Ambika Flavel

Estimation of sex from sternal measurements in a Western Australian population

In Australia, particularly Western Australia, there is a relative paucity of contemporary population-specific morphometric standards for the estimation of sex from unknown skeletal remains. This is largely a historical artefact from lacking, or poorly documented, repositories of human skeletons available for study. However, medical scans, e.g. MSCT (multislice spiral computed tomography) are an ingenious and practical alternative source for contemporary data. To that end, this study is a comprehensive analysis of sternal sexual dimorphism in a sample of modern Western Australian (WA) individuals with a main purpose to develop a series of statistically robust standards for the estimation of sex. The sample comprises thoracic MSCT scans, with a mean of 0.9 millimeter (mm) slice thickness, on 187 non-pathological sterna. Following 3D volume rendering, 10 anatomical landmarks were acquired using OsiriX(®) (version 3.9) and a total of 8 inter landmark linear measurements were calculated using Morph Db (an in-house developed database application). Measurements were analyzed using basic descriptive statistics and discriminant function analyses, with statistical analyses performed using SPSS 19.0. All measurements are sexually dimorphic and sex differences explain 9.8-47.4% of sample variance. The combined length of the manubrium and body, sternal body length, manubrium width, and corpus sterni width at first sternebra contribute significantly to sex discrimination and yield the smallest sex-biases. Cross-validated classification accuracies, i.e., univariate, stepwise and direct function, are 72.2-84.5%, with a sex bias of less than 5%. We conclude that the sternum is a reliable element for sex estimation among Western Australians.

The application of traditional and geometric morphometric analyses for forensic quantification of sexual dimorphism: preliminary investigations in a Western Australian population

A current limitation of forensic practice in Western Australia is a lack of contemporary population-specific standards for biological profiling; this directly relates to the unavailability of documented human skeletal collections. With rapidly advancing technology, however, it is now possible to acquire accurate skeletal measurements from 3D scans contained in medical databases. The purpose of the present study, therefore, is to explore the accuracy of using cranial form to predict sex in adult Australians. Both traditional and geometric morphometric methods are applied to data derived from 3D landmarks acquired in CT-reconstructed crania. The sample comprises multi-detector computed tomography scans of 200 adult individuals; following 3D volume rendering, 46 anatomical landmarks are acquired using OsiriX (version 3.9). Centroid size and shape (first 20 PCs of the Procrustes coordinates) and the inter-landmark (ILD) distances between all possible pairs of landmarks are then calculated. Sex classification effectiveness of the 3D multivariate descriptors of size and shape and selected ILD measurements are assessed and compared; robustness of findings is explored using resampling statistics. Cranial shape and size and the ILD measurements are sexually dimorphic and explain 3.2 to 54.3 % of sample variance; sex classification accuracy is 83.5–88.0 %. Sex estimation using 3D shape appears to have some advantages compared to approaches using size measurements. We have, however, identified a simple and biologically meaningful single non-traditional linear measurement (glabella–zygion) that classifies Western Australian individuals according to sex with a high degree of expected accuracy (87.5–88 %).

Estimation of stature using anthropometry of feet and footprints in a Western Australian population

The aim of the study is to develop accurate stature estimation models for a contemporary Western Australian population from measurements of the feet and footprints. The sample comprises 200 adults (90 males, 110 females). A stature measurement, three linear measurements from each foot and bilateral footprints were collected from each subject. Seven linear measurements were then extracted from each print. Prior to data collection, a precision test was conducted to determine the repeatability of measurement acquisition. The primary data were then analysed using a range of parametric statistical tests. Results show that all foot and footprint measurements were significantly (P < 0.01-0.001) correlated with stature and estimation models were formulated with a prediction accuracy of ± 4.673 cm to ± 6.926 cm. Left foot length was the most accurate single variable in the simple linear regressions (males: ± 5.065 cm; females: ± 4.777 cm). This study provides viable alternatives for estimating stature in a Western Australian population that are equivalent to established standards developed from foot bones.

Brief communication: timing of spheno-occipital closure in modern Western Australians.

The spheno-occipital synchondrosis is a craniofacial growth centre between the occipital and sphenoid bones-its ossification persists into adolescence, which for the skeletal biologist, means it has potential application for estimating subadult age. Based on previous research the timing of spheno-occipital fusion is widely variable between and within populations, with reports of complete fusion in individuals as young as 11 years of age and nonfusion in adults. The aim of this study is, therefore, to examine this structure in a mixed sex sample of Western Australian individuals that developmentally span late childhood to adulthood. The objective is to develop statistically quantified age estimation standards based on scoring the degree of spheno-occipital fusion. The sample comprises multidetector computed tomography (MDCT) scans of 312 individuals (169 male; 143 female) between 5 and 25 years of age. Each MDCT scan is visualized in a standardized sagittal plane using three-dimensional oblique multiplanar reformatting. Fusion status is scored according to a four-stage system. Transition analysis is used to calculate age ranges for each defined stage and determine the mean age for transition between an unfused, fusing and fused status. The maximum likelihood estimates for the transition from open to fusing in the endocranial half is 14.44 years (male) and 11.42 years (female); transition from fusion in the ectocranial half to complete fusion is 16.16 years (male) and 13.62 years (female). This study affirms the potential value of assessing the degree of fusion in the spheno-occipital synchondrosis as an indicator of skeletal age.

Sex estimation using anthropometry of feet and footprints in a Western Australian population

An important component of forensic investigation is the identification of deceased (and increasingly living) individuals, which is often the role of the forensic anthropologist. One of the most valuable steps towards identification is via a biological profile, developed through the application of population specific standards. In disaster victim identification scenarios, fleshed feet are often recovered in footwear; footprints are another potential source of trace evidence found at crime scenes. In medico-legal investigations, feet and footprints can be useful for extrapolating living height, it is thus expedient to determine whether sex can be estimated from the same anthropometric data. The aim of the present study is to develop accurate sex estimation standards for a contemporary Western Australian population from measurements of the feet and footprints. The sample comprises 200 adults (90 males, 110 females). Three bilateral linear measurements were taken from each foot and seven bilateral measurements were acquired from static footprints obtained using a Podograph. A precision test was first conducted to assess data accuracy and reliability. Measurement data are then analysed using a range of parametric statistical tests. Results show that males were significantly (P<0.001) larger than females for all foot and footprint measurements; cross-validated sex classification accuracies ranged from 71% to 91%. Although in many instances the sex bias was large (>±5%), this study provides viable alternatives for estimating sex in Western Australian individuals with accuracy equivalent to established standards developed from foot bones.

Accuracy of a cut-off value based on the third molar index: Validation in an Australian population

According to Recommendation N°196 of the Australian Law Reform Commission (ALRC), the age at which a child reaches adulthood for the purposes of criminal law should be 18 years in all Australian jurisdictions. With specific reference to age at majority, the only tooth with development spanning adolescence (and thus the legally relevant 18 years of age) is the third molar, which limits the number of methods that can be applied from those available in the published literature. The aim of the present study is to test the accuracy of the third molar index (I3M=0.08), based on the correlation between chronological age and normalized measures of the open apices and height of the third mandibular molar, in order to assess the legal adult age of 18 years. Digital orthopantomographs of 143 living Australian subjects (72 boys and 71 girls) are analyzed. The results demonstrate that the sensitivity is 0.90 in boys and 0.90 in girls; associated specificity values are 0.85 and 0.87 respectively. We conclude that the cut-off value of I3M=0.08 is statistically robust and thus valid for forensic application in an Australian population.

Estimation of sex from the metric assessment of digital hand radiographs in a Western Australian population.

The forensic anthropologist is responsible for contributing to the identification of an unknown by constructing a biological profile from their skeletal remains. Towards achieving this goal, anthropologists can apply population and temporally specific standards with known error margins to morphometric data collected from a decedent. Recent research relating to the formulation of sex estimation standards has focussed on the assessment of bones other than the traditionally favoured pelvis and cranium, such as long bones of the appendicular skeleton. In particular, sex estimation standards based on morphometric data from metacarpals and phalanges have reported classification accuracy rates of 80% (and above) based on a narrow range of populations. The purpose of this study is to provide population-specific hand bone sex-estimation standards for a contemporary Western Australian population. The present study examines digital right hand radiographs of 300 adults of known age, equally represented by sex. A total of 40 measurements were taken in each hand (metacarpals and proximal phalanges); the measurements were then analysed using univariate statistics and cross-validated direct and stepwise discriminant function analysis. All hand bone measurements were significantly sexually dimorphic, with a tendency for the width measurements to express a higher degree of dimorphism than the length measurements. A maximum cross-validated classification accuracy of 91% was achieved with a sex bias of -6%. The standards presented here can be used in future forensic investigations that require sex estimation of hand bones in a Western Australian population.

Forensic age estimation in living individuals: methodological considerations in the context of medico-legal practice

The reconciliation of skeletal and chronological age is of paramount concern in the context of criminal proceedings involving living individuals, who frequently lack any associated identification documentation, and are referred to the criminal justice system. It is important to appreciate that skeletal and chronological ages are not the same measurement of time-since-birth, and depending on the analytical approaches applied, there will be an inher- ent source of variation between estimated (biological: skeletal, physical, and psychological) and actual (legal) age. Given the evidentiary value attached to the estimation of age based on the subjective assessment of biological and psychological developmental attributes, it is timely to consider current approaches toward achieving the latter. The aim of this review is to first explore a selection of circumstances that result in requests for forensic age assessment in living individuals. Issues pertaining to competency to perform an assessment, sources of error that may be introduced, and how to accordingly quantify the level of uncertainty in the final estimation are then considered. This logically leads into discussions of the necessity for population-specific statistical biological data. Current methods based on psychological development, dental status, and skeletal maturation are then reviewed. The review concludes by exploring future research and practical directions in the context of medico-legal practice

Skeletal age estimation in a contemporary Western Australian population using the Tanner–Whitehouse method

Various age estimation techniques have been utilised in Australia to evaluate the age of individuals who do not have documentation to determine legal majority/culpability. These age estimation techniques rely on the assessment of skeletal development as visualised in radiographs, CT scans, MRI or ultrasound modalities, and subsequent comparison to reference standards. These standards are not always population specific and are thus known to be less accurate when applied outside of the original reference sample, leading to potential ethical implications. Therefore, the present study aims to: (i) explore the variation in developmental trajectories between the established Tanner-Whitehouse (TW) age estimation standards and a Western Australian population; and (ii) develop specific hand-wrist age estimation standards for the latter population. The present study examines digital anterior-posterior hand-wrist radiographs of 360 individuals 0 to 24.9 years of age, equally represented by sex. Each radiograph was assessed using the RUS, Carpal and 20-bone methods of Tanner et al. The standard error of the estimate (SEE) was calculated for each method (range: ♀ SEE ±0.4-11.5 years; ♂ SEE ±0.9-10.1 years). The most accurate method was TW3 RUS for females and the TW2 Carpal system for males. The 50th centile skeletal maturity scores for each year age group were plotted against average chronological age to produce polynomial regression standards with a demonstrated accuracy of (♀ SEE ±0.09-3.46 years; ♂ SEE ±0.02-3.42 years) for females and males, respectively. The standards presented here can be used in future forensic investigations that require age estimation of hand-wrist bones in a Western Australian population, however, they are not appropriate for establishing age of majority (18 years), as skeletal maturity was attained on average earlier than 15 years of age in both sexes for all three systems examined.

Quantification of the timing of anterior fontanelle closure in a Western Australian population

Closure of the anterior fontanelle is generally accepted to occur within the first two years of life. However, statistical quantification of the precise timing of closure in a Western Australian population has not been explored. The current study examined MDCT scans of 68 individuals between birth and 3.91 years to assess the timing of anterior fontanelle closure. Using OsiriX, the scans are viewed in axial and multi-planar reconstructed (MPR) images and three-dimensional volume rendered reconstructions. Anterior fontanelle fusion status was quantified using two methods: calculating anterior fontanelle area and by taking the oblique linear distances of the open fontanelle. The single greatest proportion of fusion was shown to occur in the first year of life, by which stage only 47.19% of the fontanelle remains unfused (on average by area). There was only one individual demonstrating complete fusion before 1 year of age (0.86 years) with no single individual presenting an open fontanelle beyond 2.4 years of age. The current study outlines statistically quantitated data that facilitates forensic age estimation (either macroscopic or radiographic) specific to Australian individuals from the perinate to early childhood life stages.