Jolandie Myburgh

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

The validity of the method in which total body score (TBS) and accumulated degree-days (ADD) are used to estimate the postmortem interval (PMI) is examined. TBS and ADD were recorded for 232 days in northern South Africa, which has temperatures between 17 and 28 °C in summer and 6 and 20 °C in winter. Winter temperatures rarely go below 0°C. Thirty pig carcasses, which weighed between 38 and 91 kg, were used. TBS was scored using the modified method of Megyesi et al. [1]. Temperature was acquired from an on site data logger and the weather station bureau; differences between these two sources were not statistically significant. Using loglinear random-effects maximum likelihood regression, an r(2) value for ADD (0.6227) was produced and linear regression formulae to estimate PMI from ADD with a 95% prediction interval were developed. The data of 16 additional pigs that were placed a year later were then used to validate the accuracy of this method. The actual PMI and ADD were compared to the estimated PMI and ADD produced by the developed formulae as well as the estimated PMIs within the 95% prediction interval. A validation of the study produced poor results as only one pig of 16 fell within the 95% interval when using the formulae, showing that ADD has limited use in the prediction of PMI in a South African setting.

Scoring of Decomposition: A Proposed Amendment to the Method When Using a Pig Model for Human Studies†

Decomposition studies often use pigs as proxies for human cadavers. However, differences in decomposition sequences/rates relative to humans have not been scientifically examined. Descriptions of five main decomposition stages (humans) were developed and refined by Galloway and later by Megyesi. However, whether these changes/processes are alike in pigs is unclear. Any differences can have significant effects when pig models are used for human PMI estimation. This study compared human decomposition models to the changes observed in pigs. Twenty pigs (50–90 kg) were decomposed over five months and decompositional features recorded. Total body scores (TBS) were calculated. Significant differences were observed during early decomposition between pigs and humans. An amended scoring system to be used in future studies was developed. Standards for PMI estimation derived from porcine models may not directly apply to humans and may need adjustment. Porcine models, however, remain valuable to study variables influencing decomposition.

An assessment of the repeatability of pubic and ischial measurements

Forensic anthropologists frequently use measurements of the human skeleton to determine sex and ancestry. Since the establishment of the Daubert criteria of admissibility of scientific evidence to court, methodologies used by anthropologists came under severe scrutiny. It is therefore important to ensure that the osteometric standards that are used in skeletal analyses are clearly explained, repeatable and reliable. Adams and Byrd (2002) found that measurements of the pelvis that originated from a point inside the acetabulum could not be repeated accurately. The purpose of this paper was to use three different sets of pubic and ischial measurements to establish whether they can be repeated with high precision between four different observers, and also by the observers themselves. Generally, high levels of repeatability were obtained, with intra-class correlations (ICC) above 0.8. Pubic and ischial measurements using a point in the acetabulum as origin performed the worst (ICC values of 0.82 and 0.79 respectively for inter-observer repeatability), whereas other methods performed better with ICC values above 0.9. It is advised that pubic and ischial measurements should be taken using the origin of the iliac blade as landmark.

Decomposition patterns of buried remains at different intervals in the Central Highveld region of South Africa

Burial of remains is an important factor when one attempts to establish the post-mortem interval as it reduces, and in extreme cases, excludes oviposition by Diptera species. This in turn leads to modification of the decomposition process. The aim of this study was to record decomposition patterns of buried remains using a pig model. The pattern of decomposition was evaluated at different intervals and recorded according to existing guidelines. In order to contribute to our knowledge on decomposition in different settings, a quantifiable approach was followed. Results indicated that early stages of decomposition occurred rapidly for buried remains within 7–33 days. Between 14 and 33 days, buried pigs displayed common features associated with the early to middle stages of decomposition, such as discoloration and bloating. From 33 to 90 days advanced decomposition manifested on the remains, and pigs then reached a stage of advanced decomposition where little change was observed in the next ±90–183 days after interment. Throughout this study, total body scores remained higher for surface remains. Overall, buried pigs followed a similar pattern of decomposition to those of surface remains, although at a much slower rate when compared with similar post-mortem intervals in surface remains. In this study, the decomposition patterns and rates of buried remains were mostly influenced by limited insect activity and adipocere formation which reduces the rate of decay in a conducive environment (i.e. burial in soil).

Age estimation from the acetabulum in South African black males.

Anthropologists are constantly seeking to improve methods for age estimation in the human skeleton. A new method was introduced about a decade ago that assesses the morphological changes that take place in the acetabulum as an individual ages. The pelvis is usually well preserved in forensic cases, which makes this method potentially valuable as an adult age indicator. This method employs seven variables, each with its own set of phases. To test the accuracy and reliability of this method, 100 black South African male acetabula from the Pretoria Bone Collection were assessed based on the criteria described in the original study. Box plots and transition curves were constructed to establish whether progression with age was visible and how it could possibly be modelled. Inter-observer reliability was also assessed by making use of Fleiss’s Kappa statistic. Five specimens were used as out-of-sample examples for which maximum likelihood (point) estimates were calculated. The results demonstrated that middle and older individuals’ age estimates were vastly underestimated. Inter-observer repeatability was poor, which suggested that the classification system most likely needs to be modified. A discussion and recommendation is given for improvement of reliability and repeatability of this method.

Secular trends in stature of late 20th century white South Africans and two European populations

During the 20th century a general positive secular trend for stature is observed in developed countries around the world while shorter statures, often associated with a lack of a positive secular trend, have mostly been observed in populations with lower SES. The purpose of this study was to compare secular changes in stature between 20th century South Africans of European descent and two European populations. The comparative samples include Dutch males with which there is an assumed genetic relationship, and Swiss males for which the genetic association is less clear. The sample comprised anthropometric stature data of white South Africans (17-62 years), Swiss and Dutch males (18-21 years) obtained from military conscripts with birth cohorts of 5 years from 1946 to 1995. The stature of white South African males did not increase at a significant rate compared to those observed in Swiss and Dutch males. South African and Dutch males were of similar height following World War II, but a considerable trend was observed only in the Dutch group. The Swiss group was initially shorter than the South Africans, but due to a positive secular trend their average stature is on a par with that of South Africans in the most recent cohort. The lack of a significant positive secular trend in the South African group could suggest that factors such as gene flow and poor economic and social development in South Africa resulted in shorter statures in white South African groups than expected.

A comparison between decomposition rates of buried and surface remains in a temperate region of South Africa

Several studies have been conducted on decomposition patterns and rates of surface remains; however, much less are known about this process for buried remains. Understanding the process of decomposition in buried remains is extremely important and aids in criminal investigations, especially when attempting to estimate the post mortem interval (PMI). The aim of this study was to compare the rates of decomposition between buried and surface remains. For this purpose, 25 pigs (Sus scrofa; 45–80 kg) were buried and excavated at different post mortem intervals (7, 14, 33, 92, and 183 days). The observed total body scores were then compared to those of surface remains decomposing at the same location. Stages of decomposition were scored according to separate categories for different anatomical regions based on standardised methods. Variation in the degree of decomposition was considerable especially with the buried 7-day interval pigs that displayed different degrees of discolouration in the lower abdomen and trunk. At 14 and 33 days, buried pigs displayed features commonly associated with the early stages of decomposition, but with less variation. A state of advanced decomposition was reached where little change was observed in the next ±90–183 days after interment. Although the patterns of decomposition for buried and surface remains were very similar, the rates differed considerably. Based on the observations made in this study, guidelines for the estimation of PMI are proposed. This pertains to buried remains found at a depth of approximately 0.75 m in the Central Highveld of South Africa.

Inter- and intraclass correlations for three standard foot radiographic measurements for plantar surface angles. Which measure is most reliable?

BACKGROUND The purpose of this study was to evaluate the reliability and reproducibility of three commonly used radiographic measures for plantar surface angles. METHODS The calcaneal angle (CA), calcaneal pitch angle (CPA), and length-height index (LHI) was measured by three independent examiners on two occasions on lateral foot radiographs. Intra- and inter-rater correlations were calculated using a general linear estimate model and post-hoc tests for repeated measures. Bland-Altmans plots with limits of agreement were used for observer differences in scores. RESULTS The intra-class correlations for the CA ranged from 0.91 to 0.94, for the CPA from 0.93 to 0.98, and for the LHI from 0.96 to 0.97. The inter-class correlations were 0.80 for CA, 0.83 for CPA and 0.93 for LHI. CONCLUSIONS The results of this study strongly suggest that the length-height index was the most consistent and reliable measure for arch height. LEVEL OF EVIDENCE Diagnostic Level II, validity.