Maryna Steyn

Purpose: In 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.

Morphological analysis in forensic facial comparison was recently validated for judicial use. However, no image quality assurance systems exist for this purpose, despite image triage being considered the best practice approach. Hence, this study aimed at testing a semi-quantitative scoring method to assess image quality and investigated facial image resolution and lighting quality quantitatively in a context of forensic facial comparison. For this purpose, 400 facial comparison photographic and CCTV image pools developed from the Wits Face Database were used. These facial images were analysed in prior studies that investigated the validity of morphological analysis. A semi-quantitative image quality scoring system was adapted and tested on the above sample and compared across correct and incorrect matches obtained as part of previous studies using a logistic regression model. In addition, facial images were cropped to the closest pixel comprising the face, head and neck areas; then, a face-to-image pixel proportion was calculated as an estimator of resolution quality; and pixel exposure qualities were obtained to be compared to facial comparison outcomes. Ideal and high image quality scores were related to correctness of matches, while low-quality scores were related to incorrect matches. High pixel proportions were related to true matches and low exposure was related to false positives, while high exposure was related to false negatives. These results suggest that an easy method for image triage could be employed by scoring image quality. Quantitative measures should be investigated further for thresholding quality suitability for confidence of facial comparisons.

The study of human remains can provide valuable information about aspects of past populations. Here we present an updated database consisting of 590 radiocarbon (¹⁴C) dates for human remains from Holocene South Africa before European contact. We calibrated or recalibrated all the previously published dates using the most recent calibration curve for the southern hemisphere. Each date is roughly georeferenced and plotted according to their Stone Age or Iron Age contexts, revealing the broad distribution pattern of dated Holocene human remains across South Africa—perhaps reflecting aspects of past population distribution and densities, but also underscoring historical collection practices, archaeological research focus, and preservation conditions. We use Kernel Density Estimation models to show peaks and troughs of dated remains through time, with Later Stone Age peaks at ∼5.5 ka cal BP, ∼2 ka cal BP and ∼0.5 ka cal BP, and Iron Age peaks ∼1.1 ka cal BP and ∼0.5 ka cal BP, some of which show broad correspondence to climatic data. Our data, based on dated remains only, do not provide a full reflection of past populations, and our large-scale, coarse-grained analysis cannot yet assess the reasons for the peaks in dated human remains in detail. Yet, the study provides a new resource, and a data-driven overview that highlights aspects to be explored with further contextual analyses against the available archaeological records, population histories and climatic indicators through time and across space.

Age estimation in living individuals around the age of 18 years is medico-legally important in undocumented migrant cases and in countries like South Africa where many individuals are devoid of identification documents. Establishing whether an individual is younger than 18 years largely influences the legal procedure that should be followed in dealing with an undocumented individual. The aim of this study was to combine dental third molar and anterior inferior apophysis ossification data for purposes of age estimation, by applying a decision tree analysis. A sample comprising of 871 black South African individuals (n = 446 males, 425 = females) with ages ranging between 15 and 24 years was analyzed using panoramic and cephalometric radiographs. Variables related to the left upper and lower third molars and cervical vertebral ring apophysis ossification of C2, C3, and C4 vertebrae analyzed in previous studies were combined in a multifactorial approach. The data were analyzed using a pruned decision tree function for classification. Male and female groups were handled separately as a statistically significant difference was found between the sexes in the original studies. A test sample of 30 individuals was used to determine if this approach could be used with confidence in estimating age of living individuals. The outcomes obtained from the test sample indicated a close correlation between the actual ages (in years and months) and the predicted ages (in years only), demonstrating an average age difference of 0.47 years between the corresponding values. This method showed that the application of decision tree analysis using the combination of third molar and cervical vertebral development is usable and potentially valuable in this application.

Worldwide and in South African Stone Age contexts, much research has been done on the relationship between stature of past populations and general well-being, as well as trends and patterns in stature through time. This research is aimed at collating and assessing all available stature and long bone data for Bantu-speaker individuals living in the South African Iron Age. Data for only 25 female and 32 male individuals, dating from circa AD 550 to AD 1823, could be found. In general, methods used to reconstruct stature were inconsistent and data were poorly reported. From the available data, no clear trends or patterns in stature through time could be observed and stature seems to be on a par relative to those of early twentieth century individuals. Recommendations are made as to which methods to use in stature estimations in this context. The data provided in this research can serve as reference material for future similar studies and can assist in interpreting individual stature estimations from bioarcheological research in the region.

Worldwide and in South African Stone Age contexts, much research has been done on the relationship between stature of past populations and general well-being, as well as trends and patterns in stature through time. This research aimed at collating and assessing all available stature and long bone data for Bantu-speaker individuals living in the South African Iron Age. Data for only 25 female and 32 male individuals, dating from circa AD 550 to AD 1823, could be found. In general, methods used to reconstruct stature were inconsistent and data were poorly reported. From the available data, no clear trends or patterns in stature through time could be observed and stature seems to be on a par relative to those of early 20th century individuals. Recommendations are made as to which methods to use in stature estimations in this context. The data provided in this research can serve as reference material for future similar studies and can assist in interpreting individual stature estimations from bioarchaeological research in the region.

An age-at-death estimation method using the first rib may be particularly advantageous as this rib is relatively easy to identify, not easily damaged postmortem, and associated with less mechanical stresses compared to other age indicators. Previously, mixed results have been achieved using the first rib to estimate age-at-death. This study aimed to develop and test an age-at-death estimation method using the first rib. An identified modern black South African sample of 260 skeletons were used to collect age-related data from the first rib. Multiple linear regression analysis equations were created from this data for male, female, and combined samples. When tested on a hold-out sample, equations generated mean inaccuracies of 7–13 years for point estimates. The 95% confidence intervals contained the true age in 11–33% of individuals depending on the equation used, but wider intervals generated using 95% prediction intervals contained true ages for 100% of individuals. Point estimate inaccuracies are comparable to other age-at-death estimation methods and may be useful if single indicator estimation is unavoidable in the case of missing or damaged bones. However, combined methods that use indicators from many areas of the skeleton are preferable and may reduce interval widths.