646.1Fire/Arson Investigation

Last Updated: 12/01/23

Key Concepts

  • A properly qualified fire and arson investigator may testify as an expert witness on causation, point of origin, or the use of accelerants, and may opine whether the cause of the fire was natural, accidental, intentional, or undetermined.
  • Expert testimony in this field has traditionally been allowed in North Carolina.
  • Despite recent criticism of some of the techniques and principles involved in fire investigations, many courts applying the Daubert standard have continued to allow the testimony.


The Fire and Arson Investigation Unit of the North Carolina State Bureau of Investigation can assist in the investigation of fires and may classify the cause of a fire as: (i) natural; (ii) accidental; (iii) intentional; or (iv) undetermined. Investigators can use scent-detecting dogs and confirmatory lab testing to identify the presence of any accelerants that were used to start the fire, and may assist local law enforcement with investigating intentional fires. 

Fire and arson investigators may also rely on observations such as “burn pattern analysis,” in conjunction with known facts such as the building’s layout, construction materials, furnishings, and other factors to reach a conclusion about where and how a fire started, and whether a fire was intentionally set. This aspect of fire and arson investigation covers a wide variety of methods, techniques, and principles, each of which must be individually assessed on their own merits. Some of these investigative tools have recently faced criticism and questions about their scientific validity. For a concise summary of these issues – see Fire Investigation: A Plain Language Summary,” Charlie Hanger, Forensic Science Asssessments: A Qualilty and Gap Analysis, July 11, 2017.

Practice Pointer

But do any of those criticisms apply to this case?
It depends. For example, as noted in the study linked above, it can make a big difference whether a fire burned long enough and hot enough to reach the “flashover” point, which is the point where all combustible materials in the room ignite (i.e., changing from “a fire in a room” to “a room on fire”). Before flashover happens, identifying the origin of a fire is pretty straightforward; after flashover, it becomes much more difficult to pinpoint the origin.
The prosecutor should talk to the expert witness before trial in order to fully understand the particular methodology (and limitations) of the investigation that was performed in a given case. The prosecutor should then develop questions tailored to the expert’s experience and techniques. For general suggestions and guidance on structuring such questions, see the related entry on Expert Testimony – Generic Question Outline

Admissibility and Reliability

Expert testimony from an arson or fire investigator regarding his or her opinion on issues such as causation, point of origin, or the use of accelerants has traditionally been allowed in North Carolina courts. See, e.g., State v. Lassiter, 160 N.C. App. 443 (2003) (expert testimony that source of fire was a hydrocarbon fuel, and that it was impossible for ignited vegetable oil to have been source of fire, as claimed by defendant, and that fuel was poured in large quantity on home's floor, was admissible in trial for murder and fraudulently setting fire to a dwelling, despite defendant's claims that such opinion was mere speculation and that jury could form its own common sense conclusion about cooking fires); State v. Hales, 344 N.C. 419 (1996) (expert testimony that fire was started in an area where it was unlikely that gasoline would accidentally be spilled and then set on fire was admissible, despite the defendant’s claim that the opinion was mere speculation or lacked a factual basis); State v. Greime, 97 N.C. App. 409 (1990) (implicitly accepting as an expert a fire department lieutenant who was trained in arson investigation and routinely conducted arson investigations); State v. Miller, 61 N.C. App. 1 (1983) (witness properly allowed to give opinion testimony regarding fire investigation where defense counsel stipulated he was an expert in the field, based on his qualifications as a forensic chemist with eight years of experience doing fire investigation for the state, and witness’s testimony demonstrated that he was an expert in the field in which he was questioned); State v. Culpepper, 302 N.C. 179 (1981) (trial court erred in refusing to admit testimony of the defendant's expert witness that no accelerant was used to cause a fire when there was an adequate foundation for such expert testimony, and the prosecution's expert witness had previously testified that the fire was caused by the ignition of vapors from a flammable liquid poured on the floor).

North Carolina’s appellate courts have not yet clearly addressed whether this type of expert testimony is admissible under the amended version of Rule 702 that adopted the Daubert standard. The court in State v. Jeffries, 243 N.C. App. 455 (2015), allowed expert testimony on the issue of whether a fire was intentionally set, but that decision relied on case precedent and did not directly address Daubert or amended Rule 702. See also State v. Hunt, 250 N.C. App. 238 (2016) (declining to hold whether it was error to admit expert testimony by fire investigator without conducting a Daubert inquiry since it did not rise to plain error in light of other evidence of arson).

However, several federal courts have found this type of testimony reliable and admissible under Daubert. See, e.g., U.S. v. Aman, 748 F. Supp. 2d 531 (E.D. Va. 2010) (determining that expert testimony on origin and cause of fire was admissible under Daubert, and specifically addressing the 2009 NRC Report that criticized and questioned many of the theories and principles of arson investigations); accord U.S. v. Santiago, 202 Fed. Appx. 399 (11th Cir. 2006) (unpublished) (testimony of two fire investigators as expert witnesses was admissible under Daubert); U.S. v. Diaz, 300 F.3d 66 (1st Cir 2002) (witnesses were qualified to give expert testimony on causation of the fire); U.S. v. Gardner, 211 F.3d 1049 (7th Cir. 2000) (expert’s testimony “about the cause and origin of the fire, which helped the jury determine whether the fire was caused by arson” was admissible under Daubert and Rule 702); see also U.S. v. Quesada-Ramos, 429 Fed. Appx. 909 (11th Cir. 2011) (officer properly allowed to testify as expert regarding canine detection of accelerants in arson investigation).

Portions of this entry were excerpted from the North Carolina Superior Court Judges’ Benchbook, “Criminal Evidence: Expert Testimony,” Aug. 2017, Jessica Smith.