Forensic evidence in the decomposition of animal carcasses: use of entomology and stable isotopes

Abstract

The use of insects as forensic evidence is a typical tool in criminal investigations. Among other applications, the succession patterns of these organisms are used to infer the time when the remains are decomposing. More recently, the use of stable isotopes in forensic science has been intensifying through numerous applications. In isotopic ecology, ´13C is used to trace food sources and calculate their proportion in the organisms' diet, while ´15N is an indicator of the trophic level of organisms. Thus, the use of necrophagous arthropods and their isotopic signatures could reveal their development in human or animal tissue. That can be a promising way of attributing such entomological samples from a crime scene to a particular food source and, eventually, can be extended a possible post-mortem interval. Forensic entomology and forensic isotopy are well documented. However, few works associate entomology and isotopes within the forensic sciences. The main objective of this work is to study the decomposition of carcasses and the succession of necrophagous insects in an attempt to associate the isotopic variation with the post-mortem period. Field experiments will be carried out in two campaigns where animal substrates will be placed for decomposition (stillborn pigs). In the laboratory experiment, some species of scavenger insects and stillborn pigs' organs will be selected for oviposition. Will be sampled insects associated with the carcasses and substrate. Environmental parameters (temperature and humidity) will also be measured. The organisms and substrates will be submitted to isotopic analysis. Finally, the future results of this study should contribute with new information or solidification of concepts about isotopic variation along carcass decomposition and a post-mortem period, turnover, and isotopic fractionation in terrestrial insects, among other possible findings.