Negative Corpus

NFPA 921 | Law Review ArticlesResearch ArticlesCases

Negative corpus is the process of determining what caused a fire by eliminating each possible cause, one by one, until only one possible cause remains.  The one remaining possibility is then determined to be the cause of the fire, regardless of a complete lack of physical evidence to support that conclusion.

Even though the most recent editions of NFPA 921 have soundly rejected negative corpus as a violation of the scientific method, it continues to be applied by fire investigators to draw expert conclusions based on an absence of evidence.

NFPA 921

NFPA 921 (2014), 19.6.5, at 203
The process of elimination is an integral part of the scientific method. Alternative hypotheses should be considered and challenged against the facts. Elimination of a testable hypothesis by disproving the hypothesis with reliable evidence is a fundamental part of the scientific method. However, the process of elimination can be used inappropriately The process of determining the ignition source for a fire, by eliminating all ignition sources found, known, or believed to have been present in the area of origin, and then claiming such methodology is proof of an ignition source for which there is no supporting evidence of its existence, is referred to by some investigators as negative corpus. . . [Negative corpus] is not consistent with the scientific method, is inappropriate, and should not be used because it generates untestable hypotheses, and may result in incorrect determinations of the ignition source and first fuel ignited.  Any hypotheses formulated for eh casual factors (e.g., first fuel, ignition source, and ignition sequence), must be based on the analysis of facts.  Those facts are derived from evidence, observations, calculations, experiments, and the laws of science.  Speculative information cannot be included in the analysis.

NFPA 921 (2014), 19.4.4.3, at 202
There are times when there is no physical evidence of the ignition source found at the origin, but where an ignition sequence can logically be inferred using other data. Any determinations of fire cause should be based on evidence rather than on the absence of evidence; however, there are limited circumstances when the ignition source cannot be identified, but the ignition sequence can logically be inferred. This inference may be arrived at through the testing of alternate hypotheses involving potential ignition sequence, provide that the conclusion regarding the remaining ignition sequence is consistent with all known facts. The following are examples of situation that lend themselves to formulating an ignition scenario when the ignition source is not found during the examination of the fire scene. This list is not exclusive and the fire investigator is cautioned to to hypothesize and igniting sequence without data to logically supports the hypothesis.

(A) Diffuse fuel explosions and flash fires.

(B) When an ignitable liquid residue (confirmed by laboratory analysis) is found at one of more locations within the fire scene and its presence at the location(s) does not have an innocent explanation.

(C) When there are multiple fires.

(D) When trailers are observed.

(E) The fire was observed or recorded at or near the time of inception or before it spread to a secondary fuel.

Law Review Articles

Folklore and Forensics: The Challenges of Arson Investigation and Innocence Claims, P. Tafti and P. Bieber, 119 W. Va. L. Rev. 549 (2016)

Research Articles

None at this time

Cases

State of Wisconsin v. Joseph A. Awe, Case No. 07 CF 54 (Decision and Order, State of Wisconsin, Circuit Court, Marquette County, 3/21/2013).

Jeffrey Russ v. Safeco Insurance Company of America, No. 2:11CV195-KS-MTP, 2013 WL 1310501 (S.D. Miss. 2013)

State of Arizona v. Robert Douglas Gibson Jr., CR20104390-001 (Ruling of Hon. Paul E. Tang, July 25, 2013).