meteorology Practice Lead, J.S. Held
Everybody thinks they understand weather, and that is exactly what makes Dan’s job harder than it looks. Every juror has stood in the rain, been scared by lightning, and watched a forecast miss, so they walk in feeling like they already know the subject. Dan is a Certified Consulting Meteorologist and an Air Force veteran who has been retained in more than one thousand matters and testified in state and federal courts across the country, from aviation crashes to vehicle wrecks to multi-million-dollar storm-damage disputes, and he will tell you the first thing he has to do is respect that everyday familiarity while gently showing the jury that what happened at a specific place, at a specific minute, is a very different question from what the weather felt like in general or what was shown on media outlets.
The heart of forensic meteorology is reconstruction, not prediction, and that distinction is the one jurors struggle with most. A forecast is a statement of probability made before the fact. What Dan does is reconstruct what the atmosphere actually did after the fact, at a location that usually has no weather station right on top of it. He pulls it together from radar sweeps, satellite images, nearby observations, and physics, and then he has to make a jury comfortable that the nearest airport, 10 miles away, is not automatically the same weather as that over the accident site. He does it the way a good pilot briefs a mission, plainly and in order, turning a wall of data into a picture the jury can actually see in their minds.
“A forecast is a guess about tomorrow. My job is to tell a jury what the sky actually did yesterday, over one exact spot, and to show them how I know it.”
What sets Dan apart is a reputation, even among other meteorologists, for making time-sensitive and complicated weather easy to understand, which is the same skill that gets him called by media and government officials when severe weather is bearing down. In a courtroom that gift matters twice over, because a jury does not need to become meteorologists. They need to trust that the person explaining the storm has experience studying these storms, checked the radar, and is telling them straight what the sky was doing and, just as importantly, what it was not.
Q&A · THE HARDEST THING TO TEACH
JFP: Dan, of everything in meteorology, what is the single hardest thing to teach a jury, and how do you get them there?
DS: The most difficult thing to teach a jury is that weather information comes in many forms and comes from sources of varying quality and reliability. Over time, the field of meteorology has become diluted by an overwhelming amount of publicly available weather information, leading many people to believe they know as much as, or more than, a trained meteorologist. Frankly, I do not blame them. In today's world, weather forecasts, radar imagery, and weather-related opinions are available everywhere.
Because of that reality, my first responsibility is to establish trust. From the moment I begin testifying, I focus on presenting facts that are objective, transparent, and difficult to dispute. I acknowledge limitations and uncertainties when they exist, make concessions when warranted, and remain firmly grounded in where the science and evidence lead. My role is not to advocate for a particular outcome, but to explain the weather as accurately and honestly as possible.
I also believe that communication is just as important as technical expertise. Complex meteorological concepts can quickly become overwhelming, so I explain the weather event at issue in clear, straightforward language. I draw upon examples and experiences that jurors can relate to, based on their geographic location and personal familiarity with weather. Jurors appreciate witnesses who are honest, understandable, and relatable, and those qualities help ensure that the science is accessible rather than intimidating.
Ultimately, the most important point I strive to convey is that I am there to educate the jury about the weather, not to persuade them to rule in favor of the client who retained me. In my experience, litigation often becomes a battle of experts. The expert who earns the jury's trust, explains complex issues in a way that is easy to understand, and consistently follows the facts is often the one who carries the greatest weight. When jurors can independently follow the evidence from the jury box and arrive at the same conclusions, the testimony becomes far more credible and impactful.
The Geotechnical Engineer: The Ground Beneath the Case
Geotechnical failures tend to be catastrophic, always expensive, and almost never simple. Richard has led investigations into some of the largest tailings-dam failures of recent years, along with tunnel collapses, retaining-wall failures, landslides, and failed shallow and deep foundations across the Americas, Australasia, and Europe. His challenge with a jury is one of scale and of what stays hidden. The events that decide the case happen underground, over long stretches of time, through differences in soil and rock composition, with the influence of pore water pressure or groundwater conditions, total and effective stress, and with natural and anthropogenic changes or influences with time.
His approach is to tell it as a story, in order. A failure has a beginning, and the engineer’s job is to walk the jury back along the chain of cause until the starting point is impossible to miss. He leans on physical analogy to carry the mechanics. There are many ways to illustrate the impact of pore water pressure in destabilizing a slope, with one such example involving the construction of a sand castle and allowing it to stand strong in the midday sun until such time the tide rises, water permeates through its base, and the castle walls tumble. Those images are not decoration. They are what hold the testimony up, and Richard chooses them because they are true to the physics and because a juror can feel them in their own hands.
“The collapse the jury is looking at is the last page. My job is to take them back to the first page and show them how, and why, we ended up there.”
His forensic reports and his training as an accredited mediator have taught Richard that the most persuasive engineering testimony is also the most disciplined about what it refuses to claim. When causation is genuinely in dispute, he separates what he can establish from what he can only bound, and he has watched that kind of precision move sophisticated parties toward settlement more than once. A jury is not so different from a mediation table. Both of them follow the expert who shows his reasoning, respects the limits of the evidence, and never asks to be believed simply because of who he is.
Q&A · THE HARDEST THING TO TEACH
JFP: Richard, of all the mechanics of a geotechnical failure, what is the single hardest thing to teach, and how do you get a jury to see it?
RS: Integrating the concepts of effective stress and pore water pressure, explaining the process of soil liquefaction of soil slopes or tailings dams can be a challenging but also rewarding concept to explain. One starts with the composition of the soil that represents the slope, be it silts or gravels. Then imagine these soils having been placed in a very loose fashion, much like a card house structure, with the cards barely in contact with the neighboring card, and a great deal of space or void space between the cards. Now allow water or fluid to infiltrate those voids, perhaps through rainfall, natural groundwater rise, or at the onset during the deposition of these soils. Now, cause a disturbance to these soils through some sort of natural (seismic) or anthropogenic source, or a stress change which encourages the soils to seek a denser backing arrangement. As the soils try to achieve a denser packing arrangement, the water in the voids needs to move or get out of the way. If the water cannot get out of the way quickly enough, it is forced to carry the load of the soil and whatever structure is above.
We all know that water has effectively no strength, which in turn causes the soil/water slope to lose strength and “liquefy” and potentially flow. One of the best analogies to this process is driving a car in the rain. With good tire tread and driving at safe speeds, rain on the road can pass through the tire treads, maintaining good contact between the rubber and the road and the vehicle's drivability. If, however, the tire treads are poor, the car is driving at excessive speeds, and/or one encounters a deep puddle, the vehicle will hydroplane as the water cannot escape through the treads quickly enough, and the drivability of the vehicle is lost, as the water has no shear strength, not allowing one to control the vehicle.
That one image lets them feel a mechanism they will never actually see. From there, I walk them backward, one step at a time, from the collapse they are looking at to the first quiet change that started it. And I am careful to separate what I can prove from what I can only bound. My credibility as an engineer and as a mediator depends on never claiming a single inch more than the ground itself will support. I am there to serve the court and physics, providing credible, defensible advice or testimony.
Conclusion – The Through Line: Depth Earns Simplicity
Five disciplines, five very different problems, and underneath all of them the same conviction. When Allison connects a population to a single person, when Kelly makes a dose into something you can feel, when Robert lets a jury catch their own perception slipping, when Dan rebuilds the sky over one exact place and moment, and when Richard turns a buried failure into a story a jury can follow, they are all doing the same thing. They are respecting the intelligence of the people in the box while clearing away everything standing between those people and the truth.
That is what a deep technical bench really gives a client. It is not the credentials on the report or the length of a curriculum vitae. It is the rare combination of genuine mastery and the ability to teach, because only someone who truly understands a subject can make it simple without making it wrong. Our experts work at the point where science meets consequence, and their job does not end when the analysis is sound. It ends when a jury understands it.
The best expert witness is not the one who proves how much they know. It is the one who leaves the jury feeling, correctly, that they understand it too.
Hard cases are not won by whoever brings the most impressive science into the room. They are won by the side whose science the jury can pick up, weigh for themselves, and trust. Getting there takes depth first and clarity always, and it takes experts who understand that teaching a jury, without ever talking down to them, is not a nicety. It is the whole job.
John Peiserich, Esq., is an Executive Vice President and Practice Lead in J.S. Held’s Environmental, Health & Safety practice. With over 30 years of experience, John provides consulting and expert services for heavy industry and law firms throughout the country with a focus on Oil & Gas, Energy, and Public Utilities, including serving as an expert witness in arbitration proceedings and in state and federal courts. He has extensive experience evaluating risk associated with potential and ongoing compliance obligations, developing strategies around those obligations, and working to implement a client-focused compliance strategy. John has appointments as an Independent Monitor through EPA’s Suspension and Debarment Program. He routinely supports clients in a forward-facing role for rulemaking and legislative issues involving energy, environmental, Oil & Gas, and related issues.
Allison Stock, PhD, MPH, MS, is the Health Sciences Service Line Leader in J.S. Held’s Environmental, Health & Safety practice. She specializes in human health risk assessments combing both toxicological and epidemiological data. She has expertise in petrochemicals; pharmaceutical agents; environmental permitting; property transfer; environmental, social, and health impact assessments; inhalation toxicology; renal toxicology; drug and alcohol exposures; toxicological and epidemiological risk assessment; communicable and foodborne illnesses such as Legionella, Salmonellosis, and Pseudomonas infections; rapid needs assessments; emergency response; ambient and indoor air monitoring; occupational health and safety plans; and stakeholder communications.
Kelly Scribner Tuttle, PhD, CIH, DABT, is J.S. Held’s Senior Technical Fellow, Industrial Hygiene / Principal Toxicologist. She is a board-certified toxicologist (DABT) and industrial hygienist (CIH) with over 15 years of multidisciplinary experience in the fields of occupational toxicology, chemical emergency response, human and environmental toxicology, industrial hygiene, crisis communication, human health and ecological risk assessment, and exposure assessment. She has provided technical expertise for multiple projects involving chemical exposures in occupational, environmental, and consumer settings.
Robert Rauschenberger, PhD, is Vice President and Director of J.S. Held’s Human Factors practice. He has over 25 years of experience conducting research on topics of visual attention and distraction, the organization of perceptual information, product design, user experience, risk communication effectiveness, and consumer decision-making. He leverages this experience in legal cases across industries, including product liability/failure to warn cases, class actions (both at the certification and at the merits stages), Proposition 65, and web design cases, for which he has testified in depositions and at trial in both federal and state courts.
Daniel Schreiber, CCM, is a Senior Vice President in J.S. Held's Forensic Meteorology service line. He is a Certified Consulting Meteorologist with over 10 years of experience in military, aviation, and severe weather operations. Mr. Schreiber has provided consulting and expert services for both plaintiff and defense law firms, as well as insurance adjusters, appraisers, umpires, and policyholders throughout North America. He has been consulted and/or retained as an expert in over 850 matters and has testified in both depositions and during trials in state and federal courts. He regularly plays an integral role in multi-million-dollar insurance disputes and injury/wrongful death lawsuits from coast to coast. Before joining J.S. Held, Dan was a highly successful meteorology business owner.
Richard Stahl, PhD, CEng, FICE, P.Eng., is a Senior Vice President in J.S. Held’s Forensic Architecture & Engineering practice. Richard has more than 30 years of international experience as a geotechnical engineer and forensic investigator. He has led multidisciplinary teams for large-scale project developments and forensic investigations. He has provided expert testimony at trial, arbitrations, and mediations. Richard has been engaged in multi-million-dollar assignments within a variety of business sectors, including mining, energy, natural resources, industrial, commercial, heavy civil infrastructure, marine, transportation and distribution, real estate, hospitality, and tourism/recreational sectors within the Americas and Asia. Notable assignments include flooding investigations and remediation in the Bahamas, shallow and deep excavations in North America, tunneling in Asia and North America, and slopes, water resource, and mine tailings dams in North and South America and Australasia.
Transparency Statement: Artificial intelligence tools were used to support the development of this thought leadership content, which could include research support, information synthesis, and editorial refinement. The analysis, insights, perspectives, and conclusions presented are those of the author(s) and reflect their professional expertise and judgment. The content was reviewed by the author(s) for accuracy, relevance, and consistency with the source materials. Artificial intelligence tools did not independently determine the content's conclusions or recommendations.
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