In October 2021, the Anti-drug Detachment of Wenzhou Public Security Bureau seized a package of yellow substances suspected of drugs in the adjacent sea area, and the case handling unit sent the yellow substances for inspection. To detail the composition of the sample and the structure of the main compound in the sample, it was analyzed by ultra-performance liquid chromatography tandem high resolution mass spectrometry (UHPLC-HRMS), nuclear magnetic resonance (NMR) and Fourier transform infrared spectrometer (FTIR). Initial testing indicated that the main compound of the sample was not matched in our in-house database, which prompted us to deeply analyze the unknown compound by different analytical techniques. The analysis of UHPLC-H RMS provided the precise mass quantity of the unknown compound with a mass accuracy of 2.5 ppm. The characteristic ions (m/z) were 125.0151, 179.0619 and 207.0567, close to those of ketamine, which indicated that the compound may be the analogue of ketamine. Proposed fragmentation mechanism is also present. Further analyses by 1H NMR, 13C NMR, 15N-NMR, distortionless enhancement by polarization transfer spectroscopy (DEPT 135°), proton two-dimensional correlation spectroscopy (1H-1H COSY), heteronuclear single-quantum correlation spectroscopy (HSQC), heteronuclear multiple bonding connectivity spectroscopy (HMBC) detailed the structure of the analogue. 15N-NMR confirmed the presence of nitro-group. DEPT pulse sequence utilized for the assignment of the different types of carbons showed that there were four methylene carbons and a quarternary carbon presented in the molecule of the unknown. Assignments were made via 1H NMR and 13C NMR, assisted by 1H-1H COSY, HSQC, and HMBC. IR has determined the type of such functional groups as carbonyl, nitryl, and chemical bonds of C and Cl by the related absorption characteristics. It was confirmed that the yellow powder was a new precursor 2-(2-chlorophenyl)-2-nitrocyclohexanone. According to the literature, it was found that it could be used to synthesize ketamine. It is the first time of this substance to be detected in suspected drugs in China. However, in recent years, the clinical interest in ketamine has increased due to its positive impact in treating depression and the rapid onset of its antidepressant effect. It led to an increase in publications of the procedure of the synthesis of ketamine, which may be used for illegal synthesis. 2-(2-chlorophenyl)-2-nitrocyclohexanone is an essential precursor of the new synthetic ketamine process for criminals to evade the attack, providing a reference for the control of precursor chemicals and the inspection of related cases in the future.

In the investigation of telecom fraud dens, it is a key link to investigate the electronic equipment involved and extract electronic data, and the on-site evidence collection of memory data is an essential part of it. The scene of telecom fraud dens is usually complex and diverse, which commonly does not have the conditions to use large-scale forensics equipment. At the same time, there are numerous types and quantities of equipment involved, and the time for forensics is tight, which brings great technical difficulties and challenges to the scene forensics of memory data. Based on the relevant principles in “General Method for Collecting Electronic Evidence Data on the Spot”, this paper studied the current situation of memory data extraction in on-site evidence collection of telecom fraud dens. Firstly, according to the actual needs of the scene investigation of telecom fraud dens, the memory extraction methods of Windows, MAC and Linux systems in normal state were introduced. Then, for some troublesome problems, from the mechanism of operating system hibernation and unexpected system crash, the influence of hibernation files and dump files on memory extraction was analyzed, and the memory extraction method without knowing the password was proposed by using DMA dynamic memory reading technology. Finally, based on the characteristics of memory extraction in den investigation, a scheme of scene memory forensics was proposed and applied to practical cases, which provided reference for the exploration and evidence collection of such cases.

This study is intended to provide a visual and quantifiable auxiliary technology for analysis of rib fracture injury mode. The rib fracture caused by boxing and chest compression is simulated by the finite element method: (1) The fist model is set to hit the left chest of THUMS4.02 (Total Human Model for Safety 4.02) at the speed of 6m/s. (2) The pressing hammer model is set to presses the precordial region of THUMS4.02 with a vertical downward force of 400 N. Distribution and morphology of rib fractures shown by the simulation results were compared, and the injury mechanism of the two was analyzed from the perspective of biomechanics. The simulation results are compared with those reported in the literature. The simulation results show that: (1) Shape and distribution characteristics of rib fractures: the shape of the broken ends of rib fractures caused by boxing is inward bending, and the fractures are distributed at the direct hitting positions of the ribs. The shape of the broken ends of rib fractures caused by chest compression is outward bending, and the fractures are distributed in the nondirect stress areas of the ribs. (2) Biomechanical response characteristics: when boxing the chest, the strain is concentrated in the position of the boxing ribs. Compressive stress is generated on the outer side of the rib at the striking position, and tensile stress is generated on the inner side. When pressing the chest, in addition to the strain distribution at the pressing position, there is another obvious strain distribution at the front line of the rib axillary on the pressing side of the chest. The lateral surface of the rib at the axillary front line generates tensile stress, and the medial surface causes compressive stress. The literature supports the simulation results, suggesting that the finite element method can be used to realize visual and quantifiable auxiliary analysis and interpretation of the injury mode of rib fracture.

To comprehensively understand the current situation and problems of the development of trace evidence specialty in criminal technology identification organizations in China, and put forward countermeasures and suggestions, a questionnaire was designed to investigate the construction of trace evidence laboratories in China. 307 provincial, municipal, district and county-level criminal technical identification organizations that carried out physical and chemical tests in 31 provinces, autonomous regions, and municipalities directly under the Central Government (excluding Hong Kong, Macao, and Taiwan) were investigated with the Questionnaire Star. The results of the questionnaire were analyzed with statistical methods. The 307 criminal technology identification organizations involved in the investigation included 31 provincial, 261 municipal, and 15 district/county-level, including 121 that passed the national laboratory accreditation (CNAS) and 186 that hadn’t passed the CNAS accreditation; 304 have passed the qualification certification, and 3 haven’t passed the qualification certification. All the criminal technical institutes involved in the investigation have set up physical and chemical testing laboratories, and the vast majority (301, accounting for 98.0%) have not set up a special trace evidence department. 224 organizations carried out the examination of trace evidence, accounting for 73.2%. There are 1 463 technicians in 307 laboratories, with an average of 4.77 in each laboratory. The professional and technical personnel are mainly chemical and related majors, accounting for 65.0%. GC-MS and GC are the most commonly used physical and chemical analysis instruments, with 409 and 3 457 sets respectively. The common analysis equipment for trace evidence specialty, such as scanning electron micro-scope/energy dispersive spectrometer (SEM-EDS, 63 sets) and infrared spectrometer (IR, 117 sets), account for a relatively small proportion. Accelerants and fire residues, explosives and post-blast residues, paints, gunshot residues and fibers are the most commonly encountered evidence. The training of professional and technical personnel is the most important factor restricting the development of the trace evidence specialty. Research has found that there are some problems in the development of the trace evidence specialty in China, including the weak awareness of the discovery, collection and application of trace evidence, the relatively backward laboratory equipment, the imperfect technical system of trace evidence examination, and the relatively lagging information system construction. The trace evidence laboratory has entered the stage of comprehensive construction in China. The development of trace evidence specialty in China can be promoted by clarifying the professional boundaries of trace evidence, building regional trace evidence laboratories, improving the technical method system of trace evidence, strengthening technical exchanges, training and promotion, and strengthening the training of trace evidence professionals.

The paper aims to provide the reference and pathological data for the determination of the poisoning caused by heartbreak grass. Post-mortem examination, histopathological examination, and toxicological examination were performed on a deceased case of gelsemium elegans poisoning caused by ingestion of homemade Chinese medicine, and the tissue cells were stained and observed with microscope for pathological examination, while liquid chromatography mass spectrometry (LC-MS) was used for toxicological examination of heart blood and the residue of Chinese medicine. The relevant literature on gelsemium poisoning was reviewed，such as the poisoning symptoms，pathological feature and postmortem content of gelsemium in blood or tissue. Although many poisoning cases were reported, most of them were published by medical and health departments, and post-mortem toxicological data are scarce. This paper reported a dead case which gelsemine, koumine and gelsecine were detected in the heart blood with the concentration of 77.4, 30.3 and 37.1 ng/mL respectively, and the pathological examination showed that the SA node artery stenosis and myocardial fibrosis were found, but on typical toxic characteristics in tissues were observed. In this case of acute poisoning of Gelsemium elegans, no typical features were found by autopsy, but the obtained basic data such as toxin concentration in blood contributed to accumulate forensic toxicological data of Gelsemium elegans poisoning, and provided a reference for forensic toxicologists in identifying the cause of death in related cases.

There are few morphological methods for fingerprint age analysis, and it is not certain that the mastoid line morphology of fingerprint is correlated with age. Through statistical and correlated analysis of quantifiable feature information, it is found that the number of wrinkles and fine line, the density of mastoid line, the width of mastoid line and small furrow, and other indicators are correlated with age, but the use of these indicators is not enough to analyze the age of the hand imprint remnant. The purpose of this paper is to study the performance characteristics of fingerprints in different age groups, especially the age-related characteristic information that is difficult to be quantified in fingermarks at the present stage, such as the fuzzy phenomenon of fingermarks, the symmetry degree of the edge of friction ridges, and the change rule of sweat holes with age. We explore the specific method of age analysis by fingerprints through observing and summarizing. The fingerprints were observed through the microscope, and the typical examples were visually displayed by fingerprint atlas. Fingerprints are extracted from a large number of samples and represent the characteristics of most samples of the corresponding age. In this paper, the characteristics and performance of different age groups are introduced through text, and the characteristics of fingerprinting performance in different age groups are displayed more intuitively and vividly with the fingerprint atlas. After observing a large number of fingerprint samples in different age groups in the fingerprint archives, the morphological characteristics of fingerprint in different age groups were summarized, and the specific steps and methods of age analysis are preliminarily formed. The specific process of such analysis was showed in combination with practical cases. The map of fingerprint contains the various typical and atypical manifestations of the fingermark samples at the corresponding age. Detailed steps are proposed for a morphological method of age analysis using handprints, which, like a code of practice, can be used by an experienced fingerprint analyst to make a preliminary estimate of the age of the person left behind. This paper provides a direction for researching fingerprint-based age analysis.

Facial comparison is often required and carried out for forensic purpose. Such an operation relies on the morphological analysis and evaluation into facial features. Therefore, there is the necessity to deploy in-depth researches on facial features, especially the individual ones. An evaluation approach was tried in this paper of focusing on the individual features (pigments, moles, and other specifics) in facial images. Through statistical analysis of the individual features from the facial image dataset of open source, calculations were performed about the probabilities of individual features appearing on facial images and/or even at some specific sites under the same identity and/or different ones. Subsequently, the individual features were meausred of their matching values by likelihood ratio manipulation: the probability ratio of individual features appearing in a specific location under the above set two conditions. With the facial data resolution in this experiment, the likelihood ratio was able to reach the level of 104 in relation to a single facial individual feature being matched, and even exceed 1 billion with matching two facial individual features - a digital magnitude supporting the confirmative conclusion of same source/identity. The facial images adopted in this paper hold a resolution of 178×218, the size of the facial area is accordingly about 120×150. The resolution utilized with this research is believed to be ideal for facial image comparison to match the appearing area according to the individual features. If resolution-higher facial images are available, the results rendered from this research may serve as a lower threshold. The facial images used for this research are from public dataset with different imaging conditions, displaying the face images of different race, gender and age characteristics among the number of IDs (identities) of 10 177. Although the public dataset tested with this research attains such a scale, a question is still open to answer about whether the distribution of its contained facial individual features and rendered matching can represent a wider range of facial data.

Recordings made by mobile phone are a common form of evidence in current litigation, but it is easy to separate recording files from their initial equipment, so the evidence review of originality and integrity of recordings is prone to cause disputes, which often need to be resolved through judicial expertise. However, the current achievements mostly focus on the integrity identification of mobile phone recordings and the equipment appraisal of IOS recording files. For the research on the traceability analysis of Android recording files, there is still a lack of research results. Because of this, we selected several Huawei and Xiaomi smartphones, simulated the typical operation behaviors such as recording, deleting, collecting, and transferring ordinary recordings and call recordings, and proposed a method for recording equipment identification & state analysis based on the operating system files, application logs and specific backup data through experiments. The experimental results show data recording methods and contents differences between Huawei and Xiaomi smartphones. However, under the recording process, the two types of mobile phones will write data records related to the recording files in specific operating system files. Therefore, we can identify the original recording equipment of specific mobile phone recording files and their changes by analysing system files, application logs, and even the particular backup data. This method is effective for recording devices’ identification of ordinary and call recordings made by Huawei and Xiaomi Android smartphones and their state analysis; Furthermore, it can also be used for equipment identification & state analysis for Harmony OS recordings and other multimedia files in Android smartphones. Of course, since many mobile phone manufacturers have made secondary development of the Android operating system, we must continue research equipment identification & state analysis of recordings made by other Android smartphone brands.

Heat-induced fluorescence technology is a professional technology that can develop latent fingerprints on porous substrates without chemical reagents. Developing latent fingerprints on painted walls is a necessary application extension of this technology. Therefore, this paper focuses on exploring the reaction mechanism of the heat-induced fluorescence method of the latent fingerprint on the painted wall. On this basis, taking the painted wall as the object of trace-bearing, the influence of the heating distance, time length, temperature, coating type, and the aging degree of the latent fingerprint on the developing effect was gradually studied by using the control variable method. Finally, the best conditions of the latent fingerprint on the painted wall were obtained as follows: the heating distance of 15 cm, the heating time of 5 minutes, and the heating temperature of 500℃; the type of coating does not affect the effect of the heat-induced fluorescence technology to develop the latent fingerprints on the wall, and the long-dated latent fingerprints still have a good result. Technical research can provide technical support for developing latent fingerprints on the wall at the scene of criminal cases.

The fingerprint analysis of age is one of the important research directions in the field of forensic science, but there are some problems with various existing analysis methods, such as strong subjective experience, low feature utilization, small sample size and poor classification effect. To solve the above problems, an age classification model based on random forest algorithm was proposed. Firstly, the right-hand fingerprint samples of 1 600 males (aged 11 to 76) were collected to quantitatively process the feature data that might change with age. Then, the correlation analysis between each feature’s data and individual age was carried out to screen for features that were significantly correlated with age. Finally, based on random forest, ExtraTrees, CatBoost, KNN and BP neural network algorithms, four and six age classification models were established respectively. The applicability of the random forest algorithm was evaluated by model comparison, and the importance ranking of characteristic variables was output. The experimental results show that the random forest algorithm is the best for classification among the five classification models, which are as follows: in the four-classification model, the classification accuracy of random forest is 0.812, and the Kappa coefficient is 0.738; in the six-classification model, the classification accuracy of random forest is 0.738, and the Kappa coefficient is 0.675. Therefore, the fingerprint age classification model based on the random forest algorithm proposed in this paper can judge the age range of individuals more scientifically and accurately, so as to provide clues and ranges for investigation and technical inspection.

Freeze drying technology can remove about 99% moisture from the substance, resulting in the freeze-dried product with an increased internal surface area, which is loose, porous, and easy to recover. These characteristics are very suitable for application in the PCR amplification kit of forensic STR examination. Lyophilized reagent could break the challenge of the upper limit of template addition in conventional PCR systems. This study aims to test the technical performance of DNATyper^TM 30 lyophilized reagent and evaluate its application ability in practical forensic cases. In order to test the detection rate, sensitivity, stability and other aspects of lyophilized reagents, an exploration was carried out by setting different storage conditions, time ranges and concentration gradient. In order to meet the needs of room temperature transportation, the reagents were placed at room temperature (23 °C to 25 °C) to simulate the transportation environment and compare the STR typing results at 1, 7, 15, 30 days. In sensitivity test, standard DNA 9947A was used as template and its gradient was set from 0.0313 ng to 2ng. Furthermore, three types of case samples were selected, including trace DNA sample, to test the practical application of lyophilized reagents and liquid reagents were used in parallel for comparison. The results showed that DNATyper^TM 30 lyophilized reagent had accurate typing results and the peak value was between 3000 and 20000 RFUs with good repeatability. The lyophilized reagent was validated to get a well-balanced STR typing result, and the sensitivity was 0.125 ng, while it showed good stability when stored at room temperature for over 1 month. Essentially, lyophilized reagents performed outstandingly in the detection of trace DNA samples, with a higher detection rate and higher peak height of loci compared to conventional reagents. Besides, compared to longer segment loci, lyophilized reagents had a higher detection rate for shorter segment loci. Overall, DNATyper^TM 30 lyophilized reagent, which is easy to operate and has a high sensitivity, can significantly increase the loading quantity of DNA tamplate, and extend the storage time at room temperature, and meet the needs of DNA tracing testing, long-distance transportation and room temperature carrying at the same time. Therefore, lyophilized reagents have broad prospects in forensic examination and good practical application value.

Lysergic acid diethylamide (LSD) is the most potent semi-artificial hallucinogenic agent currently known. Recreational LSD use became a central, highly-visible aspect of the 1960s youth counterculture movement, eventually paving the way for international prohibition in 1971. But nowadays, more and more criminals utilize chemical knowledge and advanced technology to modify the structure of controlled drugs and produce new psychoactive substances (NPSs) that are not controlled by law in order to escape legal sanctions. NPSs do great harm to human health. In recent years, several lysergamide derivatives have been distributed as NPSs in the world. In this study, we presented a method for the identification of the lysergic acid diethylamide analogue 1-cylopropanoyl-lysergic acid diethylamide seized for the first time in China by gas chromatography-mass spectrometry (GC-MS) and ultra performance liquid chromatography-electrospray ionization- quadrupole/electrostatic field-Orbitrap-mass spectrometry (UPLC-Q-Exactive Orbitrap-MS). Unknown sample was extracted with methanol and water, and the supernatant was taken and analyzed by GC-MS and UPLC-Q-Orbitrap-MS, while lysergic acid diethylamide (LSD) was studied as a contrast. By GC-MS detection, the main characteristic ion peaks of mass spectrometry fragments of unknown components with retention time of 23.85 min were m/z 221, 289, 391, 69, 181, 207, 249, 348. By UPLC-Q-Exactive Orbitrap-MS detection, the excimer ion peak of the unknown component with a retention time of 3.99 min is m/z 392.2328, and the main ion of the secondary mass spectrum were m/z 291.148 7, 349.190 4, 281.164 3, 265.133 3, 223.122 6, 208.075 3, 251.117 6. Based on the lack of reference substance, the target object was identified as 1-cylopropanoyl-lysergic acid diethylamide (1cP-LSD) after the SWGDRUG spectral library and Cayman spectral library search, the information comparison in the reported literature and the analysis of its high-resolution mass spectrometry data. The method is simple and rapid, and has a good application prospect, which can be used for the detection of actual cases. It fills the deficiency of domestic analysis of 1cP-LSD and increases the understanding of new LSD analogue drugs.

With the breakthrough of deep-learning technology in the field of artificial intelligence, deepfake portrait videos appear more and more frequently, such as facial tampering, pornographic video face swapping, changing politicians’ faces and making false statements, etc. This kind of deepfakes may pose a threat to societies; therefore, distinguishing deepfake videos from genuine ones has become an urgen issue. Lots of deepfake detection methods are carried out by constructing many data sets with different compression factors. At present, the deepfake detection technology based on deep-learning algorithm is popular, which requires lots of significant time consumption and massive computing power for training classification model. At the same time, the attributes of black box and unexplainability of deep learning networks also plague the researchers in forensic science. In order to solve the problem of authenticity forensics of the deepfake portrait videos, this paper takes portrait videos encoded by H.264/AVC as the research object, and proposes a method based on inter-frame quantization parameter intensity value to detect deepfake portrait videos and real portrait videos. The selection of inter-frame quantization parameter intensity value and the determination of the inter-frame quantization parameter intensity by binary Logistic regression equation are expounded in detail. The experimental results show favorable accuracy and robustness for the deepfake portrait videos synthesized by DeepFaceLab platform. The paper proposed an interpretable detection method for deepfake portrait videos, which is conducive to determine the direction of investigation and confirm the criminal facts. But there are some limitations. Firstly, the experimental samples are not rich enough. Secondly, the introduced method is greatly affected by video compression, which caused limited application scenarios. Thirdly, the analysis efficiency needs to be optimized.

For the analysis of the suspected drugs seized in a local case, and for the identification and characterization of the compound, this paper identified and characterized the target compound based on several techniques including gas chromatography-mass spectrometry (GC-MS), liquid chromatography-high resolution time-of-flight mass spectrometry (LC-QTOF), Fourier transform infrared spectroscopy (FT-IR), hydrogen nuclear magnetic resonance spectroscopy (¹H NMR), carbon nuclear magnetic resonance spectroscopy (¹³C NMR) and X-ray diffraction (XRD) of single crystal. The fragment information and neutral loss mass spectrum of ketamine and F-ketamine were determined and compared with the target compound. Based on the characterization results and neutral loss mass spectrum, the compound possesses bromine stable isotopes and a similar structure with ketamine and F-ketamine, which has been identified as Br-ketamine. Ketamine, one of the most widely abused drugs, and its derivative F-ketamine (2-FDCK) have been both forbidden by the Chinese government. To avoid the legal sanction, drug criminals usually modify the chemical structures of old drugs. It can be expected that Br-ketamine has some risks of drug abuse. However, there was no relevant research on characterization, psychoactivity, addiction and physiological toxicity. Therefore, this work provides identification and characterization of Br-ketamine, a new phencyclidine derivative. On one hand, this work provides significant references for the identification of Br-ketamine and further research. On another hand, the proposed identification method using neutral loss mass spectra can also be applied to other unknown compounds.

Paralytic shellfish poisoning is globally among the most commonly-seen poisoning incidents resulted from shellfish, posing huge threat to people’s life and health with its widest distribution, greatest harm and highest mortality (its oral-lethal dose less than 1mg for human). Paralytic shellfish poisoning is caused from the highly-toxic paralytic toxins of shellfish. The paralytic shellfish toxins (PSTs) are able to paralyze nerves and muscles and affect both the nerval and cardiovascular systems. PSTs have many kinds and structure-similar derivatives that can transform into one another, hence conducing difficulties to detect them. A review was here carried out into the PSTs about their properties, mechanism of action, toxic symptoms and metabolic pathways, having summarized the relating pretreatment methods of solid-phase extraction, dispersive solid-phase extraction and immunoaffinity chromatography, and successively discussed the applicable detection choices including the biologically-infected mouse approach, immunoassay, liquid-chromatography fluorescent detection and liquid chromatography-mass spectrometry. Therefore, valuable references should be capable of providing with this review for the concerned people to research PSTs, develop and improve relevant detection performance, examine correlative forensic-significant toxins and stipulate involving norms and standards.

This study is aimed to fully explore the “time scale” role of hair samples in forensic science, provide technical methods for fine forensic analysis of hair samples, and offer reference examples for the description of drug history and criminal investigation of estazolam, a benzodiazepine antipsychotic. Actual hair samples were collected from adult estazolam users for time-sharing and sectional quantitative examination. Hairs were fixed and divided at the millimetre level using double-sided tape and a paper cutter. The hair-grinding extracts were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The content of estazolam was determined by the internal standard curve method with diazepam-d5 as the internal standard. The limit of quantitation (LOQ) was 0.4 pg/mg for the hair segments above 1 cm and 2 pg/mg for the millimetre scale ones, respectively. The content distribution of estazolam along the hair shaft was investigated under long-term use, short-term use and drug withdrawal conditions. After a single dose of estazolam, continuous shaving sampling and analysis were carried out on 2 volunteers to monitor the dynamic process of estazolam in the hair growing out of the skin. In the hair samples collected in this study, after long-term treatment (more than 2 years), the highest content of estazolam was located in the near root or middle segments, and there was a general loss in the end segments. Hair dyeing and perm can change the hair matrix, leading to an accelerated loss from estazolam out of the hair. Under a single dose and short-term administration, there was a corresponding relationship between the concentrated distribution zone of estazolam and the time of administration, which shifted distally with the hair growth. The peak spacing could be used to estimate the hair growth rate of the subjects. After drug withdrawal, the content of estazolam decreased slowly from the hair tip to the hair root, and the elimination of estazolam in the proximal hair segment took more than 3 months. Shaved moustache samples may be deeply contaminated by self-sebum and sweat, resulting in the highest content occurring on the next day of drug administration. In different subjects, there was a positive correlation between the peak content of estazolam and the dose in the corresponding period. The peak contents of estazolam were generally higher than 60 pg/mg under long-term medication (above 7 mg per week) and lower than 20 pg/mg under single dose (1 mg or less) and short-term medication. The time-sharing and segmented test of hair can help to explore the time-space distribution of estazolam after it enters the body and provides theoretical and technical support for donor behavior association and drug history description.

Single nucleotide polymorphism (SNP) profiling is a commonly used genetic tool for individual identification and ancestry inference in forensic genetics. This study was constructed based on the whole genome SNP data of 163 Mongolian individuals from Inner Mongolia region of China and 777 individuals from 13 other populations in China. PLINK and ADMIXTURE software was used to analyze the genetic structure of these populations. Plink software was used for Genome Wide Association Studies to screen Mongolian specific SNPs. The DAA software was used to calculate the population matching probability, likelihood ratio and ancestral components of the reference population and 569 individuals from 7 test populations to evaluate the accuracy of the inference model. The results of population genetic structure analysis showed that the Mongolian population is mainly composed of northern East Asian component, and is closely clustered with other Altaic populations. 644 Mongolian specific AISNP loci were screened. Among the reference populations, the inference accuracy of the Mongolian population was 98.16%, and the other populations were 100%. Among the test populations, the accuracy of the Mongolian population was 86.67%, and the other populations were 96.15% to 100%. This study indicates that there are genetic structure differences between the Mongolian population and other East Asian subpopulations. The 644 selected AISNP loci can be used for genetic inference between the Mongolian population and other East Asian subpopulations, which is of great significance for improved ancestry inference within East Asia.

For many speech technologies, it is required to have only one speaker in a complete statement, or it will degrade the performance of the algorithm. Therefore, speaker diarization becomes an important front-end for this system in the presence of multiple speakers. In order to improve the performance of the speaker diarization system, in this study, a d-vector based speaker binarization method is proposed, which is trained by a generalized end-to-end (GE2E) loss function that achieves better performance on speakers verification tasks. Firstly, the GE2E loss function is used to train a deep neural network (DNN) based on long short-term memory (LSTM) to extract the speaker-discriminative embeddings (d-vector), which is a neural network based on audio embeddings. Secondly, reference speech segments of each speaker are extracted from the input audio file and their embeddings are trained separately. While training continuous embeddings of the entire audio file, the cosine similarity of these continuous embeddings to the speakers’ embeddings is computed. Finally, the segments with a cosine similarity score greater than 0.75 are stored in the audio file of the corresponding speaker. This method adopts the principle of first recognition and then segmentation, and experimental results show that the algorithm has excellent performance in the scene where the number of speakers can be predicted and the short speech of single speakers can be easily obtained. Therefore, it can be used in multi-speaker automatic recognition system to automatically segment the target speaker’s voice to improve the performance.

Leaking LPG (liquefied petroleum gas) is prone to cause poisoning and even explosion accident, consequently potential of inflicting loss to people’s life and property. Therefore, it is necessary to explore the rules of diffusion and distributing concentration of leaking LPG in a confined space so as to provide a theoretical basis about prevention and tackling those involving indoor explosion accidents. Through the field simulation test of different LPG’s leakage conditions and numerical imitation calculation, a survey was here carried out into the changes of spatial concentrations of LPG under every selected testing condition. The results indicated that the diffusion of LPG was greatly influenced by gravity, having the higher concentrated LPG appeared at the lower part and/or near the wall in the tested space. LPG was observed of linearly increasing its concentration with time in the testing closed space under the following scenarios: the space where LPG was diffused from a leaking pipe and at the concentration less than 10%; the places comparatively far away from the leaking point that was located on a gas stove. For the leaking pipe, the spatial LPG’s concentration reached its critical explosion limit and beyond in shorter time, with the prolonged LPG leakage having brought forth the explosion-enabling range first expanding then reducing. For the leaking from a gas stove, the gas was gradually accumulated around the leaking point where the gas concentration was kept within the explosion-enabling range (appearing to take the gas stove as its center and slowly expand outwards into the space) for a long time. When the confined space tested let its window open, the explosion-enabling range was shown of reducing yet the explosion-enabling concentration there was maintained for a much-elongated duration.

With the widespread application of printing equipment, such as office equipment, and the development of printing technology, the conventional inspection methods, which take substantive paper documents as the analysis object and take morphological characteristics and chemical properties as the analysis points, have been unable to meet all the needs of printing document identification. At present, the method of transforming printed documents into digital images by using image capture devices such as flat-panel scanners and digital cameras has become a hot spot in the field of document identification. In many cases, files are either actively or passively converted into images for storage, and the domestic inspection standards for paper carriers cannot be applied to the inspection of such files based on digital images. The ISO/IEC 24790 standard comprehensively covers the quality inspection methods of images printed by office imaging systems, which may enrich the inspection methods of digital printed documents in China and promote the construction of digital inspection standards. This paper interprets the international standard ISO/IEC 24790, identifies the reference modes for domestic standards, and elaborates the applicability of the evaluation methods for large area graphic image quality attributes, character and line image quality attributes introduced in international standards. However, the road of quantification is still in the early stage for China. At this stage, it is necessary to consider the correlation between attributes and document inspection and the measurement accuracy of the instrument when introducing the physical indicators in the standard into document identification. Undeniably, the introduction of the international standard ISO/IEC 24790 and the establishment of a comprehensive evaluation method that reflects the relationship between the perceptual characteristics of human visual system and the physical properties of images have provided new impetus for quantitative construction.

Detecting of the single-nucleotide polymorphisms of Y-chromosome (Y-SNP) is particularly useful in the identification of paternal lineages for forensic evidences under investigation. To evaluate the technical performance in Y-SNP detection and its forensic applicability of the Ion AmpliSeq HID Y-SNP Research Panel V1 Kit, this study tested the kit from the aspects of sequencing performance, repeatability and sensitivity using pedigree samples and the Control DNA 9948. Forty four samples from one male family with clear genetic relationships but have Y-STR mutations were detected by Ion AmpliSeq HID Y-SNP Research Panel V1 Kit on the Ion GeneStudio S5 Plus next generation sequencing platform, and serials diluted 9948 DNA samples were also sequenced in parallel. The sequencing results showed that each run of sequencing produced no less than1.97 Gb of data, more than 99% of the sequences in alignment. An average of 845 Y-SNP (98.37%) loci could be used for subsequent analysis, and the sequencing results were proved to be reliable. The Y-SNP sequencing results of the Control DNA 9948 were consistent, repeatable, and the sensitivity of this Y-SNP detecting kit could be as low as 100 pg. High resolution Y-SNP haplogroups were obtained for all the pedigree samples tested, and the Y-SNP haplogroup analysis results were consistent. Therefore, the Ion Ampliseq HID Y-SNP Research Panel V1 Kit has excellent sequencing performance, high sensitivity and good repeatability, and can be used as a supplementary method for pedigree screening in forensic casework.

Writing robot is a kind of writing equipment; it came into being with the development of electronic engraving technology, 3D printing technology and computer simulation technology. According to their different structures, they can be divided into three types: straight joint writing robot, bending joint writing robot, planar joint writing robot. In recent years, due to the low price and good writing effect of the writing robot, this device has become popular, and may be used by some people to forge handwriting. Its potential risks have not only attracted the attention of domestic handwriting examiners, but also attracted the attention of some foreign handwriting examiners. For this problem, they conducted a lot of experimental research and theoretical discussion from the perspective of graphology. Based on the published papers at home and abroad, this paper first summarizes the types of writing robots and their respective working principles, and then summarizes the characteristics of the handwriting written by straight joint writing robots and bending joint writing robot. On this basis, four methods for recognizing robot handwriting are introduced, they are: overall feature recognition, detailed feature observation, analysis of handwriting overlap comparison, and computer automatic recognition. At the same time, this paper summarizes the social evaluation of robot’s ability to imitate human’s handwriting. Finally, it points out some problems existing in the existing research, which are mainly manifested in two aspects: first, there is a lack of in-depth analysis and research on the influencing factors of handwriting characteristics of writing robots, especially the lack of correlation analysis on how various writing parameters affect handwriting characteristics; second, there is a lack of necessary tracking research on some new writing robots. In view of these problems, the future research trend in this field is prospected, and the development trend of this equipment should be closely watched to prevent potential risks.

Whether the suspicious handwriting is written or not is the key in the handwritirg examination, which directly determines the conclusion. The traditional methods of forging handwriting, inclicding printing, copying and stamping, are easy to identify, because there are no stroke pressure. But the advances in robotic writing technology pose new challenges for forensic document examiners. Robotic writing can form three-dimensional stroke indentation, and it is easy to misjudge the handwriting formed by normal writing in the examination. Some researchers have modified the Cartesian writing robot to make its handwriting more natural, and more similar to the handwriting written by human, which is difficult to distinguish. Forensic document examiners should be alert to this kind of high-level forged handwriting. In this study, by utilizing the optical tomography and depth-of-field technology of AB 8000 handwriting quantitative tester, we measured the strokes of natural handwriting samples and high-level robotic writing samples, and obtained the width and depth of stroke, calculated the ratio i of the horizontal distance between the deepest mark and the edge of stroke and the width of stroke ink. We alsa measured the distribution degree of i value by chart and differential value operation, and analyzed the aggregation and fluctuation of the mark angles between high-level robotic writing samples and human handwriting samples. The results showed that the stroke angle of high-level robotic writing samples has high aggregation and low volatility, while the stroke angle of human writing samples has low aggregation and high volatility. Therefore, it is verified the validity of stroke angle feature in recognizing the robotic writing. It is also observed in the experiment that the stroke angle of long strokes is more stable, and the angle data of turning strokes and crossing strokes will be disturbed, so it is more accurate to choose long strokes for measurement.

The occurrence of famous fingerprint identification errors, such as the McKie case in the UK and the Madrid train bombing case in Spain, has triggered an increase in the scientific requirements for fingerprint evidence, and the industry is in urgent need of basic theoretical research on close non-matches (CNMs). In addition, with the continuous expansion of the fingerprint database, the fingerprints screened by automatic fingerprint identification system with the highest scores are highly similar to the fingermarks, and the identification risks brought by CNMs are constantly amplified. The problem of CNMs has become one of the important research contents in the field of fingerprint inspection, which is of great significance to the construction of fingerprint identification standards. In this paper, firstly, the research background of CNMs is expounded with the Madrid train bombing case. Secondly, the concept of CNMs and a peer-reviewed standard are introduced. Then, the causes of CNMs (mainly monozygotic twins and automatic fingerprint identification system), the false positive error rate and the causes of identification errors are comprehensively and deeply analyzed and summarized. Finally, combined with the research status, some prospects for its future development trend are put forward, with a view to supplementing the basic theory of fingerprint identification and providing some reference for the quantitative evaluation of fingerprint evidence.

Based on a large number of forensic and related medical literature and bioinformatics databases, the purpose of this study is to explore the expression differences of non-coding Piwi-interacting RNA (piRNA) molecules in common forensic body fluids, evaluate the body fluid differentiation ability of target molecules by statistical analysis, and establish a suitable model of identification method, so as to provide a method supplement for the identification of common body fluids (spots) in forensic genetics. In this study, we collected 120 human common body fluid samples in forensic genetics (including peripheral blood, menstrual blood, semen, saliva and vaginal secretion), and the expression of target piRNA molecules in five kinds of body fluids was detected by real-time fluorescent quantitative PCR method. To determine the applicable internal reference genes, the stability of the three internal parameters in five kinds of body fluids was evaluated by Genorm, NormFinder, BestKeeper software and ΔCt four methods. The difference of relative expression ΔCq of each marker in different body fluids was analyzed, and the marker molecules which can be used to distinguish body fluids were screened. At the same time, aiming at the difficult problem of distinguishing between saliva and vaginal secretion in forensic application, three piRNA molecules were identified and combined to establish a support vector machine (SVM) classification model to identify saliva and vaginal secretion. In addition, the stability of these small molecules was evaluated by detecting the relative expression of piRNAs in simulated case samples dried at room temperature for 1 month, 6 months, 12 months and ultraviolet irradiation for 12 hours and 48 hours, respectively. Finally, in this study, nine marker molecules were screened for body fluids identification, which were piR-33043, piR-33151, piR-57125, piR-31662, piR-31068, piR-31925, piR-43771, piR-43773, piR-55521, and the piR-33151, piR-31662 and piR-31925 three piRNA molecules combination was established as a SVM classification model to effectively distinguish saliva and vaginal secretion with an accuracy of 100%. These three piRNA molecules could still be detected in samples dried indoors for 12 months or UV irradiation for 48 hours. The results of this study show that there were significant differences in the relative expression of piRNA molecules in different body fluids. PiRNA molecules have the ability to identify common types of body fluids in forensic genetics, and the established classification model can effectively and accurately distinguish saliva and vaginal secretion, which has high application potential.

Detecting and identifying the combustion promoter residue in the fire site sample is a difficult task. The fire combustion process may be accompanied by pyrolysis, weathering/evaporation or microbial degradation of the combustion agent, etc., making the collection of residues difficult, and the subsequent identification of the fire combustion agent material evidence also brings interference, so it is very important to determine the nature of the fire and find out the cause of the fire in a timely and accurate manner whether there are diesel and other combustion aids at the fire scene. In this paper, polyethylene (PE) plastic products-plastic wrap and polyethylene raw materials were used as research objects to explore the influence of them on the analysis and identification of diesel fuel, an ignition booster at the scene of arson. Solid phase microextraction-gas chromatography mass spectrometry (SPME-GC-MS) was used to compare and analyze the characteristic spectra of samples and diesel fuel in three different combustion states: bulk body, incomplete combustion, complete combustion to spontaneous combustion extinguishing. Through the comparative analysis of polyethylene raw materials and PE plastic wrap body, it is found that the main components contained in the two components are basically the same, and the individual components contained in PE plastic wrap are not detected in polyethylene raw materials, mainly due to the addition of some additives in the production process of PE plastic wrap. Incomplete combustion of plastic wrap in the three combustion states has the greatest effect on diesel. When m/z=85, 178, 192, 183, the two contain the same components and the distribution law is basically the same, but when the ion m/z=83 is extracted, the sample of incomplete combustion plastic wrap does not contain the same naphthene as diesel. The application of SPME-GC-MS technology can distinguish incomplete combustion plastic wrap from diesel, which is convenient and fast, has high sensitivity and fast analysis speed, and can be used as a preferred method for experimental preliminary screening, which is suitable for the analysis of combustion promoters in the fire field.