Forensic Science International: Genetics Supplement Series最新文献

Frequency estimation for Y-STR haplotypes is a challenging problem because limited data are available and complex dependencies exist within the data. As a result, various statistical methods have been proposed for frequency estimation. The discrete Laplace method has been recommended in some contexts by the DNA commission of the ISFG. This method is limited to haplotypes with single integer repeat alleles only at all loci. We propose a generalisation of the method that handles duplicated loci such as DYS385 and less common alleles that are not integer repeats. The extension is implemented in an experimental R package called disclapmix2.

In this study, a DNA decision support tool was developed. With this tool we aim to gain insight in what actions are performed with which (types of) DNA profiles in casework, to improve decision making by DNA experts in future cases.

In the conventional method of DNA extraction from nails, it takes approximately half a day to dissolve the nails. In this study, we examined whether using the HOrizontal Nail MAshing (HONMA) method, in which pressure is applied to the nail to crush it flat and increase its surface area, would improve DNA extraction efficiency. Fingernails (5 mg) provided by ten volunteers were used as samples. Nail pieces (1–3 pieces), shredded with nail clippers, were thinly stretched by applying 2 t of pressure to each piece using a hydraulic press. DNA was extracted by incubation at 56 °C for 10 min and 1 h during proteolysis. DNA yield from the nails pretreated using the HONMA method increased by 0.20–7.10 times compared with that from unprocessed nails. In particular, 10-min incubation using the HONMA method resulted in an average 2.05-fold increase in DNA yield compared with that under overnight incubation. However, the impact of using the HONMA method varied widely among individuals, and the amount of extracted DNA decreased in some cases, suggesting that the yield may differ depending on the nail quality.

GeneMarker®HTS is a rapid, user-friendly software for forensic mtDNA and STR analysis with high throughput sequencing (HTS)/ next generation sequencing (NGS)/ massively parallel sequencing (MPS) data. Compared to the traditional capillary electrophoresis (CE) allele separation, HTS data provides a precise description of the repeat allele structure for each STR locus including the variants in the flanking areas for iso-allele genotype reporting and for future use in probabilistic genotyping analyses. The variants in the repeat region or the flanking area may in some cases cause failure for identification of STR/Y-STR alleles. To increase the accuracy, an iterated sequence alignment method is used to detect alleles. First, we align sequences to GRCh38 to determine the repeat sequence. Then, using the repeat sequence, we perform a second alignment that minimizes alignment errors and improves accuracy for repeat number. Stutters are also identified by stutter filters. To validate the method, concordance study is made and the concordance with the CE allele calls for 22 Autosomal STR Loci, 22 Chr Y STR Loci and Amelogenin is 100 % for NIST-2391d samples and 99.93 % for a 651 sample NIST-Promega dataset. The identification error due to sequence variants coupled with STR repeats is solved.

This work explores morphological and autofluorescence differences between vaginal and epidermal cells detectable through Imaging Flow Cytometry (IFC), a non-destructive, high-throughput technique. These differences were used to build a predictive framework for classifying unknown cells as originating from vaginal or epidermal tissue, which was tested on hand swabbings with and without digital penetration. Many more cells possessing a vaginal signature (median posterior probability ≥0.90) were detected in digital penetration samples than control hand swabbings. Minimum interpretation thresholds were developed to minimize/eliminate false positives; these thresholds were also effective when screening licked hands, indicating the potential utility of this method for a variety of biological mixture types and depositional events relevant to forensic casework.

SE33 was a well-known autosomal short tandem repeat (STR) marker that was high polymorphic and therefore was high discrimination power. The sequence structure of STR markers has been increasingly explored with next-generation sequencing (NGS) technology. The sequencing resulted in the development of a new locus designation and allele nomenclature that was also backward compatible with the conventional capillary electrophoresis. SE33 was one of the STR markers that had been coamplified by Forenseq™ Signature Prep Kit (Verogen) but were not analyzed and illustrated in the Universal Analysis Software (UAS) (Verogen). This study reported an ambiguous sequence-based allele 16.3 of the SE33 locus. This allele was observed while analyzed by STRait Razor 3.0. The configuration file was modified from the previous studies to include 15 bp of 5′ flanking region and 24 bp of 3′ flanking region. The ambiguous allele was called 16.3 (106 bp) with a read count of 2070. However, the sequence of the repeat region cannot be designated as allele 16.3. Several possible scenarios for allele designation were presented and discussed.

Cannabis sativa is a worldwide commercial plant used for medicinal purposes, food and fiber production, and also as a recreational drug. Therefore, the identification and differentiation between legal and illegal C. sativa is of great importance for forensic investigations. In this study, principal component analysis (PCA), an exploratory data analysis technique, was tested to correlate the specific genotype with the concentration of tetrahydrocannabinol (THC) in the samples. C. sativa samples were obtained from legal growers in Piedmont, Italy, and from illegal drug seizures in the Turin region. DNA was extracted, quantified, amplified with a 13-loci multiplex STR and finally analyzed with an automated sequencer. The results showed a trend in the analyzed samples as they differed by their THC content and allele profiles. PCA yielded two clusters of samples that differed by specific allele profiles and THC concentrations. Further validation studies are needed, but this study could provide a new approach to forensic investigation and be a valuable aid to law enforcement in significant marijuana seizures or in tracing illicit drug trafficking routes.

This study aimed to develop a methodology to identify biological fluids in sexual assault cases through mRNA markers. Biological fluid samples such as blood, saliva, and semen were collected from volunteers and submitted to RT-qPCR reactions with specific primers for the biomarkers HTN3 (saliva), ALAS (blood) andTGM4 (semen). The Melting (Tm) of each biological fluid was analyzed and the result inferred a high specificity capable of differentiating such traces. Biplex systems were generated to improve trace analysis in a single qPCR reaction.

DNA from door handles on entry doors could provide a clue as to who last left the scene. However, after years of extensive research on DNA transfer and persistence it can be considered common knowledge that general claims like "the last who touched leaves the most DNA" do not hold true. But who's DNA do we find on door handles that are usually used several times per day by the inhabitants? To assess this question, we sampled inside door handles from real-life burglaries and at the same time collected reference samples from all the inhabitants, to determine if we can detect any (major) profiles from non-inhabitants. We also searched to evaluate how often we detect DNA from the person who last touched the door handle as a (major) contributor. Only small amounts of DNA were recovered from the handles, originating most often, but not always, from inhabitants or even the last inhabitant touching the handle.

It is routine among many jurisdictions to recover DNA using tapelifts on porous substrates (e.g. clothing) and swabs on non-porous substrates (e.g. tool handles). Here, we examine this by comparing the efficiency of the NSW jurisdiction’s specific swabbing and tapelift techniques on a range of porous and non-porous substrates. To test DNA recovery efficiency, 30 μl aliquots of 1:50 and 1:100 saliva dilutions were deposited onto the substrates, left to dry overnight, recovered, extracted, quantified and a subset profiled. Tapelifts recovered more DNA and DNA profiles with more detectable alleles than swabs for both saliva dilutions on porous substrates. For non-porous substrates, similar DNA quantities and profiles were generally recovered with both methods for both saliva dilutions. These data underpin current practices to recover DNA using tapelifts for porous substrates and swabs for non-porous substrates. These data also revealed severe degradation of DNA recovered from brass, supporting the on-going need to improve DNA recovery and analysis methods for brass substrates.