Rule 702 Expert Exclusion: Lessons from Wolff v. Tomahawk

December 19, 2025
Expert Testimony, Intellectual Property, Valuation

Written by Chris Walton, JD

Six Experts In, Two Out: Rule 702 and the Pretrial-Disclosure Trap in Wolff v. Tomahawk Manufacturing

The plaintiff in Wolff v. Tomahawk Manufacturing proffered six expert witnesses. The defendant moved to exclude every one of them. When the dust settled, two were left standing — three damages and technical experts excluded under the amended Rule 702, and a fourth, a treating physician, struck on a separate motion for a pretrial-disclosure failure unrelated to reliability. It is the most granular multi-expert admissibility ruling in the current pipeline, and a warning: gatekeeping can thin a roster before trial begins, and not every expert falls for the same reason — or even under the same rule.

First, what the case is. Despite the reasonable-royalty machinery that drives the damages dispute, Wolff is not a clean trade-secret-misappropriation suit. James B. Wolff sued his former employer for breach of a non-disclosure agreement, whistleblower retaliation, and disability discrimination; a trade-secret “theft of technology” damages theory rides along, and the court borrowed patent-law reasonable-royalty principles by analogy to evaluate it. (Mind the two Wolffs: the plaintiff is James B. Wolff; one of the excluded damages experts is his daughter, Elisabeth Wolff.) Two of the six challenged “experts” are treating physicians whose fate turned on disclosure mechanics, not Daubert. In Wolff v. Tomahawk Mfg., No. 3:21-cv-880-SI (D. Or. June 2, 2025), Judge Michael H. Simon ruled on each expert independently and reached a different result for nearly each one.

When You Don’t Need This Case

Wolff earns its keep only if you are assembling a multi-expert damages-and-technical roster in an IP or trade-secret matter. If your case turns on a single retained expert, the roster-audit framing below is overhead — the lesson collapses to the ordinary one: tie the opinion to the facts and to the governing analytical framework, or lose it. If you are past disclosure with a clean witness list, the procedural cautions won’t move you either. Everyone else: this is a case-by-case map of what survived and what did not.

Six Experts, Two Survivors

The court took the roster apart one expert at a time. The scorecard:

Elisabeth Wolff — excluded. The plaintiff’s daughter, offered as a damages expert. She was excluded first for lack of qualification — a biology degree, a ten-week bookkeeping course, no business-valuation experience, no familiarity with the Georgia-Pacific factors — and, independently, as unreliable. Handed an editable spreadsheet and sales figures from another of the plaintiff’s experts, she transferred the numbers and applied either 100% of gross sales or a royalty figure lifted from a separate agreement. The court called it “merely arithmetic” — not a methodology, and not helpful to a jury.
Langston Murray — excluded. A second damages expert, and substantially the same failure. Murray holds an MBA in project management but could not define “GAAP” or “LLC,” had never valued a business, and had never heard of the Georgia-Pacific factors. Like Wolff, he applied the royalty terms from the FOT Agreement — an agreement between affiliated entities, for different technology, that is not part of this case — to gross sales, without explaining why those terms should govern a hypothetical negotiation between these parties. The court analyzed him in express parallel to Wolff.
Samuel Gannon — excluded. The one genuinely distinct exclusion. Gannon is a qualified mechanical engineer and former Tomahawk employee, and the court found him qualified. His opinion failed anyway because nothing under it was testable: he never tested whether the tooling-and-timing combination he identified actually reduced pressure, never compared it against other configurations, and ultimately fell back on his experience and on deferring to Wolff. An expert may rely on experience, but the opinion must still rest on sufficient facts or data. Gannon’s was ipse dixit.
Mith Leng — excluded (procedurally). A treating physician on the disability claim. Tomahawk attacked his disclosure and lost: the court held his Rule 26(a)(2)(C) disclosure sufficient and rejected the Daubert challenge. He was excluded on a separate motion in limine, because the plaintiff failed to list him on the trial witness list the court’s Trial Management Order required. The defect was a witness-list omission — not an inadequate or late report — and a prior disclosure does not cure it.
Charles Sweat — admitted. A technical expert with nineteen years in meat-forming who had supervised Wolff at Tomahawk. What separated him from Gannon was concrete: Sweat actually tested the pressure changes while developing the technology, reading the gauges himself. The defense’s points — that other factors might explain the pressure drop, that he had not reviewed a competitor’s patents, that he was Wolff’s friend — all went to weight, not admissibility.
Brian Kearns — admitted. Wolff’s treating hematologist, offered on the disability claim. The court ran no reliability analysis on Kearns; it denied the challenge because his Rule 26(a)(2)(C) disclosure adequately stated his diagnoses, treatment, and opinions, and he appeared on the witness list, so there was no unfair surprise. Here the disclosure mechanics did the work.

Two of the three Rule 702 exclusions, then, are the same failure: an unqualified author applying a borrowed royalty to gross sales on a mistaken premise about which technology was at issue. Only Gannon presents a separate defect. And the survivors split as cleanly — one technical expert who tested what he claimed, and one treating physician admitted on the strength of his disclosure.

The Georgia-Pacific Problem

Both damages experts foundered on the same framework gap, and it is worth isolating because it is specific to IP and trade-secret damages. A reasonable royalty is typically built from a hypothetical negotiation analyzed through the Georgia-Pacific factors — the fifteen-factor framework from Georgia-Pacific Corp. v. U.S. Plywood Corp., 318 F. Supp. 1116 (S.D.N.Y. 1970), applied to trade-secret cases by analogy. The factors run to comparable licenses, the licensor’s established licensing policy, the commercial relationship between the parties, the IP’s contribution to profit, and the terms a hypothetical negotiation would have produced.

Gesturing at the factors is not enough. As the court emphasized, quoting the Federal Circuit, an expert must explain how the rate was calculated using them and tie the analysis to the facts. Neither Wolff nor Murray did; both imported a number from an agreement covering different technology between different entities. For a valuation professional taking an IP or trade-secret engagement, the rule is blunt: if you cannot name the framework your opinion will be measured against — and show your work inside it — the number is an assertion, and it will be excluded.

The Testing Requirement for Technical Experts

Gannon’s exclusion isolates the requirement that bites technical and engineering experts: the opinion must rest on sufficient facts or data, which for an engineer means testing, measurement, or analysis of physical evidence. “In my experience this would happen,” untested, is an opinion a court cannot evaluate. The financial analogue is exact — “in my judgment the rate is 5%,” without comparable licenses or a Georgia-Pacific analysis, is the untested engineering opinion in a different suit.

One point of precision, because the easy version of this argument overreaches. The court did not need the 2023 amendment to exclude Gannon; it relied on settled law that an expert’s ipse dixit cannot bridge the gap between data and conclusion. What the 2023 amendment changed, more broadly, is posture: the proponent must now show sufficiency and reliable application by a preponderance, as admissibility questions for the court rather than weight questions for the jury. That shift will catch the next expert whose foundation is thin — but Gannon would have failed under either regime.

The Expert-Admissibility Cluster

Wolff takes its place in a line of decisions mapping the range of Rule 702 / Daubert / Frye outcomes:

Total exclusion — wrong credentials. Sullivan v. Loden, 2022 WL 1409567 (D. Haw.). A respected estate attorney was not qualified to opine on business valuation.
Total exclusion — unreliable tool. Matter of Weber, 220 N.Y.S.3d 620 (Sur. Ct. 2024). An expert’s AI-assisted (Copilot) figures were non-reproducible and unvalidated, and he could not explain his inputs.
Partial exclusion — mixed components. BBK Tobacco & Foods LLP v. Central Coast Agric., Inc., No. 2:19-cv-05216, ECF 547 (D. Ariz. Jan. 31, 2025). Some opinions survived; unsupported assumptions and undisclosed evidence did not.
Multi-expert thinning. Wolff v. Tomahawk Mfg. Three damages and technical experts out under Rule 702, one treating physician struck on a witness-list omission, two admitted.
Full admission — record-anchored judgment. Yador v. Mowatt, 2024 U.S. Dist. LEXIS 163727 (E.D.N.Y.). A comparable-company selection survived because the choices were tied to record evidence and the data came from the comparables themselves.
Full admission — data-driven simplicity. Kirkbride v. The Kroger Co., 349 F.R.D. 160 (S.D. Ohio 2025). A deliberately simple, formulaic damages model survived because it ran on the defendant’s own records — the simplicity went to weight, not admissibility.

Set Kirkbride against Wolff and the real lesson surfaces. A one-line formula can be admissible when its inputs are the defendant’s verified data; arithmetic fails when the inputs are borrowed and unexamined. The difference is not the complexity of the math — it is whether the number is tied to the facts.

The Roster Audit

If you are assembling an expert team for a trade-secret or IP damages case after Wolff:

Confirm each expert knows the governing framework. A reasonable-royalty expert must work the Georgia-Pacific factors; a lost-profits expert, the Panduit test; a trade-secret expert, unjust enrichment and the reasonable-royalty alternative under the DTSA. An expert who cannot name the framework their opinion will be judged against is exposed.
Require data or testing for every technical conclusion. Testing, measurement, or analysis of physical evidence — not “in my experience.”
Separate methodology from arithmetic. Multiplying a rate by a base is arithmetic. The methodology is how the rate was derived and the base established. If the inputs cannot be defended, the math goes with them.
Police the pretrial filings, not just the reports. Leng was not struck for a bad report — his disclosure was held sufficient. He was struck for being left off the trial witness list the scheduling order required. Disclosing a witness earlier does not excuse omitting them from the filings the court actually demands.
Audit the whole roster before the motion lands. Wolff lost three of six. The defense targets the weakest expert first, and where opinions are interdependent, one exclusion can destabilize the rest. Evaluate each expert independently — exactly as the court will.

The Practical Takeaway

Wolff v. Tomahawk Manufacturing is gatekeeping at scale: six experts in, two out, with no two exclusions alike at the level of doctrine — unqualified arithmetic, untested engineering, a witness-list omission. The survivors held for reasons statable in a sentence: one tested what he claimed; one was a treating physician whose disclosure was clean. A strong lead expert does not rehabilitate a weak one. A polished CV does not open the door. The court took the roster apart one expert at a time. Build yours the same way.

Chris Walton, JD, is President & CEO of Eton Venture Services. He can be reached at [email protected].

If you’re preparing a damages analysis in a trade-secret or IP matter and want the reasonable-royalty opinion built on the Georgia-Pacific framework — or you want a roster stress-tested before a multi-expert Daubert motion is filed — I’m happy to talk through the approach. The audit before the motion is the most cost-effective expert preparation there is.