Characterization of background and pyrolysis products that may interfere with the forensic analysis of fire debris

Abstract

An important aspect of an investigation of a suspected arson case involves the chemical analysis of the debris remaining after the fire. Forensic chemists apply the tools of analytical chemistry for the extraction, isolation and analysis of the target compounds that characterize ignitable liquid residues (ILR). Complex organic mixtures such as automobile gasoline, diesel fuel and other volatile mixtures that could be used to accelerate an intentionally set fire are routinely identified in forensic laboratories. The presence of these target compounds suggests the presence of ILR originating from these mixtures and this information could aid a fire investigator in determining the cause of the fire, including whether or not arson is suspected. The current study aims to characterize the background and pyrolysis products resulting from controlled burns of materials commonly found in homes and businesses in order to determine their chemical composition. A list of compounds found from the pyrolysis (and combustion) of different substrate types is compared with the target compound list for the identification of ILR. The results show that the burning of some types of commonly found materials creates some of the target compounds commonly found in ILR mixtures. The sources of these compounds are: substrate background products (in the substrate matrix prior to burning), pyrolysis products and, possibly, combustion products.