Second GHEP-ISFG exercise for DVI: "DNA-led" victims' identification in a simulated air crash

Assessment of ForenSeq mtDNA Whole Genome Kit for forensic application

Mitochondrial DNA (mtDNA) is an indispensable genetic marker in forensic genetics. The emergence and development of massively parallel sequencing (MPS) makes it possible to obtain complete mitochondrial genome sequences more quickly and accurately. The study evaluated the advantages and limitations of the ForenSeq mtDNA Whole Genome Kit in the practical application of forensic genetics by detecting human genomic DNA standards and thirty-three case samples. We used control DNA with different amount to determine sensitivity of the assay. Even when the input DNA is as low as 2.5 pg, most of the mitochondrial genome sequences could still be covered. For the detection of buccal swabs and aged case samples (bloodstains, bones, teeth), most samples could achieve complete coverage of mitochondrial genome. However, when ancient samples and hair samples without hair follicles were sequenced by the kit, it failed to obtain sequence information. In general, the ForenSeq mtDNA Whole Genome Kit has certain applicability to forensic low template and degradation samples, and these results provide the data basis for subsequent forensic applications of the assay. The overall detection process and subsequent analysis are easy to standardize, and it has certain application potential in forensic cases.

Commercial Aircraft-Assisted Suicide Accident Investigations Re-Visited—Agreeing to Disagree?

Background: The number of aircraft-assisted suicides can only be considered a rough estimate because it is difficult and, at times, impossible to identify all cases of suicide. Methods: Four recent reports of accidents occurring in 1997 in Indonesia, 1999 in Massachusetts in the United States, 2013 in Namibia, and 2015 in France related to commercial aircraft-assisted suicides were analyzed. This analysis relied on data extracted from the accident reports that supported aircraft-assisted suicide from the: (a) cockpit voice recorder (CVR) and flight data recorder (FDR), (b) medical history, (c) psychosocial history, (d) toxicology, (e) autopsy, and (f) any methodology that utilized aviation medicine. There are some limitations in this study. Although all analyzed accident investigations followed ICAO Annex 13 guidelines, there is variability in their accident investigations and reporting. In addition, accident investigation reports represent accidents from 1997 to 2015, and during this time, there has been a change in the way accidents are reported. The nature of this analysis is explorative. The aim was to identify how the various aircraft accident investigators concluded that the accidents were due to suicidal acts. Results: In all four accident reports, FDR data were available. CVR data were also available, except for one accident where CVR data were only partially available. Comprehensive medical and psychosocial histories were available in only one of four of the accident reports. Conclusion: To prevent accidents involving commercial aircraft, it is necessary to identify the causes of these accidents to be able to provide meaningful safety recommendations. A detailed psychological autopsy of pilots can and likely will assist in investigations, as well as generate recommendations that will substantially contribute to mitigating accidents due to pilot suicide. Airborne image recording may be a useful tool to provide additional information about events leading up to a crash and thus assist in accident investigations.

Effects of DNA degradation and genotype imputation on high-density SNP microarray in pairwise kinship analysis

High-density single nucleotide polymorphisms (SNPs) can detect distant relatives even in the context of pairwise kinship analysis. Although DNA microarrays conveniently generate genome-wide SNP data, they require large quantities of high-quality DNA. Genotyping data obtained from low-quantity and low-quality samples are likely unreliable owing to the incidence of no-called or mistyped SNPs. In this study, we examined the effects of insufficient sample densities and sample degradation on the efficacy of kinship analysis. While low DNA amounts had a minor effect, DNA degradation led to a significant increase in no-call rates and error rates. Posterior probabilities of kinship determination, calculated using the index of chromosomal sharing, were markedly lower in proportion to the no-call rates and error rates. We also investigated the effect of genotype imputation to complement the no-called genome data utilizing SNPs reference panels. We found that the posterior probability of the relative-assumed person increased with genotype complementation in case of mild degradation, even with mistyped genotypes. Therefore, DNA microarray with imputation is a promising method for analyzing forensic DNA samples taken from situations where DNA quantity and quality may be compromised, such as disaster victim identification using pairwise kinship analysis.

Developmental Validation of the Novel Five-Dye-Labeled Multiplex Autosomal STR Panel and Its Forensic Efficiency Evaluation

Short tandem repeats (STRs) are the most frequently used genetic markers in forensic genetics due to their high genetic diversities and abundant distributions in the human genome. Currently, the combined DNA index system is commonly incorporated into various commercial kits for forensic research. Some novel STRs that are different from the combined DNA index system were not only used to assess complex paternity cases but also could provide more genetic information and higher forensic efficiency in combination with those commonly used STRs. In this study, we validated forensic performance of a novel multiplex amplification STR panel to evaluate its sensitivity, species specificity, forensic application values, and so on. Obtained results revealed that the kit showed high sensitivity, and the complete allelic profile could be observed at 0.125 ng DNA sample. In addition, the kit possessed high species specificity, good tolerance to common inhibitors, and accurate genotyping ability. More importantly, STRs out of the kit displayed high discrimination power and probability of exclusion. To sum up, the novel kit presented in this study can be viewed as a promising tool for forensic human identification and complex paternity analysis.

Precision DNA Mixture Interpretation with Single-Cell Profiling

Wet-lab based studies have exploited emerging single-cell technologies to address the challenges of interpreting forensic mixture evidence. However, little effort has been dedicated to developing a systematic approach to interpreting the single-cell profiles derived from the mixtures. This study is the first attempt to develop a comprehensive interpretation workflow in which single-cell profiles from mixtures are interpreted individually and holistically. In this approach, the genotypes from each cell are assessed, the number of contributors (NOC) of the single-cell profiles is estimated, followed by developing a consensus profile of each contributor, and finally the consensus profile(s) can be used for a DNA database search or comparing with known profiles to determine their potential sources. The potential of this single-cell interpretation workflow was assessed by simulation with various mixture scenarios and empirical allele drop-out and drop-in rates, the accuracies of estimating the NOC, the accuracies of recovering the true alleles by consensus, and the capabilities of deconvolving mixtures with related contributors. The results support that the single-cell based mixture interpretation can provide a precision that cannot beachieved with current standard CE-STR analyses. A new paradigm for mixture interpretation is available to enhance the interpretation of forensic genetic casework.