Characterisation of background and pyrolysis products that may interfere with forensic analysis of fire debris in Mauritius

Abstract

Petrol is one of the most commonly used liquid accelerants in arson cases. It is identified by the presence of an abundance of aromatic compounds whose peaks cluster in specific patterns. The positive identification of these target compounds suggests the presence of the petrol in the debris. This information can assist a fire investigator in determining the cause of the fire, including whether or not arson is suspected. The current research aims at studying the legitimate background products in fire debris, including their identification and characterisation. A range of substrates commonly encountered at fire scenes in Mauritius were analysed in the presence and absence of petrol using the passive headspace absorption method. In unburnt samples, a number of interfering products were identified and some of the hydrocarbons liberated were those commonly found in petrol. When comparing the results of the burnt with the unburnt samples, it was found that only a small proportion of the volatiles detected in the burnt items were due to pyrolytic products and the rest were attributed to residues originally present in the unburnt items. Samples analysed in the presence of petrol, revealed that the concentration of these interfering products were below the detection limit for the accelerant and thus did not cause misinterpretation of the data.