The Subrogation Strategist

In Amp Servs., LLC v. Auto-Owners Ins. Co., No. 5:24-CV-00235-MEO-DCK, 2026 U.S. Dist. LEXIS 231369, the United States District Court for the Western District of North Carolina (District Court) considered whether to exclude the opinions of the defendant insurer’s fire investigator, who concluded that a warehouse fire was incendiary. The District Court granted in part and denied in part the plaintiffs’ motion to exclude, holding that the investigator’s causation opinion was not a reliable application of his chosen methodology because he failed to eliminate two competent ignition sources in the area of origin. The District Court nevertheless permitted the investigator to testify to his observations and to certain limited opinions, including the fire’s origin.

On July 11, 2023, a fire began in the basement storage room of a warehouse owned by plaintiff Austin Powell in Granite Falls, North Carolina. The room contained unused pine straw and a stack of tires. An orange extension cord, plugged into a receptacle in an adjacent room, ran into the storage room, and a metal electrical conduit that had been mounted to the wooden ceiling was found after the fire on the floor in the pine straw. Mr. Powell submitted a claim to his insurer, the defendant, in this case. The defendant retained a fire investigator to determine the origin and cause of the fire. The investigator concluded that the fire was incendiary, ignited by a halogen spotlight placed beneath the pine straw and tires, and stated in his report that there were no other potential ignition sources, and no electrical conductors, in the area of origin. The plaintiffs moved to exclude the fire investigator’s report, opinions, and testimony.

The District Court explained that, under Federal Rule of Evidence 702, the proponent of expert testimony must demonstrate that it is more likely than not that the expert’s opinion reflects a reliable application of the principles and methods to the facts of the case. Whether an expert reliably applied his method is a question of admissibility for the court, not merely one of weight. The fire investigator purported to follow NFPA 921, the Guide for Fire and Explosion Investigations, which requires that every competent ignition source in the area of origin be tested as a hypothesis and eliminated only if there is reliable evidence that it could not be the ignition source. NFPA 921 also cautions against eliminating a source merely because there is no obvious evidence for it, and directs that, where two or more hypotheses cannot be rejected, the cause must be classified as undetermined. The court noted that the Fourth Circuit previously affirmed the exclusion of a fire investigator who failed to exclude other reasonable causes.

Applying these principles, the District Court found that the fire investigator did not reliably eliminate the extension cord. The investigator agreed that the cord was in the area of origin and was a potential ignition source. When asked how he excluded it, he testified, “I couldn’t exclude it,” and admitted that he “didn’t do anything” to determine whether its connection faulted. He conceded that the cord’s severance “could have been” caused by fire attack, arcing, or mechanical damage, and described his method of elimination as “cognitive testing…[b]asically I thought about it, put all this together.” The court held that this was not elimination based on reliable evidence as NFPA 921 requires.

The District Court reached the same conclusion regarding the conduit. Although the investigator’s report stated that there were no electrical conductors in the room, he testified that a conduit carrying conductors ran through the room and was a potential ignition source. He excluded it based solely on an exterior, visual examination, without examining the conductors, and acknowledged that he was not an electrical engineer and was “not competent to testify” that the conduit was not the source of the fire. He further agreed that nothing in the scene photographs eliminated the hypothesis that the conduit overheated the ceiling and dropped burning material into the pine straw, conceding that it “could have” started the fire.

The court also rejected the defendant’s argument that the investigator’s opinion was reliable because every other expert agreed that the fire was incendiary. An expert may rely on what others observed, but not on their conclusions about cause. Nor did the fire investigator’s testimony that the cord and conduit were “possible but not more likely than not” causes of the fire save his opinion, as that view rested on “[n]o scientific testing.” As the court put it, “[r]anking unrejected hypotheses is not eliminating them.” Accordingly, the court excluded the fire investigator’s causation opinion and his report.

The District Court did not, however, bar the fire investigator from testifying altogether. Relying on his experience as a fire investigator, the court permitted him to describe his scene examination, to opine that the fire originated at floor level among the pine straw and tires; to explain how the fire developed, to opine that the building’s electrical service, breaker panels, and gas service showed no evidence of involvement, and to testify that his visual examination of the conduit revealed no visible signs of electrical activity. He was not allowed to testify that the fire was incendiary, that the spotlight was the ignition source, or that the cord, conduit, or any other source was excluded, eliminated, or ruled out. The court noted that these limits mirror its ruling that the plaintiffs’ expert may not opine that the conduit caused the fire.

The Amp Services case confirms that federal courts in the Fourth Circuit will closely scrutinize whether a fire investigator actually applied NFPA 921, not merely whether he invoked it. An investigator who cannot point to reliable evidence eliminating each competent ignition source in the area of origin risks exclusion of his opinion, even where other experts share his conclusion. Subrogation professionals should ensure that their origin and cause experts document the testing or analysis used to rule out every potential ignition source, retain qualified engineers to examine electrical components where necessary, and be prepared to classify a cause as undetermined when competing hypotheses cannot be rejected. Conversely, when facing an opposing expert, a careful deposition focused on how each alternative source was eliminated may provide the foundation for a successful Daubert challenge.