Estimating the post-mortem interval of skeletal remains: a taphonomic approach

Abstract

Determining the post-mortem interval (PMI) of human remains is integral to certain forensic investigations. Reliably estimating the PMI of skeletal remains within a forensic context has been demonstrated to be particularly difficult (Buchan and Anderson 2001; Cattaneo 2007). There is still no definitive way to accurately estimate the PMI of skeletal remains despite the publication of numerous methods. This study used a controlled animal model experiment conducted over 24 months between May 2012 and April 2014 in the Canberra region, Australia. Twenty-four fully fleshed Sus scrofa (White hybrid pigs) and 24 Macropus giganteus (eastern grey kangaroo) carcasses were placed on the ground surface at the fieldwork site. Twelve carcasses of each species had cages built around them, while the remaining twelve carcasses of each species were left uncaged. Every four months (120 days), four carcasses of each species were collected (two caged and two uncaged). All carcasses were recorded during the fieldwork to examine the effect of taphonomic variables such as local environment, invertebrate activity and bone weathering. The uncaged carcasses were additionally recorded during fieldwork for vertebrate scavenging activity, disarticulation and scattering.

Following the collection of carcasses at PMIs of 4, 8, 12, 16, 20 and 24 months, additional analyses were undertaken on the remains of the caged carcasses: including microscopic quantification of the bone surface; infra-red and Raman spectroscopy; and nano-indentation. Each analysis was conducted to examine the potential use of each in estimating the PMI from skeletal remains. The results demonstrated that using taphonomic variables, such as scavenging, disarticulation or bone weathering to estimate the PMI, was unfeasible due to the influence the local environment has on these variables. However, the quantification of the bone surface demonstrated there was an increase in quantity and size (area and diameter) of pores over the 24 month period. Furthermore, there was a measurable decrease in the CH-Aliphatic content over the 24 months when measuring using either an infra-red or Raman spectrometer. Show more