## 1 Introduction  
During cadaver decomposition a variety of chemical and biological processes contribute to the evolution of odorous chemicals known as volatile organic compounds (VOCs). The resulting decomposition VOC profile has important implications in the search and recovery of victims and in subsequent post-mortem interval (PMI) determination. Forensic search procedures for missing persons or victims of homicide employ the use of detection dogs [1, 2, 3, 4] or handheld detection devices [5, 6, 7, 8] that rely on decomposition VOC recognition. These can also be used in disaster victim recovery where speed and accuracy are paramount concerns [6, 8]. VOCs released during decomposition attract a predictable pattern of arthropods (referred to as insect succession) to deceased victims, which can further be used to estimate PMI in forensic casework [9, 10]. These areas of forensic practice rely on the production of volatile organic compounds from a victim. Thus, establishing an accurate decomposition VOC profile can provide information for improving best practices. Decomposition odour research over the past ten years has elucidated key consistencies in the decomposition VOC profile. These trends have been well-documented in [1, 3, 4, 5, 6, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]. Inconsistencies exist in the VOC profiles reported in published literature, which reflects variations in decomposition variables (environment, weather, soil type, cadaver/carcass size, geographical location _etc._) and/or analytical methods (collection technique, instrument used, instrument parameters, _etc._) used in these studies. Variation-inducing factors are often associated with outdoor decomposition environments involving soil. Leached decomposition by-products entering soil exhibit different retention based on soil characteristics such as temperature, texture, moisture and humidity [4]. Soil can be thought of as a sink for VOCs where a chemical can coexist in a liquid state between soil particles, as a vapour in the soil gas, or as a solid sorbed onto soil particles [21]. In addition, leached nutrients can impact components of the soil community such as microorganisms. Soil organisms produce volatile metabolic by-products that can be released into the soil thereby further impacting the soil's VOC profile [5]. Decomposition VOCs released directly into the atmosphere from decomposed remains have been considered previously in the literature [1, 6, 14, 15, 16, 17, 18, 19, 20, 22]; however there are few studies that have investigated the VOC profile from the soil beneath decomposing remains. A range of collection techniques, conditions, and instrumentation have been used in decomposition soil VOC studies. Both [PERSON] [4] and [PERSON] _et al._[11] identified a reduced number of VOCs compared to traditional decomposition VOC studies that investigated the headspace above remains. However, [PERSON] and [PERSON] [22] showed that a direct comparison between headspace and soil from the same remains demonstrated additional compounds in the soil. The decomposition process changes over time resulting in a dynamic VOC profile. Trends in VOC evolution during early decomposition (days or weeks) differ from trends in later decomposition (months or years). While longitudinal VOC studies have been reported for the headspace above decomposed remains, this has not been a focus for decomposition soil analysis. Longitudinal analysis involves the repeated measurement of a response over a period of time. Without longitudinal measurements the dynamicity of VOC production and soil interactions are not portrayed because components of the profile may not be present at the chosen point of analysis. This may reveal the cause for some studies citing a reduced decomposition VOC presence in soils [4, 11]. Collection techniques used for decomposition VOCs also impact the number and types of VOCs captured and detected.