用Y—染色体特异DNA探针鉴识微量干血痕性别的研究

法医鉴识干血痕性别,通常是用盐酸阿地平染色观察 Y—小体的方法。重组 DNA 技术的发展与应用,为法医物证检验开辟了新的领域。本文用 Y—染色体特异 DNA 探针鉴识干血痕性别的成功,为法医的血痕性别签定,提供了一种新的检验方法。     

浓缩DNA法结合miniSTR分型技术检验微量DNA

目的优化低拷贝数DNA STR分型方法。方法对采用磁珠法或Chelex-100法提取DNA,Identi-filer试剂盒扩增,未获得分型结果的日常检案检材,采用物理浓缩法或过柱浓缩法浓缩DNA,采用miniFilerTM试剂盒再次扩增分型。结果 127例检材中,47例磁珠法提取DNA未获得分型的样品,分型成功率为36%;80例Chelex-100法提取DNA未获分型的样品,分型成功率为30%。结论采用浓缩法和miniFilerTM试剂盒,可以提高日常检案中低拷贝数检材的STR检验分型成功率。     

Public and family support and concerns for providing DNA to law enforcement in long-term missing person cases

The identification of long-term missing persons and unidentified human remains is a global challenge. Many people stay on missing persons registers, with unidentified human remains stored for extended periods in mortuaries around the world. Research exploring public and/or family support for providing DNA in long-term missing persons cases is scarce. The aims of this study were to examine whether trust in police predicted the level of support for providing DNA and explore public/family support and concerns for providing DNA in such cases. Trust in police was measured through two widely used empirical attitude scales; “The Measures of Police Legitimacy and Procedural Justice”. Support and concerns for giving DNA were measured through four hypothetical missing persons case scenarios. The results showed more positive attitudes towards police legitimacy and procedural justice significantly predicted support, with the percentage level of positive support across the four case types as follows: cases involving a long-term missing child (89%), elderly adult with dementia (83%), young adult with a history of runaway (76%), with the lowest level of support for an adult with an estranged family (73%). Participants also reported more concerns about providing DNA when the missing person circumstances involved family estrangement. Understanding levels of public/family support and concerns around providing DNA to police in missing persons cases is vital to ensure that DNA collection practices reflect what the public/family support and, wherever possible, alleviate public concerns.     

Investigating the morphology and genetics of scalp and facial hair characteristics for phenotype prediction

Microscopic traits and ultrastructure of hair such as cross-sectional shape, pigmentation, curvature, and internal structure help determine the level of variations between and across human populations. Apart from cosmetics and anthropological applications, such as determining species, somatic origin (body area), and biogeographic ancestry, the evidential value of hair has increased with rapid progression in the area of forensic DNA phenotyping (FDP). Individuals differ in the features of their scalp hair (greying, shape, colour, balding, thickness, and density) and facial hair (eyebrow thickness, monobrow, and beard thickness) features. Scalp and facial hair characteristics are genetically controlled and lead to visible inter-individual variations within and among populations of various ethnic origins. Hence, these characteristics can be exploited and made more inclusive in FDP, thereby leading to more comprehensive, accurate, and robust prediction models for forensic purposes. The present article focuses on understanding the genetics of scalp and facial hair characteristics with the goal to develop a more inclusive approach to better understand hair biology by integrating hair microscopy with genetics for genotype-phenotype correlation research.     

Start-up of the criminal genetic database in Mendoza,Argentina

The usefulness of DNA databases is widely known and demonstrated. After the successful experiences of the UK and the USA the creation of databases increased rapidly around the world. In Latin America the implementation was slower and more problematic, with Chile and Uruguay being the first to implement them. In Argentina the problems were greater and more persistent.Although the lack of legislation or applicable laws is a generalized problem, the most difficult one to overcome was the lack of decision, interest and resources by those responsible at an institutional level.In 2016, Mendoza province modified its database law by creating the “Registro Provincial de Huellas Genéticas Digitalizadas” which allowed the process of construction and consolidation to begin. From January 2017 all prisoners, convicted and imputed of all types of crimes began to be sampled. This made the database to grow rapidly, reaching 13.821 samples in that year.During 2018, in addition to the daily imputed individuals, we began with the sampling from all the Mendoza Police Department, including the Scientific Police that deals with the crime scene. At present the database has a total of 40.652 individuals.In August 2018, the FBI's CODIS system was installed, and later the data loading process began. In 12 months we have reached 87 match or hits of which 46 correspond to sexual assault, 17 to robbery, 16 to homicides and the rest to other cases. Given that within the sexual abuse cases we were able to identify several serial sexual offenders, the 87 hits allowed clarifying 174 criminal cases.These results reaffirm the potential of the databases and gives a light of hope for victims of crime.In this work we present the advances and challenges that we faced in a chronological order.     

Assessing the performance of quantity and quality metrics using the QIAGEN Investigator® Quantiplex® pro RGQ kit

The Quantiplex® Pro RGQ kit quantifies DNA in a sample, supports the detection of mixtures and assesses the extent of DNA degradation based on relative ratios of amplified autosomal and male markers. Data show no significant difference in the accuracy and sensitivity of quantification between this and the Promega PowerQuant® System, both detecting the lowest amount of DNA tested, 4 pg. Laboratory controlled mixed male:female DNA samples together with mock sexual assault samples were quantified across a range of mixture ratios. Analysis software detected mixed DNA samples across all ratios for both quantification kits. Subsequent STR analysis using the Investigator® 24Plex QS Kit was able to corroborate mixture detection down to 1:25 male:female DNA ratios, past which point mixtures appeared identical to single-source female samples. Analysis software also detected laboratory degraded DNA samples, with data showing a positive trend between the Degradation Index (DI) and length of time of sonication. When used on ancient remains the assay was able to triage samples for further analysis, and STR profiles were concordant with DNA quantification results in all instances. STR analyses of laboratory-controlled sensitivity, mixture, and degradation studies supports the quality metric obtained from quantification. These data support the use of the Quantiplex® Pro RGQ kit for sample screening and quantification in forensic casework and ancient DNA studies.     

Towards molecular autopsies: Development of a FFPE tissue DNA extraction workflow

Sudden unexpected death (SUD) is a devastating event and forms a substantial proportion of the cases investigated at forensic mortuaries each year. Despite post-mortem investigations, the cause of death may remain undetermined. There is potential for these unresolved cases to benefit from retrospective molecular autopsies for investigation into genetic mutations which may have contributed towards death. Often, formalin fixed paraffin embedded tissues (FFPET) are the only archival sources of DNA available for retrospective analyses. However, extracting usable DNA from FFPET is challenging as current methods yield poor quality and quantity DNA. Thus, this study aimed to optimise DNA recovery from FFPET by investigating several variables within the DNA extraction workflow, including the selection of tissue type, number and thickness of tissue sections, deparaffinisation method, and DNA extraction kit. The quantity and quality of DNA recovered were assessed using spectrophotometry, real time PCR, digital capillary electrophoresis and DNA profiling. This study was the first to implement a nuclei quantification using microscopy to guide the selection of the best tissue type to use for DNA analysis. The use of a greater number of thinner tissue sections (100 sections, each 1 μm) significantly improved DNA concentration, purity and fragment length. Additionally, the combination of Deparaffinization Solution with the QIAamp® DNA FFPE Tissue Kit proved most favourable with a median DNA yield of 320 ng and 55% of DNA fragments greater than 400 bp. Isolated DNA was of single source, indicating no contamination in the workflow, and FFPET blocks that were stored for up to 3.5 years did not significantly affect DNA degradation (p = 0.1764). These results are especially informative for designing library preparation and sequencing workflows for determining cause of death in unresolved SUD cases.     

Mitochondrial DNA Extraction from Burial Soil Samples at Incremental Distances: A Preliminary Study

Preservation variance of soil DNA is neglected in the literature, and exceptional cases exaggerate amplification capabilities. This study sought to amplify a short mitochondrial fragment (212 bp) specific to Sus scrofa domesticus from the soil surrounding decomposing pig remains from an open‐air locale. Samples collected above the body at incremental distances after 145 days of initial placement yielded pig DNA. A secondary sampling was collected in 2017, approximately 768 days after burial. Inhibition tests corroborated that pig DNA was no longer present in the soil resulting in a loss of original DNA between 145 and 768 days. The results provide evidence that genetic material leaches out radially from the source and DNA fragments longer than 200 bp do not persist in soil for a relatively short timeframe in western Montana. The conclusions support the collection of soil in crime scene investigation procedures within the first few months of decomposition.     

Familial DNA searching- an emerging forensic investigative tool

In recent years, jurisdictions across the United States have expressed a growing interest in aiding criminal investigations through the use of familial DNA searching (FDS)- a forensic technique to identify family members through DNA databases. The National Survey of CODIS Laboratories surveyed U.S. CODIS laboratories about their perceptions, policies, and practices related to FDS. In total, 103 crime labs completed the survey (77% response rate). Labs in 11 states reported using FDS, while labs in 24 states reported using a similar-but distinct- practice of partial matching. Although the majority of labs had positive perceptions about the ability of FDS to assist investigations, labs also reported a number of concerns and challenges with implementing FDS. Respondents reported using either practice a limited amount with modest numbers of convictions resulting from both FDS and partial matching. The article reports on varying practices related to official policies, training, eligibility, the software search, lineage testing, requirements for releasing information, and subsequent investigative work. Finally, the article discusses what can be learned from this survey, accompanying limitations, and implications for decision-makers considering using FDS.