Fire examiners have been opining about the cause of fires for years. Often they are employed primarily by insurance companies.

How can they tell if a fire was caused by arson? For years, fire investigators were taught to look for key "indicators." Crazed glass, melted copper wiring, and melted steel were all said to indicate an unusually hot fire, consistent with the use of accelerants. Uneven burn patterns were said to reflect multiple ignition points, another indicator of arson. This conventional wisdom of fire investigation appears in textbooks and provided a "scientific" basis for expert testimony in thousands of cases.

More recent research suggests that much of the conventional wisdom of fire investigators is simply wrong. An analysis of 50 homes burned the 1991 Oakland Hills fire (a wild fire) showed a high frequency of traditional "arson indicators" where arson clearly had not occurred (Lentini, 1992). Fire investigators failed to realized the error in their conventional wisdom because there have been few careful, empirical studies of the results of "naturally occurring" fires. All of which raises serious questions about which opinions (if any) of fire investigators should be treated as "scientific knowledge."