The validation of 'universal' PMI methods for the estimation of time since death in temperate Australian climates

Forensic anthropologists have traditionally relied on their knowledge and experience of the decomposition stages to make an assessment of the time since death. However, recently new and empirical methods have been developed in various regions worldwide that propose to estimate the post-mortem interval (PMI) based on the observed decomposition changes alongside important taphonomic variables. Yet despite these methods being predominantly geographic specific, a number of methods have suggested they are effective universally and it is these 'universal' methods that have been inadequately test in Australia. The current study evaluated the accuracy of two of these methods in an Australian context, specifically the Greater Western Sydney region. The protocol developed by Megyesi et al. (2005) [1] was investigated because it is commonly cited in the literature and the PMI formula created by Vass (2011) [2] was also investigated because of its 'universal' claim. Between December 2014 and March 2016, two experimental trials were undertaken during the Australian summer seasons. Sixteen adult pig carcasses were left to decompose undisturbed on a soil surface common throughout the Western Sydney region and the Megyesi et al. (2005) [1] and Vass (2011) [2] methods were applied to the remains during this period. The results showed the Megyesi et al. (2005) [1] method overestimated the known PMI of remains, whereas the Vass (2011) [2] formula underestimated the time since death of the remains in these trials. The inaccuracy may be attributed to the constants which make up the variables in these formulas and they may not reflect the values of these variables in the Western Sydney region.