Post-mortem interval estimation in the tropical climate of Southern Nigeria

This study compared total body score (TBS) in buried remains (35 cm depth) with and without insect access prior to burial. Sixty rabbit carcasses were exhumed at 50 accumulated degree day (ADD) intervals. Weight loss, TBS, intra-abdominal decomposition, carcass/soil interface temperature, and below-carcass soil pH were recorded and analyzed. Results showed significant differences (p << 0.001) in decomposition rates between carcasses with and without insect access prior to burial. An approximately 30% enhanced decomposition rate with insects was observed. TBS was the most valid tool in postmortem interval (PMI) estimation. All other variables showed only weak relationships to decomposition stages, adding little value to PMI estimation. Although progress in estimating the PMI for surface remains has been made, no previous studies have accomplished this for buried remains. This study builds a framework to which further comparable studies can contribute, to produce predictive models for PMI estimation in buried human remains.

The rising homicide rates in Nigeria underscore the necessity for comprehensive post-mortem interval (PMI) estimations to enhance the reliability of forensic investigations. This study investigates the impact of Marabunta ants (Hymenoptera: Formicidae) on the decomposition process and PMI estimation in pig carcasses during the wet season in Okuku, Nigeria. Using two juvenile domestic pigs, we employed a controlled experimental approach at the Department of Anatomy and Forensic Anthropology Research Facility. The study spanned 30 days, with systematic observations of postmortem changes, insect activity and environmental conditions recorded at specified intervals. Results indicated pronounced effects of Marabunta ants on decomposition dynamics. Notably, the presence of these ants altered the expected insect succession patterns, delaying the colonisation by blowflies, which typically dominate the initial decay stages. By the second day, marked ant activity was observed, leading to distinct bite marks on the carcasses, while the other carcasses exhibited standard decomposition without any interference. Accumulated degree days (ADD) and total body scores (TBS) demonstrated a parabolic relationship, revealing rapid initial decay followed by a stabilisation phase as skeletonisation progressed. This research confirms that environmental conditions and insect activities significantly influence decomposition rates and PMI estimations. The findings suggest a need for forensic practitioners to recognise the role of Marabunta ants in decay processes and the potential misinterpretations of ant-induced marks as perimortem injuries. Future studies should explore seasonal variations in decomposition and insect succession to refine forensic entomological methodologies.

Inaccuracy of accumulated degree day models for estimating terrestrial post-mortem intervals in Cape Town, South Africa

Forensic taphonomy explores factors impacting human decomposition. This study investigated the effect of body mass on the rate and pattern of adult human decomposition. Nine males and three females aged 49-95years ranging in mass from 73 to 159kg who were donated to the Complex for Forensic Anthropology Research between December 2012 and September 2015 were included in this study. Kelvin accumulated degree days (KADD) were used to assess the thermal energy required for subjects to reach several total body score (TBS) thresholds: early decomposition (TBS ≥6.0), TBS ≥12.5, advanced decomposition (TBS ≥19.0), TBS ≥23.0, and skeletonization (TBS ≥27.0). Results indicate no significant correlation between body mass and KADD at any TBS threshold. Body mass accounted for up to 24.0% of variation in decomposition rate depending on stage, and minor differences in decomposition pattern were observed. Body mass likely has a minimal impact on postmortem interval estimation.

Retrospective analysis of factors affecting rate of skeletonization within a tropical climate

Postmortem interval (PMI) is very important in the crime scene investigation. However, it is very difficult to estimate of the interval since death after a decomposition. Recently, there have been various studies on the postmortem interval since a decomposition. In particular, the total body score (TBS) and accumulated degree days (ADD) used to estimate the postmortem interval after a decomposition. This study was conducted with the aim of applying the TBS and ADD to estimate the postmortem interval in real forensic caseworks. In first murder case, TBS was 12 and ADD value was 132, respectively. An estimated time of PMI was around 23:00 on June 21, and the suspect’s statement was 01:20 on June 22. Our estimated interval since death and the suspect’s statement for the PMI differ by only 2 hours and 20 minutes. In second forensic case, TBS was 3 and ADD value was 55, respectively, an estimated time of PMI was around 02:26 on September 23. The suspect’s statement was 10:30 on September 23. Our estimated time and the suspect’s statement for the PMI differ by 8 hours. In these cases, we were able to have confirmed the feasibility of TBS and ADD on the real forensic cases. Overall, our finding suggested that the quantitative method could be used to produce PMI estimates that are accurate to within days or even hours.

A eukaryotic community succession based method for postmortem interval (PMI) estimation of decomposing porcine remains

The decomposition process of corpse varies due to many factors. There are several studies conducted to improvethe postmortem interval (PMI) by visual inspection of human remains. In this study, a total body scoring methodwas developed to estimate the PMI based on the decomposition and degree days (DD). One hundred and threecases were used to estimate the PMI. The autopsy reports were scored using the decomposition scoring method. Thetemperature data was obtained from the Thailand Meteorology Department (TMD). The PMI was estimated usingthe total body score (TBS), accumulated degree day (ADD) and accumulated degree hour (ADH) from the findingdate back until the predicted time since death. To this end, a retroactive approach was taken in which cases from themedical examiner with a known “date last seen” and “date recovered” were compiled. A qualitative analysis wasconducted examining the specific decomposition changes which occur in various contexts. Quantitatively, a linearregression analysis was employed to determine if DD or TBS explained more of the variation in decomposition.The ADH, ADD and TBS were determined to be the main components in modelling decay. These results suggestthat the TBS can be optimally used to assess PMI. While the ADD and ADH were used to overestimate PMI, whichindicating inconsistency of the method. In total, a set of time since death estimation formula applicable to indoor,outdoor, and aquatic contexts was produced, and region-specific standards best suited to estimating time sincedeath in Thailand. Due to the subjectivity in all the available methods and decomposition is a highly variableprocess. Further research is required before an estimated PMI should be considered as evidence in court.

The objective of this study was to determine if a relationship between microbial neoformation of volatiles and the post-mortem interval (PMI) exists, and if the volatiles could be used as a tool to improve the precision of PMI estimation in decomposed human remains found in an indoor setting. Chromatograms from alcohol analysis (femoral vein blood) of 412 cases were retrospectively assessed for the presence of ethanol, N-propanol, 1-butanol, and acetaldehyde. The most common finding was acetaldehyde (83% of the cases), followed by ethanol (37%), N-propanol (21%), and 1-butanol (4%). A direct link between the volatiles and the PMI or the degree of decomposition was not observed. However, the decomposition had progressed faster in cases with microbial neoformation than in cases without signs of neoformation. Microbial neoformation may therefore act as an indicator of the decomposition rate within the early decomposition to bloating stages. This may be used in PMI estimation based on the total body score (TBS) and accumulated degree days (ADD) model, to potentially improve the model’s precision.

The effect of body size on the rate of decomposition in a temperate region of South Africa

Background and aim: Decomposition patterns and rates are important in forensic taphonomy for estimating postmortem interval and determining the hidden mode of death. The current research documents decomposition rates for four different modes of death using domestic pigs as proxies for human remains in Northern Cross River State, Nigeria. Methodology: Four porcine specimens were subjected to different modes of death (burning, strangulation, poison and blunt force trauma) and placed in open earth surface environment. Physical and chemical postmortem changes were monitored over 30 days, incorporating assessments of total body score (TBS), accumulated degree days (ADD), and insects colonization. Results: Distinct variations in the rates of decomposition between different modes of death. Fire-induced rapid early decomposition was observed among burnt carrion as a result of desiccation of tissues brought about by fire. The toxic environment probably brought about by insect mortality delayed decaying in poisoned carrion. Blunt trauma carrions decomposed more quickly than the strangulated and drowned specimens, while the environmental exposure accelerated tissue breakdown. Insects were a principal agent in the degradation of soft tissues, whose species diversity and activities differed between modes of death. Analyses of the soils demonstrated a modification of the physicochemical characteristics after decomposition fluids had acted, especially nitrogen enrichment, but were indicative of the importance of the role of soil in modulating decay rates. Conclusion: These findings present foundational insights into the advancement of forensic taphonomy and contribute to the enhancement of medico-legal investigations in Nigeria and other resource-constrained regions.

Given the multiple factors that may alter the rate of decomposition, one of the more difficult tasks that anthropologists and pathologists face is determining of the postmortem interval (PMI). While trauma has been widely accepted as being among those factors, recent published studies have contradicted this premise. However, major issues exist with these studies. Consequently, this study was designed to simulate a more realistic setting in an effort to settle this discrepancy in the literature. This study utilized eight porcine remains; three of which received incised wounds penetrating the thoracic cavity, three others received nonpenetrating wounds, and two were designated nontrauma controls. Measurements included evaluating the total body score (TBS) on temporal and accumulated degree days (ADD). Using a two-way repeated measures ANOVA, the results of this study found that while trauma does have an influence in the pattern of decomposition, it does not influence the rate of decomposition.

Estimating the postmortem interval (PMI) using accumulated degree-days (ADD) in a temperate region of South Africa

PurposeIn analyzing decomposing human remains in cases of unattended death, observing insect succession patterns to aid in estimating the post-mortem interval (PMI) based on carrion insects is one of the tasks of the forensic entomologist. The purpose of this study is to provide baseline data in order to improve PMI estimates using carrion insects. The lingering armed conflict in Nigeria creates a situation where unidentified human remains overwhelm law enforcement agencies. A common challenge is the lack of affordable, easy-to-use, and locally derived methods. This study aims to describe the succession patterns of arthropods, including insects, in pig carcasses in the wet and dry seasons in southern Nigeria as a baseline to aid in PMI estimation. Arthropods were observed and collected (all life cycle stages) in a total of 20 freshly-killed pigs (10 pigs for each season) which were deployed to study sites within 3 h of humane killing and at various times during the two seasons over 14 months. The time of appearance, activity, and disappearance of the arthropods were noted and related to the stages of decomposition to create succession patterns. Three classes, six orders, and 16 families of arthropods were collected. Musca domestica was the first to arrive, followed by Chrysomya marginalis, visiting within 10 min after placement. An ant species (Family Formicidae) had the widest presence through decomposition stages. There was an increase in the absolute number and species richness of arthropods in the wet season. Some arthropods, like the black soldier fly (Hermetia illucens), were exclusively present in the wet season. The observed succession patterns can be used as a reference for forensic scientists to aid in PMI assessment in Nigeria. Arthropods found exclusively in a season could be used to establish the season of death.

Comparing two scoring indexes for assessing decomposition of juvenile remains.