Forensic Science International: Genetics Supplement Series最新文献

The high complexity of the genetic analysis of crime scene samples is mainly related to the unknown number of contributors, low DNA quantity and quality, and associated stochastic effects. The difficulty and subjectivity of interpreting casework samples was the motto for the development of software to mitigate these conditions and allow the quantification of the genetic evidence. Currently, there are several tools for statistical analysis of mixture samples based on either qualitative or quantitative models. The first considers the electropherograms’ qualitative information, while the latter also considers the associated quantitative information. This work’s main goal was to evaluate the effect that parameters’ settings variation may have on the LR computation, specifically the drop-in frequency parameter. For that, a qualitative – LRmix Studio – and two quantitative software – STRmix™ and EuroForMix – were considered and an intra-software analysis was performed, using as input real casework samples. The drop-in frequency variation showed an impact, leading to differences higher than four units (log₁₀ scale) for some pairs of samples. In addition, for some cases, no comparisons were performed either because the tool computed a null LR value or displayed an error message. Thus, this work reinforces the importance of proper parameters’ modeling and estimation in forensic casework evaluation.

With the increase in sensitivity of DNA profiling, questions about how and when the DNA was deposited have become a driving issue in forensic cases. To address this, we propose a novel method to determine time since deposition of trace DNA samples based on morphological and autofluorescence properties of individual epithelial cells which can change as the sample ages. To develop this signature, a series of trace DNA samples were generated by contact/handling a substrate and then allowed to age anywhere between one day and more than one year prior to collection. Imaging flow cytometry (IFC) was then used to characterize the morphology and autofluorescence profiles of individual cells within each sample followed by multivariate modelling and predictive classification.

Results

showed that epithelial cell populations could be classified with high accuracy (∼90%) into one of three time-since-deposition groups: < 1 week, between 1 week and 2 months, and > 2months. Differences across age groups were largely driven by decreases in brightfield contrast and increases in the intensity of autofluorescence. To further test this approach for forensic casework, 47 individual donor cell populations spanning each time deposition group were classified blindly against the remaining data set. Samples containing at least 75 cells and a posterior probability greater than 0.90 showed classification accuracies ∼95%. Accuracies for individual time groups were 97% (<1 week), 92% (1week-2months), 98% (>2 months) with an average posterior probability for all time groups ∼0.96. This indicates that autofluorescence and morphological analyses may provide probative information regarding time since deposition for many types of trace DNA samples in forensic casework.

An STR null allele is an allele at a microsatellite locus that fails to amplify. A possible cause is poor primer annealing due to nucleotide sequence divergence in the flanking primers. In this study, a woman (ZAM) wanted to know whether a man (PGAF) was the father of her child (ZGC). During the court settlement, PGAF died. PGAF’s parents refused to undergo DNA investigation and denied the access to biological fragments from their dead son. Although, DNA specimens were obtained from buccal swabs of ZAM, ZGC and PGAF’s paternal sister (PTFS). Initially, only autosomal profiles were studied, and kinship assignment was inconclusive. Following our requests, PGAF’s parents (PRGF and LLGM) led us to obtain their DNA specimens. Only with the PTFS genetic profile, we were not able to demonstrate a kinship assignment. PTFS showed a homozygosis at D8S1179 locus. Then, merely comparing PTFS, LLGM and ZGC autosomal genetic profiles it was possible to underline that they were three different homozygous at D8S1179 locus. Hence, comparing the peak heights in different loci and according to literature, they had to carry a null allele at this locus. Parental studies were completed by Y haplotype analysis.

In this study, Japanese and Han Chinese individuals (n = 32, each) were genotyped for 261 autosomal STRs, and allele frequencies were calculated for each locus in each population. The average number of alleles for all loci in Japanese and Han Chinese populations was 6.65 and 6.56, respectively. The tests for deviations from HWE performed using an exact test showed that the number of STRs (P > 0.05) in Japanese and Han Chinese populations was 236 and 241, respectively. Calculation of forensic parameters showed heterozygosity, and the exclusion means in the Japanese population were 0.7185 and 4813 and those in the Han Chinese population were 0.7308 and 0.5008. In addition, population genetic analyses, such as principal component analysis and factorial correspondence analysis, were performed and a differential formula with likelihood ratios was applied for various number of STR loci based on the effectiveness of differentiation between the two populations. Accordingly, this study suggests that statistical differentiation between genetically close populations, such as the Japanese and Han Chinese populations, is possible if approximately 40–50 effective STR loci are analyzed.

Currently, there are approximately 750 unidentified human remains and 2500 long-term missing persons in Australia. The Australian Federal Police National DNA Program for Unidentified and Missing Persons (Program) is using a multifaceted, multijurisdictional, multiagency, and multidisciplinary approach in a dedicated effort to identify these unknown deceased persons, scientifically link them to known missing persons, and provide answers to their families. The nationally coordinated Program provides its police, forensic, and coronial stakeholders with a suite of contemporary forensic technologies, databases, and experts to forensically examine the skeletonised remains and recover post-mortem data for comparison to the available ante-mortem data for each missing person. Through a number of physical and virtual public outreach activities, families with missing relatives have been encouraged to provide vital ante-mortem forensic information, records, and samples to aid the identification process. To date, this unique Program has assisted to resolve a number of unidentified and missing persons cases from both historical and contemporary contexts, using a combination of genetic and non-genetic techniques, and local and national databases. The centralisation of Program capabilities, expertise, and resources to conduct this type of unique and challenging casework is proving to be the most effective and efficient way to generate investigative leads, identify human remains, and resolve long-term missing persons cases in Australia.

We present a statistical method for biallelic SNP genotyping that reduces the risk of wrong SNP calls and gives fewer no-calls. The method uses a symmetric multinomial logistic regression model with an intuitive graphical interpretation. Its probabilistic nature gives the user control over the accepted risk through the estimated genotype probabilities. We compared the performance of our method with the HID SNP Genotyper v.4.3.1 plug-in (HSG) (Thermo Fisher Scientific) and the additional criteria of the University of Copenhagen (UCPH) through a series of six DNA dilutions from 500 pg to 16 pg DNA. The HSG method made wrong calls from 62.5 pg DNA and below, while the UCPH method made wrong calls at 16 pg DNA. Our method allowed SNP genotyping of 16 pg DNA without making wrong calls. Depending on the DNA dilution, our method also reduced the number of no-calls by 70–96 % compared to UCPH method and 59–69 % compared to the HSG method. Our method can be used for any biallelic genotyping.

In 2019, based on the publication of Law No. 13,812/2019, the National Policy on the Search for Missing Persons was created in Brazil. In this context, on March 2, 2020 the Steering Committee of the Integrated Network of DNA Databases (RIBPG) created the Working Group on Genetic Identification of Missing Persons. In 2021, the first National Campaign for the Collection of DNA from Relatives of Missing Persons was launched. This action provided the collection of relatives of more than 1700 missing people throughout Brazil. Since the beginning of the work, the number of genetic profiles related to the search for missing persons has increased by 216 % in the National DNA Database. So far, RIBPG has already managed to solve 223 disappearances throughout Brazil.

This study assessed the performance of five different DNA extraction methods for the recovery of DNA from bone: ChargeSwitch® gDNA Plant Kit, DNA IQ™ System Kit, DNeasy® Blood & Tissue Kit, PrepFiler® BTA Forensic DNA Extraction Kit and phenol-chloroform-isoamyl alcohol. DNA was extracted from pig rib and femur bones that was fresh, had undergone surface decomposition for three months, and had undergone surface decomposition for one year. Extracted DNA was analyzed using real-time PCR and amplification of an in-house PCR multiplex that assessed the quality and quantity of DNA and for the presence of inhibitors. The phenol-chloroform-based method consistently yielded the highest amounts of DNA and DNA IQ the lowest; however, all methods produced relatively high yields of DNA from both pig rib and femur samples that could be amplified without any detected inhibition. The data demonstrate that with reasonable quality bone samples any of the tested methods can isolate DNA that can be successfully analyzed. The effective use of internal PCR controls is also demonstrated.

For establishing databases that capture the existing diversity in populations, the sample collection strategy is a determining factor and caution must be taken when choosing the suitable approach. Many researchers choose to restrict the sampling to individuals with inheritance for three generations in a specific geographic location. However, the appropriate database in a forensic context is the one representing the current population. We analyzed mtDNA composition across generations in populations from Colombia, Ecuador, and Paraguay. An overall genetic homogeneity was detected, with statistically significant differences on macrohaplogroup frequencies for few department/regions.

At the Netherlands Forensic Institute, mRNA profiling for the purpose of organ tissue identification is frequently requested in casework. The previous version of the assay (denoted Organtyper) lacked markers for identifying adipose tissue, while this was occasionally questioned in casework. Here, three potential adipose markers are examined before incorporating one into the final Organtyper assay. The added value of the adipose marker becomes clear from looking at casework results.