Section 18.2.5 states “[T]he elimination of all accidental causes to reach a conclusion that a fire was incendiary is a finding that can rarely be justified scientifically, using only physical data; however, the elimination of all causes other than the application of an open flame is a finding that may be justified in limited circumstances, where the area of origin is clearly defined and all other potential heat sources at the area of origin can be examined and credibly eliminated.” (Emphasis added.)
There are four essential criteria for the permitted use of the process of elimination in determining the cause of the fire.
1. The area of origin must be clearly defined and known conclusively to the exclusion of all other potential origins;
2. All accidental causes in the clearly defined area of origin must be examined and credibly eliminated;
3. The scientific method must be used in the analysis which eliminated all accidental causes and the remaining ignition source must be consistent with all known facts;
4. Whenever an investigator proposes the elimination of a particular system or appliance as the ignition source on the basis of appearance or visual observation, the investigator should be able to explain how the appearance or condition of that system or appliance would be different from what is observed, if that system or appliance were the ignition source for the fire.