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The mythology of arson investigation

Unlike in many other fields of scientific inquiry, progress in fire investigation is held back by the burden of an entrenched mythology. Despite the fact that it has been fifteen years since NFPA 921 was first published, some fire investigators still rely on “misconceptions” about the meaning of various fire effects and fire patterns. This paper will explore the development and promulgation of the mythology of arson investigation. Certainly, there is no reason to believe that anyone ever set out to promulgate something that was not true. It is likely that many myths came about as a result of unwarranted generalizations. For example, an investigator might observe a pattern of spalling around the remains of a gasoline container and make an association of gasoline with spalling. The next time that spalling is observed, gasoline is inferred. Some myths arose because of intuitively “obvious deductions.” The notion that gasoline burns hotter than wood is an appealing one, as is the notion that a narrow V-pattern indicates a “rapid fire.” The problem is that the term “rapid” is never defined, thus making it impossible, in many cases, to actually design an experiment to test a particular hypothesis about the significance of a particular indicator. Even when an indicator can be shown by direct evidence to be of no value, resistance to change and a culture of “circular citations” allow the myth to live on. Many of the myths were gathered by the Law Enforcement Assistance Administration (LEAA) and published in Arson and Arson Investigation Survey and Assessment (1977), and although they were reported with appropriate cautionary language, the cautions were not heeded. And when the “indicators” were listed by what should have been the ultimate authority, the cautions were lost. No less an authority than the National Bureau of Standards (NBS then—now NIST) published a Fire Investigation Handbook (1980), which stated that crazed glass meant rapid heating, shiny alligator blisters meant that a fire burned “faster than normal,” and narrow V’s indicate “fast-developing, hot fires.” In the 1980s, one American text after another referred to the NBS publication or to another publication that cited the myths published in the LEAA report. These circular citations continue in books still in print. Interestingly, many of the myths never gained much credibility in the United Kingdom because the major “go to” textbook, Cooke and Ide’s a This paper is essentially a distillation of Chapter 8 from the author’s textbook, Scientific Protocols for Fire Investigation, CRC Press, 2006.