Forensic DNA Typing From Femurs and Bones of the Foot: A Study of 3 Cases.

ABSTRACT: Evidence has been accumulating in the sense that femur may not always be the best option for DNA typing of skeletal remains. Recent studies have shown that bones of the hands and feet appear to be a superior source of preserved DNA. The current study reanalyzed DNA quantitation, degradation, and short tandem repeat typing in femurs, lateral cuneiforms, and distal foot phalanges. Data from 3 human identification cases involving corpses in an advanced decomposition state were collected. We found that in the studied cases, the femur provided equal or inferior results, recovering 84.9% of true alleles. Lateral cuneiforms (99.2%) and distal foot phalanges (96.8%) yielded higher percentages. In addition, more drop-ins and drop-outs were detected in femurs than cuneiforms and phalanges. This study adds to current findings that advocate for further investigation into bone selection for use in forensic practice. The impacts of our findings are limited by the small number of individuals studied and may not apply to old and degraded bones.

Human identification through DNA analysis of restored postmortem teeth.

The identification of human remains using DNA analysis can be extremely challenging and its success is certainly influenced by the time elapsed since death. In that context, intact teeth have been shown to be highly successful in DNA analysis. However, restored teeth are usually available and, surprisingly, these specimens have been poorly studied. In fact, there are no reports regarding forensic DNA analysis of those types of samples in real cases. Therefore, the aim of this study was to perform DNA typing on healthy and restored teeth from exhumed human remains, which had been buried for 46 years. A powder-free DNA extraction protocol specifically designed for teeth was followed and human DNA quantitation and degradation assessment was performed using an in-house qPCR assay. Samples were amplified with commercial human identification kits for autosomal and Y chromosome markers. The obtained DNA profiles were compared to those of a previously processed femur sample as well as a buccal swab from a putative son. One healthy and one restored tooth yielded complete, concordant and compatible DNA profiles with previously typed samples from the femur and the putative son. Biostatistical calculations supported the paternity relationship with a likelihood ratio greater than 11 million. The present study highlights the use of restored teeth in a real exhumation case and the powder-free approach specifically designed for the extraction of DNA from teeth is discussed.

DNA quantitation and degradation assessment: a quantitative PCR protocol designed for small forensic genetics laboratories.

For over 10 years, quantitative PCR (qPCR) for DNA quantitation has been reported in forensics. However, assays have not been described for small qPCR platforms. Thus, technological advancement is not always implemented in small forensic genetics laboratories. A duplex qPCR assay is reported, using a StepOne instrument and targeting a short and a long human DNA region. This study was performed according to international validation guidelines, including sensitivity, repeatability, reproducibility, precision, accuracy, contamination assessment, known and case-type samples, and degradation studies. Characterization of the genetic markers, species specificity, and population studies had already been conducted. Moreover, case-type samples were quantified, amplified using commercial kits and the number of alleles detected was recorded. Sensitivity was shown to be 10 pg/µL. Standard curve replicates demonstrated the assay is accurate, precise, as well as fairly repeatable and reproducible. The NGM Detect kit was shown to yield higher peaks than Identifiler Plus and NGM Select for degraded samples. Moreover, quality sensors were always present and proved useful. The quantification values of the large target showed a correlation with the number of alleles detected in the STR profiles for known and casework samples. The degradation index was shown to be informative, with a value of 10 or higher indicating dropout. It is suggested that after quantitation, samples with low or degraded DNA be amplified using newer amplification kits containing quality sensors to confirm that the low-quality profile was not affected by inhibition.

Male lineages in Brazilian populations and performance of haplogroup prediction tools.

The use of Y-chromosomal genetic markers in forensic investigations demands the establishment of reliable and representative DNA databases of different reference populations. The genetic characterization of the Y chromosome variation in human populations requires the analyses of haplotype frequencies allied to haplogroup determination. The present study aimed to contribute to the Brazilian database by providing 1,382 Yfiler Plus individual profiles, from 11 Brazilian states. The Yfiler Plus markers showed high haplotype diversities in all Brazilian populations (>0.9970), allowing high intra-population discrimination in forensic investigations. Pairwise genetic distances showed a homogeneity between Brazilian populations (FST ≤ 0.0043; non-differentiation p-values ≥ 0.0212), indicating that admixed populations from Brazil can be represented in a single Yfiler Plus haplotype database, for forensic purposes. The performance of Haplogroup Predictor and NevGen software in haplogroup prediction based on Yfiler Plus and Yfiler haplotypes was evaluated in a subset of 416 Brazilian samples that were also genotyped for 51 Y-SNPs. In 25% of the samples, no classification or errors were found for at least one of the prediction tools or marker sets. NevGen presented lower error rates (5.52% and 8.65% with Yfiler Plus and Yfiler, respectively) than Haplogroup Predictor (16.11% with Yfiler Plus and 13.70% with Yfiler). In conclusion, both haplogroup prediction tools can be useful to direct the SNP typing, but present large error rates to be used in forensic analysis, especially in predicting African haplogroups in admixed South American populations.

Living with the dead: A case report and review of the literature.

The discovery of human corpses in urban domestic settings does not constitute an unusual case in criminal casework. These scenarios can be very challenging to investigate since the uninformative evidences encountered also demand a multidisciplinary effort among several specialties in the forensic sciences field. The occurrence of this incident is usually accompanied by social isolation, which is an emblematic aspect of urban modern society. The elderly population is especially susceptible to being socially isolated, which is associated with higher mortality. We present a case report of an elderly woman who had been living with her husband's dead body, contributing to the scarce literature on the "Living with the Dead" phenomenon. The use of a multidisciplinary approach and the challenges that social isolation presents to forensic sciences and the contemporary society are discussed.