A test of sex determination from measurements of chest radiographs

Sexually dimorphic distinctions within the human thoracic area may include morphological as well as metric differences in the sternum and 4th rib. This research assesses the validity of a set of previously published measurements from chest radiographs and their use in contemporary forensic situations. The chest plates from 130 adult individuals of a known sample undergoing medico-legal post-mortem examination were examined at autopsy. Thoracic radiographs were taken using a Faxitron cabinet X-ray machine at 40 kV using Kodak Diagnostic Film Ready Pack X-Omat TL. Measurements were taken to the nearest millimetre using a sliding calliper. Logistic regression analysis of measurements of the sternum and 4th rib was undertaken to determine sex. Using 4th rib width and sternal area, sex was predicted at an accuracy of 95.8% for males and 90.3% for females.     

Does sexual dimorphism in facial soft tissue depths justify sex distinction in craniofacial identification?

Separation of male and female soft tissue depths into discrete groups for craniofacial identification implies that males and females differ enough from each other, with respect to this application, for this distinction to be useful. In this study, previously published soft tissue depth data were analyzed for sex separation. It was found that the variation within each sex was large while the variation between the sexes was small. Often the value of two standard deviations of the measurement for either sex was larger than the difference displayed between the means of each sex. Furthermore, opposite sex overlap in regions defined to be close to the male or female mean were found to be large and the amount of variance explained by sex was small (less than 6% on average). These results indicate that while male and female means at single craniofacial landmarks may differ slightly, and even at statistically significant levels, individual male and female soft tissue depths are often the same or very similar. On average, soft tissue depths of the face do display some sexual dimorphism but it is not marked and of little practical meaning for craniofacial identification where a single individual must be independently considered. Thus, there is little use in separate reporting of data for males and females and data should be combined to increase sample sizes.     

Empirical analysis of the STR profiles resulting from conceptual mixtures

Samples containing DNA from two or more individuals can be difficult to interpret. Even ascertaining the number of contributors can be challenging and associated uncertainties can have dramatic effects on the interpretation of testing results. Using an FBI genotypes dataset, containing complete genotype information from the 13 Combined DNA Index System (CODIS) loci for 959 individuals, all possible mixtures of three individuals were exhaustively and empirically computed. Allele sharing between pairs of individuals in the original dataset, a randomized dataset and datasets of generated cousins and siblings was evaluated as were the number of loci that were necessary to reliably deduce the number of contributors present in simulated mixtures of four or less contributors. The relatively small number of alleles detectable at most CODIS loci and the fact that some alleles are likely to be shared between individuals within a population can make the maximum number of different alleles observed at any tested loci an unreliable indicator of the maximum number of contributors to a mixed DNA sample. This analysis does not use other data available from the electropherograms (such as peak height or peak area) to estimate the number of contributors to each mixture. As a result, the study represents a worst case analysis of mixture characterization. Within this dataset, approximately 3% of three-person mixtures would be mischaracterized as two-person mixtures and more than 70% of four-person mixtures would be mischaracterized as two- or three-person mixtures using only the maximum number of alleles observed at any tested locus.     

Evaluation of sieving polymers for fast, reproducible electrophoretic analysis of short tandem repeats (STR) in capillaries

Efficient capillary electrophoretic STR analysis requires rapid, reproducible and robust separation of DNA fragments with reasonable capillary longevity--this is currently accomplished using proprietary commercial polymeric sieving matrices specifically developed for this separation. These matrices, while effective, are costly and do not provide adequate resolution of STR DNA fragments in capillaries with shorter effective separation lengths, increasing the time required to accomplish the separation and minimizing the potential extrapolation to other miniaturized platforms. As the forensic community looks toward next generation microchip technology as a means of processing casework more rapidly, new sieving polymers need to be evaluated for utilization in this platform. The research presented here describes the assessment of commercially-available polymeric sieving matrices for STR analysis, with consideration given to feasibility of incorporation into a microdevice. Polymer composition, molecular weight, and concentration were evaluated, along with an assessment of the effects of buffer composition, separation temperature, and capillary length. These variables were evaluated individually or collectively on the ability to resolve STR DNA fragments and the reproducibility of the separations and the results compared to a proprietary commercial product. A 600,000 Da MW poly(ethylene oxide) (PEO) solution at a 3% (w/v) concentration was determined to be the most suitable matrix for these separations. This polymer, in coated capillaries, provided highly robust and reproducible separations, with near baseline resolution of fragments having single base differences. Reductions in the temperature of the separation, from 60 degrees C to 40 degrees C, and the urea concentration of the buffer, from 7 M to 3.5 M, provided increased longevity of the PEO polymer for repeated separations. Comparison of this polymer with currently specified commercial products used for STR analysis showed that the optimized PEO matrix provided superior separations under all conditions tested. In addition, PEO could be utilized in shorter capillary systems, with a concurrent decrease in analysis time, highlighting its potential for use in shortened capillary or microdevice systems.     

Acute selenium poisoning: suicide by ingestion

Selenium is a ubiquitous element in the environment essential to the human diet and widely utilized in industrial processes. Fatal human selenium intoxication is rare. The authors report a case in which investigators recovered a bottle of gun-bluing agent beside a 24-year-old man. He exhibited signs and symptoms typical of acute selenium intoxication presenting with nausea and vomiting, followed by pulmonary edema and rapid cardiovascular collapse approximately 3 to 4 h after ingestion. Classic electrocardiographic (EKG) changes, which have been reported to occur in acute selenium intoxication, included sinus tachycardia with ST wave alteration. Toxicological results confirmed elevated blood and tissue concentrations. The cause of death was ascribed to acute selenium intoxication, which ensued rapidly after oral consumption. The manner of death was suicide. This case report, which presents an overview of acute and chronic selenium poisoning, underscores the value of thorough toxicologic analyses of tissue and body fluids in humans.     

Detection of acetic acid in cadavers by gas chromatography

A simple technique of sample preparation for gas chromatographic test for acetic acid in cadaveric material has been developed. The background concentration of natural content of acetates in the stomach, liver and kidneys are determined. The error of the method is no more than 10% with standard deviation +/- 0.04-0.13.