Peri-mortem disease treatment: a little known cause of error in the estimation of the time since death in decomposing human remains

A review of multi-disciplinary decomposition research and key drivers of variation in decay

The decomposition of animal remains is a multifaceted process, involving ecological, biological, and chemical interactions. While the complexity is acknowledged through concepts like the necrobiome, it's unclear if this complexity is reflected in research. Appreciation of the complexity of decomposition is crucial for identifying sources of variation in estimations of time since death in medico-legal science, as well as building broader ecological knowledge of the decomposition process. To gain insights into the extent of multidisciplinary research in the field of decomposition science, we conducted an examination of peer-reviewed literature on four key drivers of variation: volatile organic compounds, microbes, drugs/toxins, and insects. Among 650 articles, we identified their scientific discipline, driver/s of variation investigated, and year of publication. We found that 19% explored relationships between two drivers, while only 4% investigated interactions between three. None considered all four drivers. Over the past three decades, there has been a steady increase in decomposition research publications, signifying its growing importance. Most research (79%) was linked to forensic science, highlighting opportunities for interdisciplinary collaboration in decomposition science. Overall, our review underscores the need to incorporate multidisciplinary approaches and theory into contemporary decomposition research.

Bridging the gap between decomposition theory and forensic research on postmortem interval

Knowledge of the decomposition of vertebrate animals has advanced considerably in recent years and revealed complex interactions among biological and environmental factors that affect rates of decay. Yet this complexity remains to be fully incorporated into research or models of the postmortem interval (PMI). We suggest there is both opportunity and a need to use recent advances in decomposition theory to guide forensic research and its applications to understanding the PMI. Here we synthesise knowledge of the biological and environmental factors driving variation in decomposition and the acknowledged limitations among current models of the PMI. To guide improvement in this area, we introduce a conceptual framework that highlights the multiple interdependencies affecting decay rates throughout the decomposition process. Our framework reinforces the need for a multidisciplinary approach to PMI research, and calls for an adaptive research cycle that aims to reduce uncertainty in PMI estimates via experimentation, modelling, and validation.

Forensic experiments on animal scavenging: A systematic literature review on what we have and what we need

Vertebrate scavengers frequently affect forensic casework by feeding on human remains or by scattering body parts and bones. Therefore, animal activity can influence complete recovery of bodies, trauma analysis, and the estimation of the postmortem interval (PMI), potentially hampering identification of the deceased and elucidation of the perimortem circumstances. Experimental research is well suited to investigate scavengers and their impact on carcasses over time, generating knowledge on the forensic relevance of certain scavenger species or communities. However, there are currently no systematised standards to conduct these investigations with a forensic focus, impeding comparison and synthesis of the studies. In our work, we performed a systematic literature review and found 79 publications featuring terrestrial experiments on vertebrate scavenging and/or scattering within a forensic context. We extracted 21 variables describing the study environment, experimental design and the specimens. The results show that there is considerable inconsistency in the study designs and that some of the variables are insufficiently reported. We point out research questions and areas that require attention in future studies, stressing the importance of infrequently mentioned or applied variables. Furthermore, we recommend guidelines to include and report a list of variables in forensic scavenging and scattering experiments. These guidelines will help standardising future research in the field, facilitating inter-study consolidation of results and conclusions, and consequently, inform forensic casework.

Field succession studies and casework can help to identify forensically useful Diptera

Fly development rates, and to a lesser extent succession data, can be used to provide an estimate of a minimum postmortem interval (mPMI). Yet, these data are most useful when a full account of species' ecology, seasonality, and distribution is known. We conducted succession experiments on human cadavers over different seasons near Sydney, Australia, to document forensically useful information, including the pre-appearance interval for carrion flies. We also compiled a detailed record of flies identified in casework collected in 156 cases distributed across New South Wales, Australia. We then compared the occurrence of fly species from both field and casework datasets to identify any consistencies or gaps to determine how useful species might be for forensic investigations. In the field experiments, we found differences in species diversity and abundance between seasons, as well as yearly variation between two winter seasons. Most fly species we recorded ovipositing showed a 2- or 3-day delay between adult arrival and oviposition in summer, with a longer delay in winter. Species that were previously encountered in casework, such as Calliphora augur (Fabricius, 1775) and Calliphora ochracea Schiner, 1868, were confirmed as forensically useful, with their colonization behavior and seasonal preferences documented here. Although not encountered in casework, we confirmed Hemipyrellia fergusoni Patton, 1925 as a primary colonizer of human cadavers. Our study emphasizes the need to link field and casework data for a complete understanding of all aspects of a carrion fly's ecology to assist forensic investigators in mPMI estimations.

Histological quantification of decomposed human livers: a potential aid for estimation of the post-mortem interval?

The objective of this study was to determine if a novel scoring-based model for histological quantification of decomposed human livers could improve the precision of post-mortem interval (PMI) estimation for bodies from an indoor setting. The hepatic decomposition score (HDS) system created consists of five liver scores (HDS markers): cell nuclei and cell structure of hepatocytes, bile ducts, portal triad, and architecture. A total of 236 forensic autopsy cases were divided into a training dataset (n = 158) and a validation dataset (n = 78). All cases were also scored using the total body score (TBS) method. We specified a stochastic relationship between the log-transformed accumulated degree-days (log₁₀ADD) and the taphonomic findings, using a multivariate regression model to compute the likelihood function. Three models were applied, based on (i) five HDS markers, (ii) three partial body scores (head, trunk, limbs), or (iii) a combination of the two. The predicted log₁₀ADD was compared with the true log₁₀ADD for each case. The fitted models performed equally well in the training dataset and the validation dataset. The model comprising both scoring methods had somewhat better precision than either method separately. Our results indicated that the HDS system was statistically robust. Combining the HDS markers with the partial body scores resulted in a better representation of the decomposition process and might improve PMI estimation of decomposed human remains.

Effects of peri-mortem infection on the entomofauna of decomposing buried human remains - a metadata analysis

The role of infectious disease as a cause of death is undeniable. The affect infectious disease may have on decomposition after death is less well established. Furthermore, virtually no information is available regarding the effects of burial conditions in such circumstances, despite that numerous clandestine burials occur each year. Although many aspects of post-mortem pathology are well understood and provide frequent insight in medicolegal investigation, where buried bodies are concerned, there is great variation in the decomposition processes, depending on extrinsic and intrinsic conditions. Criminal burials and hurriedly dug clandestine graves are seldom deeper than 120 cm allowing access to certain invertebrates, excluding others that only develop in unburied bodies. Numerous studies have reported on such clandestine graves with a purpose to facilitate forensic investigation, but our knowledge of decomposition in deeper graves lags behind, despite several often-cited papers of over a century ago. The poor level of detail in deep-grave knowledge is in part due to resource deficiencies and ethical considerations, but in part due to lack of thorough investigation of the data in papers of often cited prior work. To this end, a metadata analysis assessed a paper written by Dr. Murray Galt Motter in 1898, providing detail of 150 disinterment events with linked medical records from City of Washington cemeteries. This paper, written more than a hundred years ago, was largely descriptive and the detailed data provided in a summary table were never fully analysed. The paper is often quoted despite these obvious oversights. The present study revisits this work, applying a frequency statistical analysis conducted using categorical data and chi-squared analysis. This new analysis reveals patterns and relationships so long 'locked-up' within the body of the table and provides greater understanding of the effect of infectious disease on the abundance of species in the entomofauna associated with deeply buried remains. The data confirm that the presence of adipocere (saponification) is detrimental to development of soil entomofauna ((X² = 6·64, df = 1, p < 0·01)). Some species, in particular Proisotoma sepulcralis (Collembola), Eleusis pallida (Coleoptera) and Conicera tibialis (Diptera), were positively influenced by association with infectious disease cases (p < 0·01) while only Piophila casei (Diptera) demonstrated a negative association (p < 0·05). Furthermore, the presence of peri-mortem infectious disease, while not necessarily a cause of death, influences post-mortem colonisation of the buried body by insects. The abundance of some species is enhanced, suggesting that bacterial burdens enhance decomposition in a manner favourable to insect feeding and hence abundance, by releasing compounds that the entomofauna feeds on.

Differential Scavenging Among Pig, Rabbit, and Human Subjects

Different animal species have been used as proxies for human remains in decomposition studies for decades, although few studies have sought to validate their use in research aimed at estimating the postmortem interval. This study examines 45 pig, rabbit, and human subjects placed in three seasonal trials at the Anthropology Research Facility. In an earlier paper, we found that overall decomposition trends did vary between species that could be due to differential insect and scavenger behavior. This study specifically examines if scavenger behavior differs by carrion species. Daily photographs, game camera photographs, written observations, and Total Body Score (TBS) documented scavenging and decomposition changes. Results show that raccoons were the most commonly observed vertebrate scavenger, that scavenging was most extensive in winter, and that certain human subjects were preferred over other humans and all non-human subjects. Finally, scavenging activity greatly reduces the accuracy of postmortem interval estimates based on TBS.

Analysis of the Effect of Cyclophosphamide and Methotrexate on Chrysomya megacephala (Diptera: Calliphoridae)

Forensic entomotoxicology investigates the effects of chemical substances in the development of scavenger insects and the reflection on estimating the minimum postmortem interval (PMI). To evaluate the impact of the chemotherapeutic drugs cyclophosphamide (CF) and methotrexate (MTX) on the postembryonic development of Chrysomya megacephala, controlled experiments were performed by rearing the larvae on spiked minced beef with different concentrations of these drugs. The results indicated that CF significantly decreased their developmental rate up to 28 h but had no significant effect on larval and adult sizes, survival rate, and sex ratio, whereas MTX decreased larval and adult sizes, survival rate, and there was a deviation in the expected sex ratio toward females in MTX-exposed larvae but had no significant impact on developmental rate. These negative interference factors should be considered in cases of suspected death of people that have undergone chemotherapy.

Critical issues in the historical and contemporary development of forensic anthropology in Australia: An international comparison

The aim of this brief critical qualitative analysis is to examine the development of forensic anthropology in Australia, at a time of significant change in the discipline. It will briefly summarise its historical establishment, making comparative reference to other regions-particularly the United Kingdom and United States, and the influence of the Bali Bombings of 2002, Indian Ocean earthquake and tsunami of 2004 and Black Saturday Bushfires of 2009. The analysis goes on to consider key factors in research in forensic anthropology in the United States, and the development of standards and regulation in the US and UK. The significance of research in post-mortem diagenesis in Brazil-a country sharing aspects of climate, soil types and demography with Australia-is also considered, as well as the significance of patterns of casework encountered in Australia compared with those of other jurisdictions. While forensic anthropology as a discipline has grown remarkably in recent years, this analysis suggests that research and training tailored to the specific pattern of casework encountered in Australia is now essential to support the development of national standards in science, education, and professional regulation. The significance of the establishment of the first taphonomy research facility outside of the US-the Australian Facility for Taphonomic Experimental Research-is briefly considered with reference to what this facility may offer to the development of forensic anthropology in Australia.