Informing regional taphonomy research using retrospective forensic anthropology cases in the Western Cape, South Africa

Long-term qualitative analysis of clothing degradation associated with surface-decomposition in Cape Town, South Africa

The effect of clothing on the decomposition process of human and non-human animal bodies has received considerable attention. Yet, little attention has been given to the effect of decomposing bodies on the integrity of carrion-associated clothing globally, with no data from Africa. We conducted a long-term (over three years) micro- and macroscopic qualitative analysis of the degradation of synthetic, natural, and mixed-fiber clothing associated with surface-decomposing porcine bodies in Cape Town, South Africa. Five porcine bodies dressed in seasonally appropriate clothing were surface deployed and allowed to decompose over multiple seasons in the thicketed Cape Flats Dune Strandveld, an environment of forensic interest in Cape Town. Microscopically, the yarns of synthetic (acrylic pullover jerseys), natural (cotton T-shirts), and mixed-fiber (denim jeans) clothing were distorted and degraded within two to six months, one to three months, and one and a half to two years, respectively. Macroscopically, synthetic, and mixed-fiber clothing showed no visible damage after three years and ten months. Conversely, damage in the form of multiple small holes was noticeable on the natural fiber clothing within two to seven months, with complete disintegration of the clothing evident within two and a half years or less. This study is the first to elucidate the degradation of clothing associated with surface-decomposing bodies in Africa. Our findings reveal that the yarns of synthetic, natural, and mixed-fiber clothing associated with surface-decomposing bodies will degrade over time in different ways and can be used as indicators of the minimum time-since-death of clothed deceased individuals.

Terrain of taphonomy: how biogeographic variation affects decomposition and scavenger behaviour in two forensically significant habitats of Cape Town, South Africa

In South Africa, high rates of unidentified human remains necessitate the establishment of regionally specific high resolution taphonomic data to facilitate accurate reconstruction of postmortem circumstances and timing, as well as identification. This study investigates the effects scavenging and environmental conditions on the decomposition process using porcine models as human analogs across two distinct forensic sites in Cape Town: a suburban site and a peri-urban site. Over four deployments (July 2021-January 2023), six clothed porcine bodies were placed at each site and monitored. Data collected included mass loss, scavenger activity (notably by the Cape grey mongoose Galerella pulverulenta), and environmental variables. Findings revealed that seasonal variations and habitat types had significant impacts on the rate and pattern of decomposition. Porcine bodies at the Medical Research Council site consistently decomposed faster than those at the University of Cape Town site due to the micro habitat differences documented between the two sites. This research underscores the importance of considering biogeographic variation and the displacement of vertebrate scavengers in urban settings, emphasising the need for careful site selection in decomposition research to better reflect some forensic urban scenarios. By replicating the locally prevalent medicolegal death scenario of a single clothed body, the study enhances understanding of postmortem processes in Cape Town and contributes to the refinement of methodologies for forensic taphonomy within specific ecological contexts.

Retrospective review of forensic entomology casework in eastern Australia from 1994 to 2022

Forensic entomology can be a crucial source of information for medicolegal investigations, with its most well-known application being for estimating minimum post-mortem interval (mPMI) in death investigations. The analysis of entomological evidence requires robust data on insect ecology, life history, behaviour, and taxonomy. In Australia, substantial basic research on forensically relevant insects has focused predominately in the populous southeast and southwest; however, knowledge gaps remain, most importantly for the tropical north. In addition, there are scant casework data available publicly, which limits the ability of practitioners to make connections between fundamental research and real-world casework and hampers refinement of analytical methods and techniques. To address this gap, this project collated and analysed data from expert forensic entomological casework reports for five eastern Australia jurisdictions (South Australia, Victoria, New South Wales, Australian Capital Territory and Queensland) for a period spanning nearly thirty years (1994-2022). Relevant data extracted from casework reports included species and life stages collected, various decedent and case characteristics, type of opinion requested and estimated mPMI. These data were used to explore associations between species composition and geographical region, surrounding environment, season, and decedent characteristics (e.g., wounds). Additionally, the accuracy and investigative 'value' of mPMI estimates was assessed, which demonstrated that entomology-derived timeframes are largely reliable and highly informative. Finally, we report the first records in Australian casework for several species and highlight several areas that require additional research to fill critical gaps in our knowledge. Overall, this review represents highly practical real-world data that will be of enduring benefit to the forensic community.

A consolidated summary of South African human skeletal repositories

AIM

Human skeletal repositories are crucial resources for research and education in human biology, variation, anatomy, biocultural frameworks, forensic/medico-legal casework, heritage and understanding the past. In this review paper, we assess the composition of human skeletal repositories in South Africa, along with the ethical and legal frameworks that safeguard their curation.

METHODS

The data and information pertaining to local human skeletal repositories were gathered through a combination of literature review and direct contact with local curators for information. Data pertaining to source origins, sample demographics, and temporal distribution (where applicable) were extracted and reporting trends across publications were assessed.

RESULTS

South Africa has 12 main human skeletal repositories, six affiliated with universities and six with museums. There are over 12 300 human skeletal remains housed across these repositories, mainly of cadaveric, archaeological, forensic (medico-legal), and unknown origin. Universities are primarily stewards of large cadaveric collections (n = ± 6 200); however, a few manage archaeological (n = ± 1 300) and forensic repositories (n = ± 1 000). Museums exclusively curate repositories of archaeological origin and approximately ± 3 700 archaeological individuals can be found countrywide.

CONCLUSIONS

The ethical challenges faced by South African repositories are deeply connected to the country's colonial and apartheid history. Concerns related to consent, autonomy, cultural sensitivity, data availability and the respectful treatment of the deceased, require constant attention and consideration. We highlight several initiatives undertaken to address these issues, including the implementation of new management approaches by repositories, a shift away from using unclaimed bodies, efforts in deaccessioning and repatriation and an increased focus on community engagement.

Drying the mystery: a novel electronic sensor to quantify soft-tissue desiccation and natural mummification for forensic taphonomy

This study investigates the desiccation process of soft-tissue in South Africa, analyzing its interaction with environmental parameters and its implications for estimating the post-mortem interval. Through the examination of four decomposing porcine bodies across two summer seasons and one winter season, the research quantifies desiccation patterns using custom-designed and constructed printed circuit boards to measure the moisture content of body tissue over time. Generalized additive models were used to determine the environmental forces driving desiccation. Tissue resistivity was tested against the environmental predictor variables to determine the amount of variation they account for, and predicted values of the region-specific tissue resistivity variables were measured for each decomposing body. Results reveal distinct desiccation trajectories between summer and winter, with summer conditions conducive to precocious natural mummification. Environmental factors, particularly temperature and solar radiation, emerge as significant drivers of desiccation. This study represents the first quantitative analysis of deep tissue desiccation internationally, but also the first quantitative assessment of desiccation and natural precocious mummification in the Western Cape, South Africa. The exploration of desiccation as a potential indicator for estimating PMI opens new avenues for research and the integration of innovative methodologies and technologies promises to revolutionize forensic taphonomy practices.

Forensic taphonomic experimental design matters: a study assessing clothing and carrion biomass load on scavenging in Cape Town, South Africa

The identification of unknown human remains is a significant and ongoing challenge in South Africa, worsened by the country's high murder rate. The rate of decomposition in South Africa is significantly influenced by vertebrate scavenging, which, if not considered, can impede the accurate estimation of the post-mortem interval. Scavenging patterns vary greatly depending on the environment and ecological region, and there is limited data for the Western Cape province. To address this gap, two clothed and uncaged pig carcasses weighing 60 kg each were placed in the field in July 2021 and January 2022, respectively. Motion-activated infrared-capable trail cameras were used to observe decomposition, scavenger species, and their activities. Additionally, a comparative sample of 16 unclothed carcasses deployed between 2014 and 2016 in the same habitat were analyzed to assess the impact of clothing and biomass load. The study found three main results: (1) Regardless of habitat or biomass load, it took significantly less time to reach decomposition milestones (25%, 50%, and 75%) during the summer season; (2) the presence of mongoose scavengers had a greater impact on the time required to reach milestones during winter compared to summer; and (3) single carcass deployments reached the milestones faster than multi-carcass deployments in both seasons. This research highlights the potential inaccuracy of current methods for estimating the post-mortem interval when scavenging activity is not considered or documented in the underlying experimental data, particularly for environments or ecological biomes where scavengers actively impact decomposition rates.

The impact of climate change and sustainability initiatives on forensic practice

The climate change crisis affects all aspects of our lives, and this includes national and global scientific endeavours. The forensic sciences are no different but are yet to engage meaningfully with this agenda or to consider what it means for future practice. This paper explores and discusses a range of impacts on forensic and crime scene practice derived from climate change and proposes the potential implications. The paper concludes by laying out a way forward and a programme of activity to support the forensic sciences to manage the implications of climate change and related sustainability initiatives on the criminal and medico-legal investigative community.

Portion size matters: Carrion ecology lessons for medicolegal death investigations-A study in Cape Town, South Africa

Forensic taphonomic studies are regionally specific and improve time since death estimates for medico-legal casework. Within forensic taphonomy and carrion ecology, vertebrate scavengers are under-researched with many studies conducted using multiple, unclothed carcasses. This is a forensically unrealistic experimental design choice with unknown impact. The effect of variation in carrion biomass on the decomposition ecosystem, particularly where vertebrate scavengers are concerned, requires clarification. To assess the effect of carrion biomass load on vertebrate scavenging and decomposition rate, seasonal baseline data for single, clothed ~60 kg porcine carcasses were compared to clothed multiple-carcass deployments, in a forensically relevant habitat of Cape Town, South Africa. Decomposition was tracked via weight loss and bloat progression and scavenging activity via motion-activated cameras. The single carcasses decayed more quickly, particularly during the cooler, wetter winter, strongly correlated with concentrated Cape gray mongoose (Galerella pulverulenta) scavenging activity. On average and across seasons, the single carcasses lost 68% of their mass by day 32 (567 accumulated degree days [ADD]), compared to 80 days (1477 ADD) for multi-carcass deployments. The single carcasses experienced substantially more scavenging activity, with longer visits by single and multiple mongooses, totaling 53 h on average compared to 20 h for the multi-carcass deployments. These differences in scavenging activity and decay rate demonstrate the impact of carrion biomass load on decomposition for forensic taphonomy research. These findings need corroboration. However, forensic realism requires consideration in taphonomic study design. Longitudinally examining many single carcasses may produce more forensically accurate, locally appropriate, and usable results.

A synthesis of carcass decomposition studies conducted at a tropical (Aw) taphonomy facility: 2013-2022

Decomposition studies have been conducted in several regions of the world, but relatively few have investigated taphonomy in tropical environments. Even fewer have explored carcass decomposition during multiple tropical seasons, leaving the relationships between season and decomposition in tropical environments poorly understood. Ten decomposition studies using 30 carcasses were conducted in Honolulu, Hawaii, USA to start addressing this knowledge gap. These studies show that some postmortem processes were observed regardless of season. Carcass temperature and chemistry were spatiotemporally variable. Fly larval masses were consistently observed within 3 days (∼75 ADD) postmortem and carcasses lost 60%-90% of mass by 10 days (∼250 ADD) postmortem (Total Body Score ∼26). Season had a significant effect on decomposition, yet the warmest and most humid seasons did not always result in the most rapid and extensive decomposition. Seasonal variation appears to be less pronounced than at other tropical decomposition sites.