On November 10, 2022, Kenneth and Phyllis Zerr perished in a house fire. Plaintiffs—the Zerrs’ children and Kenneth Zerr’s estate—alleged that the fire was caused by a defective dehumidifier produced by Gree.
To support their theory that the fire was caused by a defective dehumidifier, Plaintiffs planned to use expert witnesses. On the origin of the fire, Plaintiffs offered Robert D. Helmkamp. On potential electrical causes of the fire in the room identified as the origin, Plaintiffs offered William Truss. And on the origin of the fire within the dehumidifier and design defects in the dehumidifier, Plaintiffs offered Derek Starr.
Together, the experts purported to establish the fire’s cause by identifying the origin of the fire through Helmkamp, eliminating alternative causes through Truss, and examining the dehumidifier to establish an origin theory through Starr. All three experts purported to have relied on the National Fire Protection Association’s publication, NFPA 921: Guide for Fire and Explosion Investigations (“NFPA 921”). However, Defendants filed motions to exclude all three expert witnesses.
Fire Investigation Expert Witnesses
Robert David Helmkamp is a Certified Fire Investigator through the International Association of Arson Investigators, the National Association of Fire Investigators, the National Board on Fire Service Professional Qualifications, and the State of Missouri.
William W. Truss is a Certified Fire and Explosion Investigator (NAFI-CFEI) and a Certified Vehicle Fire Investigator (NAFI-CVFI). He is a member of the Institute of Electrical and Electronics Engineers (IEEE), the International Association of Arson Investigators (IAAI), the National Association of Fire Investigators (NAFI), and the National Fire Protection Association (NFPA).
He also graduated with Electrical Engineering and Computer Engineering Degrees from the University of Missouri – Columbia in 1987 and is a licensed professional engineer in several states.
Derek A. Starr is a professional forensic electrical engineer and fire investigator. Prior to his current employment, he spent more than six years performing certification evaluations at Underwriters Laboratories, Inc.
Discussion by the Court
I. Robert Helmkamp
To begin with, Helmkamp followed the methods prescribed by NFPA 921 in determining the fire’s origin. He analyzed witness information, fire patterns, and fire dynamics. Helmkamp also performed an inspection of the building, observing fire damage levels and patterns. He examined the exterior of the house before moving to the interior, starting in areas with the least damage and moving to the areas with the most damage. Through his inspection, he determined that the fire started in the utility room by systematically eliminating every other room as a possibility.
He then used burn patterns and relative fire damage to identify a suspect zone within the utility room. Ultimately, he concluded that “based upon fire patterns, degrees of fire damage, fire behavior indicators and electrical activity within the dehumidifier appliance, it is my professional opinion the fire originated at, or within, the dehumidifier appliance located on the floor in the basement utility room.”
Defendants also contended that Helmkamp failed to consider evidence of alternative ignition sources, including ceiling-level electrical arcing, minimally damaged combustibles, and the results of the second lab exam. Helmkamp did not ignore such evidence. In his initial report, he noted the “lack of damage observed to combustible and metal components located in close proximity nearby” and “thermal damage, likely masking evidence of electrical arcing.” And in his supplemental report, he considered the “additional investigation and data” collected at the second lab exam, including the opportunity for closer examination of the evidence of ceiling-level electrical arcing. In both reports, he found such evidence consistent with his opinion that the fire originated at or within the dehumidifier. While Defendants’ experts may disagree with Helmkamp about the significance of the evidence, Defendants have not pointed to any “total lack of consideration of .. . clear alternative ignition sources constituting ‘serious error.’”
II. William Truss
Defendants argued that Truss’ opinions must be excluded because he failed to follow NFPA 921; he relied on “negative corpus”; he conducted no testing; and he failed to consider alternative ignition sources and contradictory evidence.
As documented in his initial report, Truss followed NFPA 921’s prescribed method for fire cause determination. His report relied on three site examinations (two of which were joint examinations), a laboratory examination, Helmkamp’s report and several other documents and procedures.
Truss identified and analyzed electrical artifacts in the area of origin. Truss then systematically eliminated the electrical artifacts other than the dehumidifier as potential causes. He began by eliminating artifacts that were substantially outside the area of origin. Then he eliminated artifacts that showed no evidence of an electrical failure. That left four electrical artifacts that could have been the cause of the fire. Truss then individually evaluated the hypotheses that each of the remaining artifacts contributed to the cause of the fire, explaining why he found that three of them were “inconsistent with the facts and the principles of science.”
Defendants argued that Truss’ opinion should be excluded because his evaluations of alternative ignition sources lacked “scientific testing, analysis, measurements, calculations, empirical data, or peer-reviewed literature,” but that does not defeat its admissibility.
However, no specific kind or quantity of “testing” is necessary for Truss’ testimony to qualify as reliable. His evaluations of the four hypotheses cite observations of physical evidence and his own experience.
Truss addressed “the additional investigation and data collected” in a supplemental report, finding that none of it was in conflict with his earlier opinions.
III. Derek Starr
A. Starr’s opinion on the origin of the fire is admissible
Starr’s opinion was not based only on internal damage to the dehumidifier; he also relied on the opinions of Helmkamp and Truss. Starr also did not ignore the results of the second lab exam. He considered the findings and concluded that they did not support an alternative hypothesis or conflict with his previously stated opinion. Resolving the experts’ disagreements as to the significance of the second lab exam is a job for the jury.
Therefore, the Court held that Starr’s methods in determining that the fire originated internally to the dehumidifier—relying on observations of physical evidence, scientific principles, experience, and the opinions of Plaintiffs’ other experts—were consistent with NFPA 921.
B. Starr’s opinion relating to UL certification is admissible
Defendants objected to Starr’s opinions relating to the dehumidifier’s UL listing because (1) he ignored the absence of a pattern of dehumidifier fires prior to 2012 and evidence that Plaintiff Hillman purchased the dehumidifier in May 2011, (2) he provided no timeline as to when the UL listing would have been removed and whether it would have actually prevented the sale of the dehumidifier if it was purchased in May 2011, and (3) he did not sufficiently explain UL standards or decision-making processes or “provide any evidence that exceeding a temperature rating under similar testing would automatically trigger removal of the UL Mark.”
Analysis
In his initial report, Starr explained what a UL listing is, what purpose it serves, and the requirements UL imposes on manufacturers, including the duty to inform UL if a manufacturer becomes aware that a certified product could pose a “substantial hazard.”
Starr’s second supplemental report explained why the November 2010 Low Refrigerant Charge Operation Test of a GE-branded dehumidifier is relevant to the dehumidifier at issue in this case; what the test results were; and why they were indicative of a fire hazard. Finally, he opined that the test provided Gree with “knowledge of a substantial hazard to users,” which triggered its duty to notify UL, and would have jeopardized its UL listing.
Defendants also objected that Starr ignored the evidence that Hillman purchased the dehumidifier in 2011 and “provided no timeline as to when the UL listing would have been removed and/or whether this would have actually prevented the sale of the subject Dehumidifier.”
But—as far as the Court can tell—Starr’s opinion did not appear to rest on a disputed fact. His opinion did not assert that decertification would have happened on any particular timeline or prevented any particular sale, and it also did not rest on any claims about reports of dehumidifier fires.
IV. The Experts’ Testimony will not be Excluded under Rule 403
Defendants also argue that all three experts’ testimony should be excluded under Federal Rule of Evidence 403, because its probative value is substantially outweighed by the danger of confusing or misleading the jury. The Court disagreed. All three experts’ opinions are probative of critical issues the jury will have to decide, and the Court has seen no evidence that they would pose a significant risk of confusing or misleading the jury.
Held
The Court denied Defendants’ motions to exclude the testimony of Plaintiffs’ experts Robert Helmkamp, William Truss, and Derek Starr.
Key Takeaway
In the context of fire investigations, expert opinions formed on the basis of observations and experience may meet the Rule 702 reliability threshold. Similarly, an expert opinion based on the NFPA 921 investigative guidelines for fire investigations meets this reliability threshold if NFPA 921 is applied reliably.
Case Details:
| Case Caption: | Hillmann V. Gree USA, Inc. |
| Docket Number: | 4:23cv830 |
| Court Name: | United States District Court, Missouri Eastern |
| Order Date: | March 16, 2026 |
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