UV-Visible spectroscopic effect on Haemoglobin & DNA degradation: A forensic approach

Comparison of gender identification using exfoliated cells obtained from toothbrush and miswak: A longitudinal study

Gender identification plays a pivotal role in forensic medicine. Among the various methods used for gender identification, deoxyribose nucleic acid (DNA) based methods are considered accurate. Exfoliated oral mucosal cells that are harvested from oral hygiene aids can be potentially used for gender identification using real-time polymerase chain rection (PCR). The aim of the present longitudinal study is to assess and compare the efficacy of toothbrush and miswak as potential tools to harvest exfoliated cells for gender identification. Forty healthy volunteers were recruited and asked to clean their teeth using new toothbrush and fresh miswak each day for 4 days. Toothbrush and miswak used by the participants were subjected to DNA analysis immediately, 1st, 2nd and 6th month. The absorbance of DNA samples were quantified and gender identification was done by amplification of sex determining gene-Sex determining region Y gene (SRY) and ALT1 genes using real-time PCR. The number of correct and positive identification for samples at various time points were tabulated and subjected to statistical analysis. Post hoc power analysis showed that the study had a power of 93%. Correct and positive gender identification was observed for the samples (100%) obtained using miswak, for tooth brush it reduced to 95%, 80%, and 35% at the end of 1st, 2nd, and 6th month. The differences seen at the end of 2nd month and 6th month were statistically significant. Miswak is a better tool to harvest exfoliated cells for gender identification when compared to a toothbrush. Hence, miswak can serve as a potential tool in forensic medicine for DNA extraction and subsequently victim identification.

Alkaline Phosphatase for Estimating the Time since Deposition of Blood Fingerprints by Scanning Electrochemical Microscopy

Blood is one of the most frequent and valuable traces encountered at crime scenes, where knowing the time since deposition (TSD) of bloodstains tremendously assists forensic experts to screen out crime-related evidence and aids in the reconstruction of the event sequence. Although increasing proof-of-concept methodologies for investigating the TSD of bloodstains have been reported, there is still no accepted strategy in forensic practice as the aging mechanism involves complex components, leading to the inaccuracy of the estimation results. Herein, an endogenous biomarker of alkaline phosphatase (ALP) was chosen to investigate the TSD by scanning electrochemical microscopy (SECM). Results demonstrate that the ALP activity acquired via SECM lateral scan assay exhibited a clear decrease over time, and a similar trend was observed on both poly(vinylidene fluoride) (PVDF) membrane and glass, with the aging kinetics on PVDF membrane being faster than glass. By means of quantitatively calculating the flux of generated p-aminophenol (PAP), we established the aging curve and realized the TSD estimation of blood fingerprints (BFPs) that was unable to be distinguished via optical measurements. Intriguingly, the as-obtained estimation accuracy ranged from 74.6 to 93.7%, proving the possibility of using an ALP biomarker and SECM. More appealingly, the predicted TSDs were capable of accurately differentiating the deposition sequence of overlapping BFPs, which was hardly achieved by optical means. Therefore, this proof-of-concept strategy demonstrates the value of SECM as a forensic tool and opens possibilities for revealing multidimensional information about crime.

Discovery and validation of metabolite markers in bloodstains for bloodstain age estimation

Bloodstain age estimation involves measuring time-dependent changes in the levels of biomolecules in bloodstains. Although several studies have identified bloodstain metabolites as markers for estimating bloodstain age, none have considered sex, age-related metabolomic differences, or long-time bloodstain age. Therefore, we aimed to identify metabolite markers for estimating the age of bloodstains at weekly intervals within 28 days and validate them through multiple reaction monitoring. Adenosine 5'-monophosphate, choline, and pyroglutamic acid were selected as markers. Seven metabolites were validated, including five previously reported metabolites, ergothioneine, hypoxanthine, L-isoleucine, L-tryptophan, and pyroglutamic acid. Choline and hypoxanthine can be used to differentiate bloodstains between days 0 and 14 after deposition at weekly intervals, whereas L-isoleucine and L-tryptophan can help distinguish bloodstains between 7 days before and 14 days after deposition. Evaluation of the changes in metabolite levels according to sex and age revealed that the average levels of all seven metabolites were higher in women on day 0. Moreover, the level of ergothioneine was significantly higher in elderly individuals than in young individuals at all time points. In this study, we confirmed the potential effectiveness of metabolites in bloodstains as forensic markers and provided a new perspective on metabolomic approaches linked to forensic science.

Internal standard metabolites for estimating origin blood volume of bloodstains

The volume of blood leaked from blood vessels may change due to evaporation of water under the natural influence of the external environment. Bloodstains and dried blood spots (DBS), which describes blood dried in the external environment, are similar in their production and their metabolite quantification profiles. In both bloodstain metabolite analysis in the forensic science field and DBS metabolite analysis in the clinical field, it is important to determine the volume of the origin blood as this affects metabolite quantification results. Therefore, the purpose of this study is to discover the internal standard metabolites that have quantitatively proportional relationships with origin blood volume and maintain constant concentrations even as the age of the bloodstain increases. As a result, the concentrations of L-isoleucine and L-phenylalanine increased in proportion to the origin blood volume of the bloodstain. The differences in concentration of L-isoleucine were significant in all volume comparisons except in the comparison between 65 μL and 85 μL. The differences in concentration of L-phenylalanine were significant in all volume comparisons except between 65 μL and 45 μL and between 65 μL and 85 μL. In addition, it was confirmed that both metabolites tended to maintain constant concentrations without being affected by bloodstain age as the volume became smaller. These internal standard metabolites can be used for estimating the origin blood volume of bloodstains during metabolite analysis of bloodstains and DBS and could provide a volume criterion for standardization when comparing metabolite quantification between samples.

Bloodstain Metabolite Markers: Discovery and Validation for Estimating Age of Bloodstain within 7 Days

Metabolomic research using analytical chemistry methods has been carried out in a wide range of research fields. However, research combining forensic science and metabolomics is rare. Determining the age of bloodstains could provide key information regarding when a crime was committed. Currently, validated methods for estimating the age of bloodstains are unavailable. Metabolites are intermediate and final products of chemical reactions. Therefore, they are less likely to be degraded than other components of blood under field conditions. In this study, metabolites in bloodstains were analyzed using liquid chromatography-mass spectrometry to discover and validate metabolic markers for determining the age of bloodstains within a week post-bleeding. Nontargeted analysis of bloodstain metabolites revealed statistically significant differences over time. Quantitative analysis of identified candidates via multiple reaction monitoring confirmed the statistical significance according to the age of bloodstain. Pyroglutamic acid, l-glutamine, acetylcarnitine, and adenosine 5'-monophosphate were selected as the final markers. The content of each marker exhibited a statistically significant and consistent tendency to decrease with the age of bloodstain. Furthermore, the effect of hemolysis was considered according to the blood fraction spots of the four markers. This study is the first to identify and validate metabolite markers that may help determine the age of bloodstains within a week post-bleeding. If applied to crime scenes as indicators of the age of bloodstains, they can be used as innovative and important tools for reconstructing crime scenes, suggesting initial investigative direction. This study highlights the forensic utility of blood metabolites ex vivo.

Evaluating Time-Dependent Extraction of Exfoliated Oral Mucosal Cells from Used Toothbrushes and Miswak

An integral part of forensic work is DNA quantification and profiling, which necessitates many highquality samples for good results. Oral mucosal cells have become an essential source of genomic DNA in epidemiological studies. The time of collecting DNA samples is a critical factor in forensic science. To compares the time-dependent extraction of DNA yield and purity from exfoliated oral epithelial cells from toothbrushes and miswak used for time intervals up to 5 months. Thirty healthy volunteers were given toothbrushes and miswak to use for six days. The used toothbrushes and miswak were collected, stored at room temperature, and analyzed immediately and at the end of the first, second, third, fourth, and fifth months. Comparisons between the two independent groups of toothbrush and miswak were done by an independent two-sample t-test. The changes over time for each outcome were analyzed using repeated-measures ANOVA. DNA yield of the exfoliated oral epithelial cell samples was higher from female samples, while DNA purity was higher in the male samples. The Miswak contained a sufficient amount of DNA similar to toothbrushes. The yield and purity are not significantly altered by storing them for at least five months at room temperature.

Medico-legal evidence collection in child sexual assault cases: a forensic significance

Background

Every year, millions of children face sexual exploitation worldwide. In India, 109 children (National Crime Records Bureau2018) were sexually abused everyday (22% jump from the previous year). Even with advanced DNA techniques, the conviction rate remains low. The methods used for forensic DNA evidence analysis vary around the world, but the primary step of biological evidence collection plays the most vital role. Proper and timely evidence collection from the victim by a trained medical professional is important.

Main body

Dynamics of child sexual assault being massively different from an adult rape demands altogether different approach of evidence collection. A standard sexual kit employed for evidence collection needs urgent modifications considering genital development of pre- and post-pubertal victims. In the present study, parameters including systemic collection and evaluation of forensic evidences, medico-legal examination, and developmental consequences of sexual assault on pre-pubertal victims were assessed. Further suggestions for separate evidence collection kit during medico-legal examination were given for pre-pubertal victims and alleged accused in sexual assault cases in order to streamline and for better evaluation of DNA analysis in forensic laboratories.

Conclusion

The importance of expert medical practitioners plays a significant role in collection of appropriate information and evidences from the victim of sexual assault. General guidelines for evidence collection in sexual assault cases are not well suited for pre-pubertal victims. Appropriate reforms pertaining to the age and genital development of victims are required. Securing clothing as forensic evidence is essential in most cases as it turned out to be the exclusive evidence bearing material. The purpose of this article is to bring awareness about the thorough medical examination and modified sexual assault kit for pre-pubertal victims and alleged accused for a better approach in evidence collection and conviction rate.

DNA Transfer in Forensic Science: Recent Progress towards Meeting Challenges

Understanding the factors that may impact the transfer, persistence, prevalence and recovery of DNA (DNA-TPPR), and the availability of data to assign probabilities to DNA quantities and profile types being obtained given particular scenarios and circumstances, is paramount when performing, and giving guidance on, evaluations of DNA findings given activity level propositions (activity level evaluations). In late 2018 and early 2019, three major reviews were published on aspects of DNA-TPPR, with each advocating the need for further research and other actions to support the conduct of DNA-related activity level evaluations. Here, we look at how challenges are being met, primarily by providing a synopsis of DNA-TPPR-related articles published since the conduct of these reviews and briefly exploring some of the actions taken by industry stakeholders towards addressing identified gaps. Much has been carried out in recent years, and efforts continue, to meet the challenges to continually improve the capacity of forensic experts to provide the guidance sought by the judiciary with respect to the transfer of DNA.

Evaluation and SNP typing of DNA from ultraviolet-irradiated human bloodstains using TaqMan assay

When detecting DNA profiles from forensic materials, it is pivotal to know the extent of degradation and which DNA marker can be genotyped. Ultraviolet (UV) is one of the common external factors that causes DNA damage, through which, an attempt to reveal cardinal genetic information can be made. In this study, after irradiation with three different UV wavelengths, UV-damaged DNA in the bloodstains was analyzed with long and short TaqMan assays using real-time PCR. In addition, both short tandem repeat (STR) profiles and single nucleotide polymorphisms (SNPs) from the damaged DNA at different stages of UV exposure were also assessed. With increasing in UV irradiation cycles, there was a delay of the amplification curves accompanied with a decrease in the DNA amounts collected. Despite the amplification of STR genotype was not altered after 75 cycles of UVC irradiation, all 12 SNP loci could still be detected. Furthermore, a short-assay line was detected in the absence of an amplification of the evaluation curve. The results indicate that, although the DNA template might not be useful and suitable for analysis of STR profile, this approach is of some values in detecting SNPs.