A comparison of techniques for extracting ignitable liquid residue from concrete

Determining that a fire is the result of arson is a challenging task. Since many arsonists use some form of ignitable liquid, such as petrol, investigators may attempt to recover ignitable liquid residue (ILR) from a fire scene to help indicate if the fire was deliberately lit. Analysing debris for ILR can become difficult when debris cannot be transported to a laboratory for testing, such as when ILR is on a fixed concrete surface. Therefore, other techniques that are suitable for fieldwork must be considered. In this paper, four techniques for recovering ILR from a concrete surface are compared. The first three techniques involve covering the surface with an absorbent material: cat litter, absorbent matting or cotton pads. Each of these conditions requires an additional, laboratory-based extraction stage before it can be analysed for ILR. The fourth technique uses a new device that can perform the extraction procedure within the crime scene, thereby providing samples that are ready for analysis. This ne...