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

Abstract

Forensic taphonomy as a discipline requires standardization to satisfy Daubert criteria for scientific data to be admissible in court. In response, there has been a shift towards quantification of methodology and estimating the post-mortem interval. Despite these advances, there are still biases and limitations within the discipline not explicitly addressed in the early stages of experimental design nor in final published works. In this article, unresolved debates with respect to the conductance and reporting of forensic taphonomic research are reviewed, beginning with the nature of experimental cadavers, human or animal analogues and their body size, and second, the forensic realism of experimental setups, specifically with respect to caging, clothing and number of carcases. Pigs, albeit imperfect, are a good model to gain a general idea of the trends that may be seen in humans in subsequent validation studies in facilities where human donors are available. To date, there is no consensus among taphonomists on the extent of the effect that body mass has on decomposition progression. More research is required with both human cadavers and non-human analogues that builds on our current knowledge of forensic taphonomy to answer these nagging questions. This will enable the discipline to make the reliable assumption that pigs and donor decomposition data can be applied to homicide cases. A suite of experimental design aspects is suggested to ensure systematic and standardized data collection across different biogeoclimatic circumstances to identify and quantify the effects of potential confounding variables. Such studies in multiple, varied biogeographic circumstances with standardized protocols, equipment and carrion will facilitate independent global validation of patterns. These factors are reviewed to show the need for adjustments in experimental design to ensure relevance and applicability of data within locally realistic forensic situations. The initiation of a global decomposition data network for forensic taphonomists is recommended. KEY POINTS Pigs are a valuable, albeit imperfect, proxy for human decomposition studies. There are few or conflicting data on effects of carcase size, carrion ecology, exclusion cages and scavengers. We recommend single, clothed, uncaged carcases for baseline research to reflect regionally specific forensic casework.

Human Bone Proteomes before and after Decomposition: Investigating the Effects of Biological Variation and Taphonomic Alteration on Bone Protein Profiles and the Implications for Forensic Proteomics

“…The sample size in this study reflects general trends in human decomposition research, in which larger sampleslike those used in clinical studiescan be difficult to obtain for practical, logistical, and ethical reasons. While animal analogues such as pigs can be used to alleviate some limitations associated with small sample sizes, the study of human cadavers is important due to biological differences between humans and pigs, including anatomical differences in the digestive vasculature and molecular differences in adipose tissue …”

“…While animal analogues such as pigs can be used to alleviate some limitations associated with small sample sizes, the study of human cadavers is important due to biological differences between humans and pigs, including anatomical differences in the digestive vasculature and molecular differences in adipose tissue. 36 Data on body decomposition and weather were collected throughout the experiment and can be found in Supporting Information (Table 1). Additional information on FARF's environment can be found in the Supporting Information.…”

Review of the current and potential use of biological and molecular methods for the estimation of the postmortem interval in animals and humans

“…Insects may also colonize the remains and assist in soft tissue decomposition. 11,69 The mineral matrix of ossified bones is resistant to degradation after death, and a fully decomposed body remains "skeletonized" for > 8-10 y. 19 In many cases, especially if foul play is suspected, estimating the PMI can be of central importance in establishing a chronology of events, including or excluding suspects and/or their alibis.…”

“…To date, no best method exists that accurately and reliably estimates the PMI. Extensive research has been published, 1,38,60,69,97,112 but only a few of the techniques described in the literature are sufficiently field-efficient to be applied for forensic purposes in human death investigations, 123 and even fewer are applicable in animal cases. 11 A realistic PMI is indirect and based on the time between when a person or animal was last seen alive and when the body was discovered.…”

“…11,21,90 Most of these studies conclude that further research and data are needed before being validated and declared field efficient; none of these techniques is currently used in forensic investigations. 69,120,123 Biological methods for estimation of the early PMI…”