Abstract:

Fire is one of the most common disasters threatening public safety and social development; arson, a typical violent crime, is a serious threat to people's lives and property. Suspects are likely to use accelerants to commit effective and rapid arson. Therefore, the identification of accelerants is of crucial importance in determining the nature of a fire. Fires are commonly complex and intricate, leading to remarkable interference in accelerant identification. During the development of a fire, thermal environment influences the preformed accelerant combustion residues, causing the characteristic components of the accelerant to volatilize/pyrolyze to different degrees, thus interfering with accelerant identification. There are numerous petrochemicals with characteristic components similar to those of accelerants in fire scenes, also contributing to the interference in the determination of the presence of accelerants. After the fire is extinguished, the combustion residues of the accelerant in the fire scene are influenced by the combined effects of heat, light, and pressure in the ambient environment, resulting in the loss of the mass fraction of characteristic components, mainly in the form of volatilization. In particular, with countless microorganisms in the soil, the characteristic components of the present accelerants are degraded, resulting in the reduction or absence of some components, which seriously influences the accuracy of accelerant identification. This study describes the progress of research on the interference in accelerant identification induced by various factors at fire scenes from four aspects: thermal environment, matrix interference, weathering effect, and microbial degradation, with emphasis on the interference from the first aspect. Based on the correlation between the matrix chemical composition/structure and interference degree, new results pertaining to the interference source in accelerant identification are also considered. The shortcomings of current research and the prospects for future research are put forward to provide a reference for accelerant identification at fire scenes. Many studies have been conducted on the above four types of interference in recent years, which provide important reference for accelerant identification regarding the arson caused by ignitable liquids. However, with the application of new materials and techniques, fire scenes have become increasingly complex, which demands higher requirements for accelerant identification in forensic science. Research on thermal environment interference is still in its infancy, and it is of great practical significance to conduct this research on other types of accelerants coupled with other interference factors. In addition, the principle of most of the current research on selecting objects is based on common appearance at fire scenes, rather than the functional group of the chemical structure of the matrix. Systematic and in-depth research on the interference law and mechanism is urgently required, and it is vital to further explore the interference law of the fire background from the perspective of the chemical composition and chemical structure of the substrate. Compared to foreign countries, there is less research on the interference of weathering and microbial effects on ignitable liquid identification in China. Most importantly, there is a lack of unified provisions, such as standard experimental methods to carry out such research, making it urgent to establish relevant standards and specifications. Additionally, while weathering is caused by multiple factors, the existing research on the interference of the weathering effect with ignitable liquid identification focuses merely on volatilization. Therefore, a more accurate experimental design is necessary. Improving the database of interferents under fire conditions, and combining the application of the chemometrics method for the artificial intelligence identification of the combustion residue spectrum, is an effective way to further improve the identification efficiency and accuracy.

Key words: fire investigation, accelerant, identification, interference, review