Fire pattern myths: an analysis of arson in Canadian courts

Prior to 1992, fire investigators generally examined fire scenes by subjective observation and a process of elimination. If no innocent cause could be determined, arson would be assumed. Arson was often concluded based on various fire pattern myths, for example, the belief that only the presence of an accelerant could result in “crazed glass” or spiderweb cracking. Such fire pattern myths were debunked in 1992 when NFPA 921 was published, disproving many myths and detailing the use of the scientific method. The present study was conducted to see whether fire pattern myths were still being mentioned in Canadian courts after 1992. Through a mixed methods study, 26 court case summaries ranging from 1979 to 2018 relating to arson were analyzed to identify the mention of fire pattern myths, negative corpus, placed accelerant or NFPA. Nine cases dated prior to and seventeen occurred after 1992. “Demarcation lines” and “multiple origins” in relation to accelerant placement were the most common and, were increasingly common after 1992.