A Daubert motion asks the trial court, acting as evidentiary gatekeeper, to exclude an opposing financial-damages expert before the jury ever hears the opinion. The motion succeeds when the expert’s methodology is unreliable, his assumptions are untethered from the record, or his conclusions rest on nothing more than his own say-so. It usually fails when the alleged defects are ordinary disagreements that belong in cross-examination rather than in a ruling on admissibility.
I am Joey Friedman, a CPA, Accredited in Business Valuation, and a forensic accountant who prepares economic-damages opinions and serves as a testifying expert. Over many engagements across commercial, manufacturing, retail, restaurant, and motor-vehicle matters, I have written reports built to survive a Daubert challenge and I have assessed opposing reports to determine where they were vulnerable. This article explains how the Daubert framework works, the most common grounds courts use to exclude a damages expert, and what a credible methodology looks like when the challenge comes.
What the Daubert standard actually requires
The modern gatekeeping rule grew out of a series of United States Supreme Court decisions in the 1990s that reshaped how federal trial judges handle expert testimony. The first established that a trial judge must confirm that expert testimony is both relevant and reliable before it reaches the jury. The reliability inquiry focuses on the expert’s reasoning and method: is the underlying approach sound, and has it been applied properly to the facts of this particular case?
To make that assessment, courts weigh several non-binding considerations. These include whether the theory or technique can be and has been tested, whether other professionals in the field have vetted it through publication and independent scrutiny, its known or potential error rate, the existence of standards governing how it is used, and whether it enjoys general acceptance in the relevant field. These are guideposts, not a rigid checklist. A method that does not map neatly onto every factor can still be admissible, and a method that nominally checks every box can still be excluded if it was misapplied.
Two later decisions sharpened the rule in ways that matter directly to financial-damages work. One held that a court is not required to accept an opinion connected to the data only by the expert’s personal authority; when the reasoning that carries the expert from his inputs to his conclusion is stretched too thin to bridge them, the testimony can be kept out even when the broad methodology is a recognized one. The other confirmed that the gatekeeping obligation extends beyond hard science to technical and specialized knowledge, which is the category that economic-damages and lost-profits testimony falls into. Together, these holdings put it beyond dispute that a lost-profits or business-damages opinion is subject to the same reliability screening as any scientific evidence.
It is worth noting that most state courts have either adopted these federal standards or apply a comparable gatekeeping procedure. A smaller group still follows the older “general acceptance” approach, which asks only whether the principle underlying the opinion is sufficiently established to have gained acceptance in its field. An expert and the retaining attorney should always confirm which standard governs in the forum where the case is pending, because the analysis and the strength of a motion can differ from one jurisdiction to the next.
The gatekeeping role is narrow, not a substitute for the jury
A point that gets lost in the heat of litigation is that the gatekeeper’s job is limited. The court decides whether an opinion is reliable enough to be helpful to the fact-finder. It does not decide whether the opinion is correct, and it is not supposed to replace the adversary system. The Supreme Court has been explicit that vigorous cross-examination, the presentation of contrary evidence, and careful jury instructions are the traditional tools for attacking shaky but admissible testimony. Wholesale exclusion is reserved for the opinions that genuinely cannot assist the jury.
This is why so many challenges fail. When an expert works from incomplete information but uses a coherent, recognized approach, the resulting imperfections usually go to the weight a jury should give the opinion, not to whether the jury hears it at all. The practical question for any motion, then, is not “are there flaws?” Every opinion has flaws an adversary can identify. The real question is which flaws are serious enough to cross the line from a cross-examination point into a basis for exclusion. Distinguishing the two is the heart of an effective Daubert strategy, and it is also the discipline I apply to my own work before a report ever leaves my desk.
How and when a Daubert challenge is raised
A challenge to a damages expert can surface in several procedural settings. The most familiar is a pretrial hearing devoted to the issue, but a formal hearing is not mandatory. A court can also resolve the question on a motion in limine, on a trial objection, or, less ideally, on a post-trial motion. Judges generally expect these challenges to be raised on a defined schedule and tend to be skeptical of an objection that surfaces late when the grounds were known earlier. Courts have rejected eleventh-hour challenges as untimely, reasoning that gatekeeping is meant to be an orderly process rather than a trial-day ambush. The lesson for both sides is to raise reliability concerns within the deadlines the court sets and to make a clear record so that any ruling can be reviewed on appeal.
Strategic calculus before filing a motion to exclude
Filing a motion to exclude an opposing damages expert is not a free move. The upside is substantial: if the court strikes the plaintiff’s only damages expert, the plaintiff may be unable to prove the amount of its loss to the required degree of certainty, which can put the entire claim at risk. That possibility is exactly why these motions are filed.
The downside deserves equal attention. A denied motion does not advance the case, and it hands the opposing expert and counsel a detailed roadmap of every perceived weakness, along with time to repair the opinion before trial. If the defects are the kind an expert can credibly explain or shore up, telegraphing them early can blunt the cross-examination that would otherwise have done real damage in front of the jury. By contrast, when a flaw is too fundamental to fix or the error is too late to cure, raising it can be worthwhile even if exclusion is unlikely, because it educates the judge on a contested issue and can shift the settlement dynamic. Experienced counsel weigh these tradeoffs deliberately, and sometimes the stronger play is to hold a point in reserve for trial rather than to disclose it in a motion.
If you want a fuller picture of how a damages opinion is built and defended from the start, I cover that in my overview of working with an economic damages expert witness.
Common grounds courts use to exclude a financial-damages expert
Beyond the formal reliability factors, courts have developed a recognizable set of recurring problems that get damages experts excluded. The themes below appear again and again in the case law, and each one is something I deliberately guard against when I prepare an opinion.
The opinion is unmoored from economic reality
A projection that no rational business would adopt for itself is a frequent target. When an expert builds a damages number on a forecast that outruns the company’s own business plan, or extrapolates a brief stretch of early success into years of soaring profits, courts have treated the result as too detached from reality to support a verdict. Estimates and reasoned assumptions are permitted, even necessary, in damages work, but they must connect to facts a sensible person in the business would recognize.
The loss is not tied to the wrongful conduct
A damages opinion has to do more than show that revenue fell. It has to link the decline to the conduct at issue and account for other plausible causes, such as broader market conditions, increased competition, pricing changes, or shifts in customer demand. An expert who simply assumes the defendant caused the entire loss, or who ignores alternative explanations, invites exclusion. The causation bridge between the wrong and the dollars is something a credible analysis addresses head-on rather than assuming away.
Assumptions lack any factual foundation
Experts are allowed to rely on assumptions, but the assumptions need support somewhere in the record or in the expert’s own defensible analysis. When the chain of reasoning rests on figures supplied by the client with no independent corroboration, or on projections the expert never tested against actual results, courts grow wary. The classic failure is an opinion connected to the data only by the expert’s authority, with no way for the jury to evaluate the underlying premises. The “garbage in, garbage out” concern is real, and an opinion built on unsupported inputs is exposed.
The expert ignored costs or confused the measure of loss
In most settings, the recoverable loss is net profit, not gross revenue or gross sales. An expert who calculates lost revenue while disregarding the variable and incremental costs that would have been incurred to earn it has not measured damages at all. Courts routinely treat the failure to deduct appropriate costs as a reliability defect. Equally fatal is matching the wrong measure of damages to the legal theory of the case, such as offering a lost-profits calculation where the claim actually calls for a different measure of recovery.
The reasonable-certainty threshold is not met
Damages must be proven with reasonable certainty. Absolute precision is not required, and the law tolerates reasoned estimation, but the opinion has to give the jury some principled means of arriving at a number. This standard is where many new-business and emerging-venture claims run into trouble, because there is little or no operating history to anchor a forecast. A purely speculative projection, or one that leaps to enormous future figures without a grounded basis, will not satisfy the requirement. I discuss this threshold in depth in my article on reasonable certainty in lost profits.
The comparison or model is not genuinely comparable
Lost profits are frequently proven through a “before and after” analysis, which compares the business’s own performance before and after the wrongful event, or through a “yardstick” comparison to similar businesses or markets. Both methods are accepted, but each depends on a real fit. A yardstick built from businesses that differ in size, location, or circumstances, without any effort to confirm true comparability, is vulnerable. The “before and after” approach tends to be sturdier precisely because it draws on the company’s own historical operating records rather than on outside proxies that may not match.
Qualifications, scope, and consistency problems
Several recurring problems concern the expert rather than the numbers. Courts are skeptical of a witness opining far outside his field, of an expert who appears to be merely repeating another specialist’s conclusions, and of a “hired gun” who claims expertise across an implausibly broad range of subjects. Experts have also been excluded for failing to follow their own stated practice, for example testifying that their normal procedure is to corroborate client-provided data and then skipping that step, and for taking a position on methodology that contradicts what they swore to in an earlier case without a coherent explanation for the difference. Finally, an opinion or component that was never disclosed in the report or deposition can be barred at trial, so completeness and consistency in the written work product matter as much as the substance.
How a credible methodology survives the challenge
The encouraging reality is that a well-built damages opinion is hard to exclude, because the gatekeeping standard is designed to let reliable, helpful testimony reach the jury. From the perspective of someone who prepares these opinions, surviving a Daubert motion comes down to a handful of disciplines applied consistently.
- Anchor every number to a verifiable source. Tie projections to the company’s own historical financial records, tax returns, industry data, or documented contracts rather than to unsupported say-so. When I rely on client-provided information, I assess it for reasonableness and corroborate it where I can rather than accepting it at face value.
- Use an accepted method and apply it correctly. A “before and after” comparison, a yardstick analysis against genuinely similar businesses, or a sound projection tested against actual results are all recognized approaches. The method has to fit the facts of the specific business and the specific theory of liability.
- Address causation directly. Identify the other factors that could have affected the result and account for them, so the opinion isolates the loss attributable to the conduct at issue instead of sweeping in every adverse development.
- Measure the right thing. Calculate net profit, deduct the costs that would have been incurred to earn the revenue, and make sure the measure of damages matches what the legal claim actually allows.
- Show the work. Lay out the inputs, the sources of each input, the assumptions made and why they are reasonable, and the calculations performed, so the analysis can be followed, tested, and defended. Transparency is what converts an estimate into a reliable opinion.
- Keep the report complete and internally consistent. Disclose every opinion to be offered, avoid contradicting positions taken in prior matters without explanation, and follow my own stated standard of practice in this engagement as in every other.
When those disciplines are in place, the typical Daubert challenge gets reframed as exactly what the Supreme Court said it should be: material for vigorous cross-examination, not a basis for exclusion. That is the standard I hold my own work to, and it is the lens I use when I assess an opposing expert’s report for an attorney deciding whether a motion to exclude is worth filing. For broader context on how damages claims are structured and quantified, see my overview of economic damages.
FAQ
What is a Daubert motion?
A Daubert motion is a request that the trial court exclude an opposing expert’s testimony because the methodology is unreliable, the assumptions lack factual support, or the conclusion is connected to the data only by the expert’s own authority. The judge acts as a gatekeeper, deciding whether the opinion is reliable and relevant enough to be presented to the jury. It is the primary procedural vehicle for keeping a flawed financial-damages opinion out of evidence.
What is the difference between a Daubert challenge and cross-examination?
A Daubert challenge asks the judge to keep an opinion away from the jury entirely, while cross-examination attacks an opinion the jury has already been allowed to hear. Courts reserve exclusion for opinions that are genuinely unreliable or unhelpful. Ordinary disagreements about assumptions, inputs, or judgment calls usually go to the weight a jury should give the testimony, which means they are addressed through cross-examination rather than through exclusion.
What are the most common reasons a damages expert gets excluded?
The recurring grounds include forecasts detached from economic reality, a failure to tie the claimed loss to the wrongful conduct, assumptions with no support in the record, ignoring the costs needed to earn the revenue so that only gross figures are presented, failing to meet the reasonable-certainty standard, and using a comparison or model that is not genuinely comparable to the business at issue. Qualification and disclosure problems also lead to exclusion.
Does Daubert apply in state courts?
Many state courts have adopted the Daubert framework or apply a similar reliability-based gatekeeping procedure, while a smaller number still follow an older “general acceptance” standard or their own existing rules on expert evidence. Because the governing standard and the strength of a challenge vary by jurisdiction, the retaining attorney should confirm which test applies in the specific forum before filing or defending a motion.
Can a strong damages opinion still be challenged?
Yes. An opposing party can file a motion against almost any expert, and the existence of a challenge says little about its merit. A methodology that is anchored in verifiable data, applies an accepted approach correctly, addresses causation, measures net loss, and shows its work is well positioned to survive. In that situation the challenge typically gets redirected into cross-examination instead of resulting in exclusion.
How do I know whether to file a motion to exclude the other side’s expert?
It depends on whether the defects are fundamental or fixable. A flaw that is too late or too serious to repair can justify filing, because it may end the opposing claim or improve the settlement posture. A flaw the opposing expert can credibly explain or correct may be better held for trial, since filing early reveals the strategy and gives the other side time to shore up the opinion. This is a judgment call, and it is one I help attorneys work through when I assess an opposing report.
About the Author
Joey Friedman is a CPA, Accredited in Business Valuation (ABV), and forensic accountant who holds a Master of Accounting and a Master of International Business and is a member of the AICPA and the Association of Certified Fraud Examiners. He also holds a Florida real estate license. Beyond those credentials, he has personally owned and operated more than a dozen of his own businesses across industries including marketing, printing, transportation, restaurants, hospitality and entertainment, and event planning — so he builds damages opinions designed to survive a Daubert challenge with both a forensic accountant’s rigor and an owner-operator’s first-hand grasp of how real businesses make and lose money.