The combustion process requires the initial pyrolysis of materials to form characteristic degradation products in either a vapour or aerosol phase. The chemical composition of smoke will depend on, amongst other things, the particular fuels involved in the fire and the ventilation conditions within the fire compartment. Consequently, all fires can potentially produce a unique smoke “fingerprint”. Smoke will absorb easily onto clothing and will evaporate at a relatively slow rate; hence, if a suspect’s clothing can be seized within a few hours of exposure to smoke it may be possible to obtain the “smoke fingerprint” from the original fire.
The following data shows a good correlation between two items of clothing that had been exposed to the same smoke conditions:
When considering whether smoke odour analysis could be of use to an investigation, the following questions may assist in the decision-making process:
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What is the ultimate aim of the analysis? To provide a link between the suspect and scene, or quite simply to prove there is smoke on the suspect’s clothing?
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What were the materials first ignited? Do they differ greatly from the materials that were subsequently involved in the fire development?
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Was there anything unique about the smoke?
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Would the smoke from the fire have had time to adsorb onto the clothing of the person who set the fire?
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Does the suspect have a plausible reason for the presence of smoke on their clothing, and could the analysis assist in confirming or refuting their explanation?
Note that it is important to take comparison materials (of a similar composition to the suspect’s clothing) from the scene contemporaneously to the seizure of garments from the suspect. All items must be packaged in nylon bags with swan-neck seals.
Publication :
DeHaan, J.D., Brien, D.J., Large, R. “ Volatile Organic Compounds from the Combustion of Human and Animal Tissue ” Science & Justice 2004, Vol. 44(4), 223 – 236.
M-Scan Brochure: Biotechnology and Pharmaceutical Analysis (8pp.)