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The likelihood ratio paradigm of facial similarity score is the theory and method for interpreting the evidential significance of score finding from facial comparison. Facial similarity score likelihood ratio is the latest method of Bayesian likelihood ratio paradigm for forensic science. The likelihood ratio (LR) of facial similarity score is the ratio of the occurring probability of the facial score finding quantitatively assigned based on the probability distribution data of facial scores, under a pair of conflicting propositions that usually represent the claims of the prosecution and defense parties. The propositions typically deal with the question of whether a facial image with unknown identity collected at a crime scene comes from a suspect with known identity. The face score LR expresses the relative support direction and strength of the face score finding for the propositions of the prosecution and defense parties, providing quantitative evidence value for decision-makers to determine the disputed fact of the face source. The decision maker determines the fact of the facial source proposition based on the facial score LR opinion, or the posterior probability of the facial source proposition derived from the LR and the prior odds through Bayesian law, combined with other evidence, to exclude reasonable doubt. The likelihood ratio paradigm of facial similarity score is completely different from the traditional paradigm we are accustomed to in terms of scientific logic, opinion formation, expression, understanding, and reasoning applications. It also differs from the widely used LR paradigm of DNA feature findings, which poses new requirements and challenges for forensic examiner and decision-makers.
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Detecting abnormal behavior is crucial for maintaining public security, especially in densely populated critical areas. Traditional target detection algorithms often struggle to deliver satisfactory results under these conditions due to challenges like dense target distribution, significant scale variation, and complex backgrounds. YOLOv8 is one of the better perforing detection models effect among the object detection models. This study introduces a novel approach to improve detection accuracy by integrating advanced mechanisms into the YOLOv8 backbone network. Firstly, the coordinate attention (CA) mechanism is incorporated into the C2f module of the backbone network. This enhances the network’s focus on targets amidst complex backgrounds by emphasizing relevant features and suppressing noise. Secondly, the swin transformer model is integrated into the YOLOv8 backbone. The swin transformer facilitates greater information interaction across the feature map, effectively utilizing the background information and improving object detection accuracy under complex scenarios. The datasets used in the experiments are described, the evaluation indexes of P, R, AP and mAP are listed, and ablation experiments and comparative experiments are carried out. Experiments demonstrate the feasibility and effectiveness of these improvements. The enhanced network is compared with several mainstream networks, showing a significant improvement in average accuracy, reaching 95.1%. Compared to the basic network YOLOv8, the average precision has been improved by 2.4%, which proves the effectiveness of this method. In summary, the innovative integration of the CA mechanism and Swin Transformer model into the YOLOv8 backbone network addresses key challenges in detecting abnormal behavior in densely populated and complex environments. These enhancements lead to improved detection accuracy, making it a promising approach for public security applications.
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In this paper, the characteristics of corrosion traces on the surface of Q235 low carbon steel after being heated at 400 °C, 600 °C, and 800 °C for 15 minutes and the subsequent evolution of these corrosion traces at room temperature were investigated. Polyethylene (PE) was used as the smoke source, and a comparative study was conducted using macro and micro observation methods, color difference analysis, and other techniques to compare the non-corrosive smoke with the smoke generated from PE combustion. The results show that as the heating temperature increases, the oxide layer on the surface of the steel plate becomes coarser and the proportion of the oxygen (O) element increases. The presence of PE cembrstion gas has a significant influence on the high temperature corrosion of the steel plate. Following high temperature oxidation, the oxide skin on the non-flue gas exposed steel plate appears to be convex and pleated. As the temperature rises, the oxide skin gradually develops cracks and eventually peels off, displaying colors ranging from white to red and then to yellow. The steel plate surface exposed to PE pyrolysis atmosphere exhibits a dimming of its metallic luster and tends to become dark, green, and blue. This leads to the formation of a relatively dense and smooth oxidation layer compared to the non-cembrstion gas exposed steel plate. At 400 °C, the surface oxidation is non-uniform, displaying a more complex morphology compared to the non-cembrstion gas exposed steel plate. At 600 °C, the surface experiences significant discoloration; yet the oxidation is relatively smooth and uniform. At 800 °C, the heated surface becomes rough, with some areas showing convex oxides, but there is no evident blistering or shedding observed on the entire surface. With the increase of corrosion time at room temperature, the change of corrosion traces of the two steel plates at room temperature is relatively small, especially when exposed to PE smoke, the corrosion rate of steel plates at room temperature is partially inhibited.
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Footprint features, as one of the biological features of the human body, play an important role in the field of personal identification. At present, most research on footprint recognition focuses on footprint images as experimental data, using deep learning algorithms as the foundation and relying on auxiliary algorithms to complete high-precision footprint recognition tasks. However, there is a problem with models built on footprint images. Due to the similarity of footprints of different people, as the number of samples increases, the differences between the features of footprints of different people will continue to decrease, leading to an increasing false detection rate of the model. In order to reduce the interference of similarity between footprints on model recognition ability, this paper takes dynamic footprints as the research object and proposes a dynamic footprint retrieval method based on multi-class feature fusion. The proposed method uses a spatio-temporal fusion module to integrate the spatio-temporal information of footprints, so that the footprint recognition method is not limited to the apparent information of footprints. Firstly, the convolutional neural network is used to extract the frame level features of dynamic footsteps, and then the feature fusion module calculates the complete apparent features of the fused dynamic footprints through a trainable weight matrix and frame level features. Secondly, the temporal aggregation branch of the spatio-temporal feature fusion module is used to extract long-term temporal features within frame level features, and then the long-term temporal features are fused with frame level features through orthogonal fusion calculation method to form spatio-temporal features. Finally, the visual features and spatio-temporal features are fused for dynamic footprint retrieval. A comparative experiment is conducted on a dynamic footprint dataset of 200 people with existing deep learning algorithms, and the experimental results shows that this method achieved better performance, with Rank1 and mAP being 85.39% and 55.28%, respectively.
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Angle grinder is a tool used for grinding metal, wood, plastic and other materials. In recent years, it frequently appears in some cases of railway cabbe theft. Because the cutting marks formed by angle grinder are similar to saw tools, it is difficult to analyze and judge the types of tools in practical cases. In the paper, through simulation experiments, angle grinder and hacksaw were used to cut copper-core cables of different specifications, and the tool marks formed at the broken ends of cables were observed by microscope, to summarize the characteristics and differences of the tool marks formed by the two. It was found that the cross-sectional shapes of the cable broken end cut by angle grinder and hacksaw were similar overall, both of which were flat, but most of them were stepped by hacksaw, while those cut by angle grinder were smooth. Angle grinder will form parallel line traces with a certain radian at the section, while hacksaw will form multiple straight lines and cross each other. At the same time, there are differences between them in starting point trace, terminal trace and chip morphology. In actual case analysis, we should make a comprehensive judgment based on the cable broken end position, cable diameter and other conditions, and emphasize the differences in traces formed by angle grinder and saw tool. The research on the characteristics and formation mechanism of tool marks formed by tool marks formed by angle grinder cutting cables can provide certain theoretical support for judging the types of tools in related cases.
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This paper aims to validate the multiplex amplification system of 9 CpG sites reported in the literature, and explore its applicability in the Chinese population. The SNaPshot multiplex amplification system was validated in terms of accuracy, analysis of the initial amount of converted DNA templates, and detection of mixed samples. A total of 236 samples of five types of body fluids including saliva, semen, blood, vaginal secretion, and menstrual blood were selected. The SNaPshot multiplex amplification system was used to detect the methylation values of 9 CpG sites. The detection threshold of CpG sites was that the methylation value is greater than 0.1. Analyze the starting amount of transformed DNA templates in this system after converting DNA using sodium bisulfite (template amount ranging from 0.5 ng to 10 ng). DNA extracted from four body fluids, including saliva, semen, blood, and vaginal secretion, were mixed in the following ratios: 1∶1, 1∶5, 1∶10, and 1∶20. Finally, the detection data set of 232 samples of the five types of body fluids was used to optimize the existing body fluid source determination method. The train set (n=162) was used to construct a random forest model, and the test set (n=70) was used to predict the body fluid type and evaluated the predictive performance of the model. Furthermore, an external data set (n=40) was added to validate the prediction model. In saliva, semen, blood, vaginal secretion samples, and menstrual blood, the body fluid type was determined directly based on the specific sites of body fluids, and the accuracy rates of body fluid identification were 100%, 98%, 98%, 94% respectively. Due to the influence of the menstrual cycle, some sites were missing, and the average accuracy of menstrual blood identification was 21%. This system could effectively detect the amount of transformed DNA from 1 ng to 10 ng. Among the mixed sample, both body fluid sources were correctly identified in all 1∶1 mixed samples. The main components could be detected in the other mixed samples (ratio 1∶5, 1∶10 and 1∶20), while there was a significant difference in the detection of secondary components. A random forest model was built from 232 samples, and the accuracy of identifying the five fluid sources in both the test and validation sets was 100%. The above results show that the multiplex amplification system has high accuracy for the identification of saliva, semen, blood and vaginal secretion, and is suitable for the identification of trace samples, mixed samples (ratio 1∶1) or main components of other ratios. Compared with direct interpretation based on body fluid specific peaks, the new random forest model can better identify menstrual blood. In summary, the multiplex amplification system for tissue identification of five types of forensic body fluids based on DNA methylation is potential for good forensic application.
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In order to study the feasibility of using fluorescein to develop latent blood fingerprints based on fluorescent labeling technology and explore the optimal conditions for its development, we selected two cselected used fluoresceins (FITC fluorescein and DCFH-DA fluorescein) as the main research objects of this experiment, to design the method and procedure of developing latent blood fingerprints on non-porous surfaces with fluorescein, based on the principle of fluorescent labeling technology. On this basis, PBS buffer was used to change the pH environment of fluorescein solution, and acetone was used to dilute the two fluorescein solutions by 5 times, 10 times and 100 times, respectively, in order to explore the best developing conditions of latent blood fingerprints. The results showed that both FITC fluorescein and DCFH-DA fluorescein were effective in developing latent blood fingerprints on non-porous surfaces. The best conditions for FITC fluorescein to develop latent blood fingerprints on non-porous surfaces are: the developing time being 10 minutes, the pH environment value being 9.35, and the concentration being the original concentration; The best conditions for DCFH-DA fluorescein to develop latent blood fingerprints on non-porous surfaces are: the developing time being 20 minutes, a pH environment value being 13.01, and the concentration being the original concentration. Therefore, it is feasible for the fluorescence labeling technology to develop latent blood fingerprints on non-porous surface, but it is still necessary to further explore the preservation time of prepared fluorescein solution and the damage of DNA detection in blood fingerprints by this technology, and comprehensively analyze its practical application value.
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This paper aims to establish a solid-phase support liquid-liquid extraction-high performance liquid chromatography/triple quadrupole tandem mass spectrometry (SLE-HPLC-MS/MS) method for the detection of scopolamine, anisodamine and atropine in blood and urine. The effects of protein precipitated method, solid phase extraction method and solid-phase supported liquid-liquid extraction method on the extraction of drugs from blood and urine samples were investigated. Scopolamine, anisodamine and atropine, in blood and urine samples were analyzed by high performance liquid chromatography triple quadrupole tandem mass spectrometry. The results showed that the recovery rate of solid-phase supported liquid-liquid extraction was the highest. The linear relationship between the concentration of scopolamine, anisodamine and atropine in blood and urine and the peak area (r>0.999 2) was good in the range of 0.1－100 ng/mL (blood) and 0.5－100 ng/mL (urine). The minimum detection limit of scopolamine, anisodamine and atropine in blood was 0.01 ng/mL, and the quantitative limit was 0.1ng/mL; The minimum detection limit of scopolamine, anisodamine and atropine in urine was 0.05 ng/mL, and the quantification limit was 0.5 ng/mL. The solid-phase supported liquid-liquid extraction liquid chromatography/tandem mass spectrometry method is characterized by simple operation, less solvent usage and high recovery rate. It is suitable in the detection of scopolamine, anisodamine and atropine in blood and urine for three types of drug poisoning cases (incidents).
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The means and forms of drug transmission are becoming increasingly diverse, posing significant challenges to public security investigations, laws and regulations supervision, and identification technology. In terms of identification technology, the detection of isomers, which can easily lead to misjudgments, remains particularly challenging. The comprehensive analysis of multidimensional detection methods has emerged as a trend in addressing the identification and regulation of new psychoactive substances. Currently, a notable synthetic cathinone called 2-dimethylamino- 1-[3,4-(methylenedioxy)phenyl]-1-pentanone(N,N-dimethylpentylone) warrants attention. This paper aims to develop an analytical method for identifying N,N-dimethylpentylone as a new synthetic cathinone. The processed unknown samples are analyzed using a combination of gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), nuclear magnetic resonance (NMR) including 1H-NMR, 13C-NMR, H-H COSY, HSQC, HMBC, and Fourier transform infrared spectroscopy (FTIR). GC-MS analysis results show that the qualitative ion fragments are m/z 100.1, m/z 58.1, m/z 121.1, m/z 149.0, with a retention time at 11.888 minutes. LC/MS analysis results show that the parent ion is m/z 250.05, and the product ions are m/z 100.10, m/z 205.10, and m/z 135.10, with a retention time at 9.772 minutes. FTIR analysis results show that there area carbonyl absorption peak at 1 676 cm-1, and a benzene ring vibration absorption peak at 1 506 and 1 441cm-1. One-dimensional nuclear magnetic spectrum results show 9 hydrogen signals with different chemical shifts and 14 carbon signals with different chemical shifts in the unknown compound. Two-dimensional NMR analysis results show that the unknown compound conforms to the structure of N,N-dimethylpentylone. In summary, N,N-dimethylphenylone components are detected in the unknown sample.
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Postmortem interval (PMI) refers to the interval between the discovery or examination of the body and the occurrence of death. Estimation of postmortem interval is one of the important research contents in forensic pathology，and it has always been the focus and hot spot of research work. Different techniques are used to evaluate and analyze the changes in the human body after death to estimate postmortem interval. The traditional methods of estimation of postmortem interval are based on postmortem phenomena such as algor mortis, rigor mortis, livor mortis, etc. These methods rely on the subjective experience of forensic pathologists, and the estimated time of death is a relatively wide range, and the estimated result is susceptible to subjective judgment. In recent years, postmortem computed tomography (PMCT) has become increasingly influential in the field of forensic pathology. Postmortem computed tomography is a non-invasive, rapid, and objective auxiliary means of autopsy, which can significantly improve the quality and efficiency of autopsy and can find imaging features that may not be observed in traditional autopsy. After the death of the human body, the body will undergo a series of postmortem changes according to a certain time law. A series of characteristic imaging changes in cadaver organs and tissues with the passage of time of death can be observed through the application of postmortem computed tomography, and these imaging changes can be quantitatively and objectively described, The potential ideal imaging indicators can be used to estimate postmortem interval and the correlation between these indicators and the postmortem interval can be analyzed. This paper systematically reviewed the research on the correlation between postmortem imaging features of organs and tissues (such as brain, heart, aorta, lung, liver, etc.) after postmortem computed tomography of various parts of the cadaver (head, chest, abdomen) and the estimation of postmortem interval, in order to provide new ideas for the study of the estimation of postmortem interval and further expand the application of virtual anatomy technology in the field of forensic pathology.
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Dried blood spot (DBS) is a sampling technique in which a small volume of blood is collected on a specific type of filter paper. Since the 1960s, DBS has been primarily used for the newborn screening of metabolic diseases. With the development of highly sensitive analytical instruments, the dried blood spot technique allows for accurate quantification of ethanol, stimulants, drugs of abuse and heavy metal elements in biological samples. Due to its obvious advantages, the application of DBS in forensic toxicology has witnessed significant growth in the past decade, which is highlighted and presented in this article. Some challenges and suggestions of dried blood spot applications were summarized for the further research as well.
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This study uses the Web of Science Core Collection as its search dataset, employing the visualization tools VOSviewer 1.6.20 and CiteSpace 6.2R6 to analyze 509 publications related to the statistical quantification of trace evidence, spanning 57 countries, 976 institutions, and 267 journals. The study examines key literature nodes from four perspectives: publication volume, publication outlets, keyword co-occurrence, and keyword clustering, providing researchers with a comprehensive and intuitive understanding of the research trends and emerging hotspots in the field. The findings reveal that over the past decades, the volume of research on statistical methods for trace evidence has shown fluctuating growth. European countries have shown significant collaboration on this topic, forming a closely-knit regional cooperation network, with the Netherlands Forensics Institute being the most prolific institution. Fingerprints are a crucial subject of statistical quantification of trace evidence, with statistical and quantitative methods primarily focusing on a series of methods based on Bayes’ theorem, such as likelihood ratios and Bayesian networks. A trend in research hotspots is observed, transitioning from clusters of subjective quantification methods (such as subjective likelihood ratios) to objective ones (such as feature-based and score-based likelihood ratios). Current challenges in the statistical quantification of trace evidence include difficulties in interpreting high-dimensional data, model error rates, and model parameter estimation. The study suggests improvements such as establishing quality assessment metrics for high-dimensional evidence, developing models with dynamically adjustable error tolerance, employing multiple validation and evaluation strategies, and fostering expert consensus on new paradigms in trace evidence.
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Currently, capillary electrophoresis-based Y-STR genotyping kits can detect up to 40 Y-STR loci simultaneously. However, these kits only report length-based genotypes and are unable to provide STR sequence information. The STRSeqTyperY68 kit, designed for forensic male pedigree differentiation using next-generation sequencing technology, excels at genotyping 67 Y-STR loci plus a sex-determinant locus in a single-tube reaction on the MiSeq FGx sequencing platform. It simultaneously provides both length and sequence polymorphism genetic information, simplifies testing procedures, enhances efficiency, and facilitates precise differentiation of male family lineages. The ITO method is commonly used to calculate the kinship index of two individuals’ biological relationship based on Mendel’s law of genetic segregation. Additionally, it evaluates consanguineous relationships within five degrees of kinship between two individuals. The combination of next-generation sequencing technology and the ITO method can effectively narrow down the range of potential families. This paper documents a rape and murder case that remained unsolved for eight years. By cooperatively utilizing the STRSeqTyperY68 kit and the ITO method, the potential connection between crime scene evidence and reference samples was evaluated. Gradually, the investigative leads were narrowed down, leading to the resolution of the case.
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In this study, we report a three-step mutation at D8S1132 locus between an alleged father (AF) and child in a paternity case. Three autosomal STR multiplex amplification kits were used for capillary electrophoresis detection. At the D8S1132 locus, the genotypes were: alleged father 17/23, parent mother 22, and child 20/22, which does not comply with Mendelian inheritance laws. Paternity was confirmed by calculating the cumulative paternity index and a three-step mutation was identified at the D8S1132 locus. Next-generation sequencing was further used to validate the experimental results and explore the source of the mutation. The results indicated that the allele 20 of the child was derived from the allele 23 of the alleged father. In addition, next-generation sequencing platform that simultaneously detected different genetic markers such as STR, SNP, and mitochondria DNA increased the cumulative parental index, which further confirmed the paternal relationship. Therefore, this case suggests that in paternity testing, when multiple mutations occur at a certain STR locus, capillary electrophoresis and next-generation sequencing can be combined for cross-validation to improve the credibility of the identification results.
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This article reports a case of death due to traumatic vertebral artery rupture caused by blunt force trauma to the head and face. We utilized the cutting-edge optical microscopy technology of a super-depth three-dimensional microscopy system (super-depth microscope) to examine minute tears in the arterial wall and identify the source of bleeding, which aids in case classification. This method offers significant advantages in accuracy, speed, and visual clarity, addressing the shortcomings of traditional examination methods to traumatic vertebral artery rupture and greatly meeting the demands for swift investigation and identification in today’s legal system. The article also discusses the injury mechanisms, key identification points, and considerations for similar cases, providing a reference for determining the cause of death and the nature of cases involving traumatic subarachnoid hemorrhage at the base of the brain.
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Injuries caused by animals are relatively common in forensic examinations, but those resulting from bird pecking are less frequent. In particular, eyeball injuries caused by bird pecking are even rarer. Such injuries can easily be mistaken for human-inflicted injuries, leading to misunderstandings among the deceased’s family members and even forensic personnel. This can cause the case to reach an impasse or even trigger petitions. This article presents a case of ocular perforating defects caused by bird pecking, aiming to introduce the characteristics of animal injuries and the specific features of injuries caused by bird pecking, as well as how to analyze and evaluate such injuries, thereby providing a basis for determining the nature of the case.
