Inferring ancestral origin using a single multiplex assay of ancestry-informative marker SNPs

Tests that infer the ancestral origin of a DNA sample have considerable potential in the development of forensic tools that can help to guide crime investigation. We have developed a single-tube 34-plex SNP assay for the assignment of ancestral origin by choosing ancestry-informative markers (AIMs) exhibiting highly contrasting allele frequency distributions between the three major population-groups. To predict ancestral origin from the profiles obtained, a classification algorithm was developed based on maximum likelihood. Sampling of two populations each from African, European and East Asian groups provided training sets for the algorithm and this was tested using the CEPH Human Genome Diversity Panel. We detected negligible theoretical and practical error for assignments to one of the three groups analyzed with consistently high classification probabilities, even when using reduced subsets of SNPs. This study shows that by choosing SNPs exhibiting marked allele frequency differences between population-groups a practical forensic test for assigning the most likely ancestry can be achieved from a single multiplexed assay.     

Sensitive and specific quantification of human genomic deoxyribonucleic acid (DNA) in forensic science specimens: casework examples.

We describe the forensic science application of a method for quantification of human genomic deoxyribonucleic acid (DNA). The two cases cited in this report involve DNA samples extracted from skin tissue and bloodstained clothing recovered from different crime scenes. High-molecular-weight DNA was recovered from both specimens, and the concentrations of these DNAs were estimated to be approximately 0.5 microgram/microL by ethidium bromide/agarose gel electrophoresis. Using the human-specific DNA probe p17H8 (locus D17Z1) to quantify the amount of human genomic DNA in these samples, it is shown that less than 1% of the DNA isolated from the skin tissue is of human origin and that the DNA isolated from the bloodstained clothing is effectively devoid of human DNA sequences. These case examples illustrate the need to quantify not only the total amount of DNA recovered from forensic casework material, but also the proportion of the DNA that is of human origin.     

Clinically Significant Trauma Symptoms and Behavioral Problems in a Community-based Sample of Children Exposed to Domestic Violence

This study assessed the associations of characteristics of domestic violence incidents with clinically significant levels of traumatic symptoms and behavioral problems in a socio-economically and ethnically mixed sample of 687 children participating in a community-service program for children witnessing violence. Study predictors included child/family demographic characteristics, type and chronicity of exposure, and child’s perceptions of control over the event and threat to personal safety. Outcomes consisted of traumatic symptoms and behavior problems. Results showed that perceived threat and control were associated with greater odds of clinically significant levels of several trauma symptoms (and behavior problems in the case of perceived threat) after adjusting for effects of demographic factors and violence characteristics. Child co-victimization increased odds of reaching clinically significant levels of traumatic symptoms compared to children who witnessed the event but were not victimized. Female sex and White ethnicity increased odds of specific trauma symptoms and behavior problems. Increasing age reduced odds of some trauma symptoms. Associations between predictors and one outcome measure did not generalize across the other outcome measure. Implications of study findings, and directions for future research are discussed.     

Sexual asphyxia in siblings

We present an accidental autoerotic asphyxiation of a 24-year-old man. Further investigation revealed that 18 years earlier, his brother, then 13, had been found dead, hanging in the family bathroom. Although that death had been ruled a suicide, reevaluation of the death scene indicates that this was also an autoerotic asphyxiation. This is the first reported case of sexual asphyxia involving siblings.