A comparison of human and pig decomposition rates and odour profiles in an Australian environment

Abstract

Cadaver-detection dogs are trained to locate victim remains; however, their training is 5 challenging due to limited access to human remains. Animal analogues, such as pigs, are 6 typically used as alternative training aids. This project aimed to compare the visual 7 decomposition and volatile organic compound (VOC) profile of human and pig remains in an 8 Australian environment, to determine the suitability of pig remains as human odour 9 analogues for cadaver-detection dog training. Four human cadavers and four pig carcasses 10 were placed in an outdoor environment at the Australian Facility for Taphonomic 11 Experimental Research (AFTER) across two seasons. Decomposition was monitored 12 progressively in summer and winter. VOCs were collected onto sorbent tubes and analysed 13 using comprehensive two-dimensional gas chromatography-time-of-flight mass 14 spectrometry. Visual observations highlighted the differences in decomposition rates, with 15 pig remains progressing through all stages of decomposition, and human remains undergoing 16 differential decomposition and mummification. Chemical and statistical analysis highlighted 17 variations in the composition and abundance of VOCs over time between the odour profiles. 18 This study concluded that the visual decomposition and VOC profile of pig and human 19 remains was dissimilar. However, in cooler conditions the results from each species became 20 more comparable, especially during the early stages of decomposition.

Why does the UK need a Human Taphonomy Facility?

“…It is dangerous to assume that results and experience gained from animal experiments can be applied to human bodies. The fact that differences in the decomposition process between human and pigs have been found (Connor et al, 2017, Dautartas et al, 2018, Knobel et al, 2018, should worry all forensic scientists, and indeed all those working in the criminal justice sector. These findings can only come from institutions that have the ability to compare human and animal decomposition, but is it important that further research occurs on this topic.…”

“…All of the test animals decomposed at different rates, with pig cadavers decomposing faster than humans on average; and there was more inter-individual variation in the humans than between the rabbits or pigs. A 2012 study in Texas also found differences in scavenging between animal and donated human cadavers (Rippley et al, 2016;Knobel et al, 2018). These differences suggest that animal carcasses not suitable as analogues for human remains (Duatartas et al, 2018;Connor et al, 2017;Stokes et al, 2013;Knobel et al, 2018;Alapo, 2016).…”

“…The scope of this research necessarily includes many sciences related to forensic science, such as geology and geophysics, archaeology, environmental science, ecology, botany, pathology and medicine, and analytical chemistry, for example. Current research at AFTER is monitoring how facial tissue thicknesses change with post-mortem interval (Stuzner, 2016), as well as volatile organic compound release from cadavers (Luong et al, 2018;Knobel et al, 2018). In addition, research has also started on the detection of clandestine and mass graves through the use of LiDAR scanning, hyperspectral imagery, infra-red photography and drone imaging (Blau, 2017).…”

“…Occasionally, extracted human teeth may be used (Irish, 2018). Otherwise, HRD dogs are trained using animal analogues for humans, usually porcine carcasses (Knobel et al, 2018), and yet are expected to consistently find human remains operationally (Irish, 2018). Recently, comparative analyses of VOCs produced during human and pig decomposition have been conducted at AFTER (Stadler et al, 2013;Stokes et al, 2013) that show that there are differences between them in terms of ratio and abundance of VOCs, resulting in differing odour profiles (Cablk et al, 2012).…”

A review of experimental design in forensic taphonomy: moving towards forensic realism

“…A more recent entomological study from Australia used both humans and pigs to compare decomposition rates and odour profiles for training cadaver-detection dogs [ 23 ]. They found that pigs decomposed differently and more quickly than humans.…”