Fire origin and cause investigator
Expert class library · Product engineering · Either side
Determines where a fire started and what caused it, following the NFPA 921 scientific method, in subrogation, product liability, insurance arson-defense and criminal arson cases. Courts treat NFPA 921 as a flexible guide rather than a checklist: an investigator who systematically tests and eliminates hypotheses is usually admitted even without physical testing, while one who cannot pin down an origin or rule out other causes is not.
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What this expert is retained to answer
- Where did the fire start, and what fire patterns, witness accounts and scene evidence support that area of origin?
- What ignition sources were in the area of origin, and how was each one tested and ruled in or out?
- Did the investigation follow NFPA 921, and if it departed from the guide, why, and does the departure matter?
- Was physical testing feasible, and if it was not done, how were the hypotheses tested analytically?
- Did the investigator reach a conclusion before reviewing all of the data, or rely on information outside the fire evidence such as a suspect's history?
Methods
- NFPA 921 scientific method
- Fire pattern analysis
- Hypothesis testing and elimination
- Witness interviews and scene documentation
- Evidence collection and arc mapping
How the testimony is attacked
- No physical testing. Challengers argue NFPA 921 requires experiments. In Allstate Indemnity Co. v. Dixon the Eighth Circuit rejected that reading, holding that hypotheses can be tested analytically against the known facts and science, and in Dalton v. McCourt Electric the court admitted an electrical fire cause opinion although further testing was feasible.
- Origin never established, causes never eliminated. Opponents attack a cause opinion offered without a defined origin or without ruling out other ignition sources. In Larsen v. 401 Main St. the plaintiff's engineer conceded his opinion did not follow NFPA 921 and could say only that the fire was consistent with a boiler failure, and the Nebraska Supreme Court affirmed his exclusion and summary judgment.
- Contradicted by eyewitnesses. Defendants argue the opinion conflicts with what witnesses saw. In Elosu v. Middlefork Ranch the Ninth Circuit held that a trial court which excluded an investigator for that reason had weighed the evidence and demanded corroboration, when Rule 702 requires only a sufficient foundation.
- Expectation bias. Challengers say the investigator formed a theory early, for example from witness interviews or a suspect's history. In United States v. Hernandez the Tenth Circuit noted that NFPA 921 itself directs investigators to gather witness accounts and found no sign the investigator reached conclusions before analyzing the data.
- Opinions that go beyond the fire evidence. Even an admitted investigator may be cut back to opinions the physical evidence supports. In Hernandez the district court admitted the investigator's origin and accelerant opinions but excluded his opinions that separate points of origin showed the fire was not accidental.
What the public record shows
A deliberately narrow CourtListener search, ("NFPA 921" OR "origin and cause") AND fire AND expert AND (Daubert OR "Rule 702"), returned 40 opinions filed since 2015, as of October 3, 2026; broader searches return more. 5 rulings that show how courts handle this class of testimony:
| Outcome | Case | Court | Why |
|---|---|---|---|
| Admitted | Dalton v. McCourt Electric LLC112 F. Supp. 3d 320 | E.D. Pa. 2015 | The court denied Daubert motions against the plaintiffs' fire cause expert, holding that narrowing three hypotheses by deductive reasoning was a systematic approach consistent with NFPA 921 and that the lack of further feasible testing went to weight. |
| Excluded | Larsen v. 401 Main St., Inc.302 Neb. 454, 923 N.W.2d 710 | Neb. 2019 | The Nebraska Supreme Court affirmed exclusion under Daubert and Schafersman of the plaintiff's engineer's fire cause opinion, which conceded it did not follow NFPA 921, could not rule out other causes and could say only that the fire was consistent with a boiler failure, while the defense fire investigator's testimony was allowed. |
| Admitted | Allstate Indemnity Co. v. Dixon932 F.3d 696 | 8th Cir. 2019 | The Eighth Circuit affirmed admission of the insurer's fire experts in an arson-defense case, holding that NFPA 921 does not demand physical testing and that experts who observed the evidence and systematically included and excluded causes used a reliable method. |
| Exclusion reversed | Elosu v. Middlefork Ranch Inc.26 F.4th 1017 | 9th Cir. 2022 | The Ninth Circuit reversed the exclusion of the plaintiffs' fire investigator's cause opinion and the resulting summary judgment, holding that the trial court had weighed eyewitness accounts and demanded corroboration when Rule 702 asks only whether the opinion rests on a sufficient foundation. |
| Limited | United States v. Hernandez104 F.4th 755 | 10th Cir. 2024 | In an arson prosecution the district court admitted the government investigator's origin and accelerant opinions but excluded his opinions on separate points of origin, and the Tenth Circuit affirmed, holding that NFPA 921 is a flexible guide and that starting with witness interviews did not show expectation bias. |
Each case links to the free opinion text on CourtListener.
Under amended Rule 702
Since December 1, 2023, Rule 702 says expressly that the party offering an expert must show the court it is more likely than not that the testimony meets each requirement: that it rests on sufficient facts or data, uses reliable methods, and reflects a reliable application of those methods to the case. Questions about the basis of an opinion are no longer automatically matters of weight for the jury. For how the circuits have applied the amendment, see the Rule 702 tracker, which follows each court of appeals; for what that means for preparing or attacking this class of expert, see the guide on amended Rule 702.
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Last reviewed October 3, 2026. How this page is built: rulings are found by searching court opinions on CourtListener, and each one is read in the opinion before it is summarised here; outcomes are labelled by what the court did with the expert's testimony. No individual expert is named. This page summarises public decisions for orientation and is not legal advice; read the opinion before relying on any ruling.