The Usefulness of qPCR Data for Sample Pre-Assessment and Interpretation of Genetic Typing Results.

DNA quantification is a crucial step in the STR typing workflow for human identification purposes. Given the reaction's nature, qPCR assays may be subjected to the same stochastic effects of traditional PCR for low-input concentrations. The study aims to evaluate the precision of the PowerQuant® (Promega) kit assay measurements and the degree of variability for DNA templates falling below the optimal threshold of the PowerPlex® ESX-17 Fast STR typing kit (Promega). Five three-fold dilutions of the 2800 M control DNA (Promega) were set up. Each dilution (concentrations: 0.05, 0.0167, 0.0055, 0.00185, and 0.000617 ng/µL) was quantified and amplified in four replicates. Variability for qPCR results, STR profile completeness, and EPGs' peak height were evaluated. The qPCR-estimated concentration of casework samples was correlated with profile completeness and peak intensity, to assess the predictive value of qPCR results for the successful STR typing of scarce samples. qPCR was subjected to stochastic effects, of which the degree was inversely proportional to the initial input template. Quantitation results and the STR profile's characteristics were strongly correlated. Due to the intrinsic nature of real casework samples, a qPCR-derived DNA concentration threshold for correctly identifying probative STR profiles may be difficult to establish. Quantitation data may be useful in interpreting and corroborating STR typing results and for clearly illustrating them to the stakeholders.

Trace DNA Transfer in Co-Working Spaces: The Importance of Background DNA Analysis.

The presence of background DNA (bgDNA) can hinder the evaluation of DNA evidence at the activity level, especially when the suspect is expected to be retrieved due to their habitual occupation of the investigated environment. Based on real-life casework circumstances, this study investigates the prevalence, composition, origin, and probable transfer routes of bgDNA found on personal items in situations where their owner and person of interest (POI) share the same workspace. Baseline values of bgDNA were evaluated on the participants' personal items. Secondary and higher degree transfer scenarios of non-self DNA deposition were also investigated. The DNA from co-workers and co-inhabiting partners can be recovered from an individual's personal belongings. Non-self DNA present on the hands and deposited on a sterile surface can generate uninformative profiles. The accumulation of foreign DNA on surfaces over time appears to be crucial for the recovery of comparable profiles, resulting in detectable further transfer onto other surfaces. For a thorough evaluation of touch DNA traces at the activity level, it is necessary to collect information not only about DNA transfer probabilities but also about the presence of the POI as part of the 'baseline' bgDNA of the substrates involved.

Direct and Secondary Transfer of Touch DNA on a Credit Card: Evidence Evaluation Given Activity Level Propositions and Application of Bayesian Networks.

In a judiciary setting, questions regarding the mechanisms of transfer, persistence, and recovery of DNA are increasingly more common. The forensic expert is now asked to evaluate the strength of DNA trace evidence at activity level, thus assessing if a trace, given its qualitative and quantitative features, could be the result of an alleged activity. The present study is the reproduction of a real-life casework scenario of illicit credit card use by a co-worker (POI) of its owner (O). After assessing the shedding propensity of the participants, differences in DNA traces' qualitative and quantitative characteristics, given scenarios of primary and secondary transfer of touch DNA on a credit card, a non-porous plastic support, were investigated. A case-specific Bayesian Network to aid statistical evaluation was created and discrete observations, meaning the presence/absence of POI as a major contributor in both traces from direct and secondary transfer, were used to inform the probabilities of disputed activity events. Likelihood Ratios at activity level (LRα) were calculated for each possible outcome resulting from the DNA analysis. In instances where only POI and POI plus an unknown individual are retrieved, the values obtained show moderate to low support in favour of the prosecution proposition.

Genetic identification of endoscopic biopsies after unnecessary gastrectomy: Case report and medico-legal evaluation.

INTRODUCTION: Forensic genetic laboratories analyse samples included in paraffin to verify the genetic correspondence of histological samples, from living subjects or cadavers, in cases where there is a suspicion of contamination of samples with tissues of other patients. PRESENTATION OF THE CASE: A case of a man subjected to a gastrectomy as a result of a histological diagnosis of gastric adenocarcinoma after endoscopic biopsies is reported. The microscopic analysis on the gastric tissue after the gastrectomy excluded the presence of cancer. Having suspected a diagnostic error, a microscopic revision of the biopsies was performed and confirmed the presence of cancer cells but led to a hypothesis that there had been contamination with foreign intestinal tissue. The genetic analysis performed on various pieces of tissue, despite the reduced amount of biological material, succeeded in identifying the presence of two incomplete genetic profiles, one of which belonged to a subject of the opposite sex. DISCUSSION: The case raised many questions about the process of setting up histological specimens. Even though it is impossible to identify the healthcare professionals responsible for contamination, the organizational error during the management of biopsies has significantly affected the clinical case of the patient, who underwent a gastrectomy for cancer that was not present. CONCLUSION: This case is not simply an example of diagnostic error and related unnecessary surgery, but it has raised some doubts about patient management and it has led us to some medical-legal cause for reflection in the field of professional liability.

Medico-Legal Aspects of Pulmonary Thromboembolism.

Pulmonary ThromboEmolism (PTE) is an important disease for legal medicine. Because of their sudden lethal onset, generally medicolegal autopsies show few clinical information when PTE is the cause of death. During medicolegal autopsies, the autopsy operator must answer to important questions. For example, autopsy operator can need to assess the casual relationship between PTE and recent accident, such as trauma or long air travel. Furthermore, the autopsy operator needs to investigate the pathology of PTE as a cause of sudden cardiovascular death. It is relatively simple to confirm a fatal massive thromboembolus in the initial stage of thoracic investigations, but sometimes it might be difficult to distinguish this from postmortem clot. In such cases histopathological examination can help in the differentiation. Histological examination is also required for observation of chronological changes of the thrombi. Chronological evaluation is an important factor especially to determine whether the death coincides with the date of a specific accident/event or instead there is an earlier onset of PTE. In addition, histological sections sometimes show additional information, such as tumor fragments in cases of malignancy or small fragments of bone marrow in cases of active resuscitation, that can be useful in a medicolegal scenario. Furthermore, new diagnostic tools are arising, which they can be very helpful in the individuation of this frequently underdiagnosed disease. The goal of our work is to investigate these aspects through the review of the recent literature.